Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

13 files changed, 11897 insertions, 0 deletions

diff --git a/src/database/sql/convert.go b/src/database/sql/convert.go
new file mode 100644
index 0000000..b966ef9
--- /dev/null
+++ b/src/database/sql/convert.go
@@ -0,0 +1,599 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Type conversions for Scan.
+
+package sql
+
+import (
+	"database/sql/driver"
+	"errors"
+	"fmt"
+	"reflect"
+	"strconv"
+	"time"
+	"unicode"
+	"unicode/utf8"
+)
+
+var errNilPtr = errors.New("destination pointer is nil") // embedded in descriptive error
+
+func describeNamedValue(nv *driver.NamedValue) string {
+	if len(nv.Name) == 0 {
+		return fmt.Sprintf("$%d", nv.Ordinal)
+	}
+	return fmt.Sprintf("with name %q", nv.Name)
+}
+
+func validateNamedValueName(name string) error {
+	if len(name) == 0 {
+		return nil
+	}
+	r, _ := utf8.DecodeRuneInString(name)
+	if unicode.IsLetter(r) {
+		return nil
+	}
+	return fmt.Errorf("name %q does not begin with a letter", name)
+}
+
+// ccChecker wraps the driver.ColumnConverter and allows it to be used
+// as if it were a NamedValueChecker. If the driver ColumnConverter
+// is not present then the NamedValueChecker will return driver.ErrSkip.
+type ccChecker struct {
+	cci  driver.ColumnConverter
+	want int
+}
+
+func (c ccChecker) CheckNamedValue(nv *driver.NamedValue) error {
+	if c.cci == nil {
+		return driver.ErrSkip
+	}
+	// The column converter shouldn't be called on any index
+	// it isn't expecting. The final error will be thrown
+	// in the argument converter loop.
+	index := nv.Ordinal - 1
+	if c.want <= index {
+		return nil
+	}
+
+	// First, see if the value itself knows how to convert
+	// itself to a driver type. For example, a NullString
+	// struct changing into a string or nil.
+	if vr, ok := nv.Value.(driver.Valuer); ok {
+		sv, err := callValuerValue(vr)
+		if err != nil {
+			return err
+		}
+		if !driver.IsValue(sv) {
+			return fmt.Errorf("non-subset type %T returned from Value", sv)
+		}
+		nv.Value = sv
+	}
+
+	// Second, ask the column to sanity check itself. For
+	// example, drivers might use this to make sure that
+	// an int64 values being inserted into a 16-bit
+	// integer field is in range (before getting
+	// truncated), or that a nil can't go into a NOT NULL
+	// column before going across the network to get the
+	// same error.
+	var err error
+	arg := nv.Value
+	nv.Value, err = c.cci.ColumnConverter(index).ConvertValue(arg)
+	if err != nil {
+		return err
+	}
+	if !driver.IsValue(nv.Value) {
+		return fmt.Errorf("driver ColumnConverter error converted %T to unsupported type %T", arg, nv.Value)
+	}
+	return nil
+}
+
+// defaultCheckNamedValue wraps the default ColumnConverter to have the same
+// function signature as the CheckNamedValue in the driver.NamedValueChecker
+// interface.
+func defaultCheckNamedValue(nv *driver.NamedValue) (err error) {
+	nv.Value, err = driver.DefaultParameterConverter.ConvertValue(nv.Value)
+	return err
+}
+
+// driverArgsConnLocked converts arguments from callers of Stmt.Exec and
+// Stmt.Query into driver Values.
+//
+// The statement ds may be nil, if no statement is available.
+//
+// ci must be locked.
+func driverArgsConnLocked(ci driver.Conn, ds *driverStmt, args []interface{}) ([]driver.NamedValue, error) {
+	nvargs := make([]driver.NamedValue, len(args))
+
+	// -1 means the driver doesn't know how to count the number of
+	// placeholders, so we won't sanity check input here and instead let the
+	// driver deal with errors.
+	want := -1
+
+	var si driver.Stmt
+	var cc ccChecker
+	if ds != nil {
+		si = ds.si
+		want = ds.si.NumInput()
+		cc.want = want
+	}
+
+	// Check all types of interfaces from the start.
+	// Drivers may opt to use the NamedValueChecker for special
+	// argument types, then return driver.ErrSkip to pass it along
+	// to the column converter.
+	nvc, ok := si.(driver.NamedValueChecker)
+	if !ok {
+		nvc, ok = ci.(driver.NamedValueChecker)
+	}
+	cci, ok := si.(driver.ColumnConverter)
+	if ok {
+		cc.cci = cci
+	}
+
+	// Loop through all the arguments, checking each one.
+	// If no error is returned simply increment the index
+	// and continue. However if driver.ErrRemoveArgument
+	// is returned the argument is not included in the query
+	// argument list.
+	var err error
+	var n int
+	for _, arg := range args {
+		nv := &nvargs[n]
+		if np, ok := arg.(NamedArg); ok {
+			if err = validateNamedValueName(np.Name); err != nil {
+				return nil, err
+			}
+			arg = np.Value
+			nv.Name = np.Name
+		}
+		nv.Ordinal = n + 1
+		nv.Value = arg
+
+		// Checking sequence has four routes:
+		// A: 1. Default
+		// B: 1. NamedValueChecker 2. Column Converter 3. Default
+		// C: 1. NamedValueChecker 3. Default
+		// D: 1. Column Converter 2. Default
+		//
+		// The only time a Column Converter is called is first
+		// or after NamedValueConverter. If first it is handled before
+		// the nextCheck label. Thus for repeats tries only when the
+		// NamedValueConverter is selected should the Column Converter
+		// be used in the retry.
+		checker := defaultCheckNamedValue
+		nextCC := false
+		switch {
+		case nvc != nil:
+			nextCC = cci != nil
+			checker = nvc.CheckNamedValue
+		case cci != nil:
+			checker = cc.CheckNamedValue
+		}
+
+	nextCheck:
+		err = checker(nv)
+		switch err {
+		case nil:
+			n++
+			continue
+		case driver.ErrRemoveArgument:
+			nvargs = nvargs[:len(nvargs)-1]
+			continue
+		case driver.ErrSkip:
+			if nextCC {
+				nextCC = false
+				checker = cc.CheckNamedValue
+			} else {
+				checker = defaultCheckNamedValue
+			}
+			goto nextCheck
+		default:
+			return nil, fmt.Errorf("sql: converting argument %s type: %v", describeNamedValue(nv), err)
+		}
+	}
+
+	// Check the length of arguments after conversion to allow for omitted
+	// arguments.
+	if want != -1 && len(nvargs) != want {
+		return nil, fmt.Errorf("sql: expected %d arguments, got %d", want, len(nvargs))
+	}
+
+	return nvargs, nil
+
+}
+
+// convertAssign is the same as convertAssignRows, but without the optional
+// rows argument.
+func convertAssign(dest, src interface{}) error {
+	return convertAssignRows(dest, src, nil)
+}
+
+// convertAssignRows copies to dest the value in src, converting it if possible.
+// An error is returned if the copy would result in loss of information.
+// dest should be a pointer type. If rows is passed in, the rows will
+// be used as the parent for any cursor values converted from a
+// driver.Rows to a *Rows.
+func convertAssignRows(dest, src interface{}, rows *Rows) error {
+	// Common cases, without reflect.
+	switch s := src.(type) {
+	case string:
+		switch d := dest.(type) {
+		case *string:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = s
+			return nil
+		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = []byte(s)
+			return nil
+		case *RawBytes:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = append((*d)[:0], s...)
+			return nil
+		}
+	case []byte:
+		switch d := dest.(type) {
+		case *string:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = string(s)
+			return nil
+		case *interface{}:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = cloneBytes(s)
+			return nil
+		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = cloneBytes(s)
+			return nil
+		case *RawBytes:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = s
+			return nil
+		}
+	case time.Time:
+		switch d := dest.(type) {
+		case *time.Time:
+			*d = s
+			return nil
+		case *string:
+			*d = s.Format(time.RFC3339Nano)
+			return nil
+		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = []byte(s.Format(time.RFC3339Nano))
+			return nil
+		case *RawBytes:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = s.AppendFormat((*d)[:0], time.RFC3339Nano)
+			return nil
+		}
+	case decimalDecompose:
+		switch d := dest.(type) {
+		case decimalCompose:
+			return d.Compose(s.Decompose(nil))
+		}
+	case nil:
+		switch d := dest.(type) {
+		case *interface{}:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = nil
+			return nil
+		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = nil
+			return nil
+		case *RawBytes:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = nil
+			return nil
+		}
+	// The driver is returning a cursor the client may iterate over.
+	case driver.Rows:
+		switch d := dest.(type) {
+		case *Rows:
+			if d == nil {
+				return errNilPtr
+			}
+			if rows == nil {
+				return errors.New("invalid context to convert cursor rows, missing parent *Rows")
+			}
+			rows.closemu.Lock()
+			*d = Rows{
+				dc:          rows.dc,
+				releaseConn: func(error) {},
+				rowsi:       s,
+			}
+			// Chain the cancel function.
+			parentCancel := rows.cancel
+			rows.cancel = func() {
+				// When Rows.cancel is called, the closemu will be locked as well.
+				// So we can access rs.lasterr.
+				d.close(rows.lasterr)
+				if parentCancel != nil {
+					parentCancel()
+				}
+			}
+			rows.closemu.Unlock()
+			return nil
+		}
+	}
+
+	var sv reflect.Value
+
+	switch d := dest.(type) {
+	case *string:
+		sv = reflect.ValueOf(src)
+		switch sv.Kind() {
+		case reflect.Bool,
+			reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+			reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
+			reflect.Float32, reflect.Float64:
+			*d = asString(src)
+			return nil
+		}
+	case *[]byte:
+		sv = reflect.ValueOf(src)
+		if b, ok := asBytes(nil, sv); ok {
+			*d = b
+			return nil
+		}
+	case *RawBytes:
+		sv = reflect.ValueOf(src)
+		if b, ok := asBytes([]byte(*d)[:0], sv); ok {
+			*d = RawBytes(b)
+			return nil
+		}
+	case *bool:
+		bv, err := driver.Bool.ConvertValue(src)
+		if err == nil {
+			*d = bv.(bool)
+		}
+		return err
+	case *interface{}:
+		*d = src
+		return nil
+	}
+
+	if scanner, ok := dest.(Scanner); ok {
+		return scanner.Scan(src)
+	}
+
+	dpv := reflect.ValueOf(dest)
+	if dpv.Kind() != reflect.Ptr {
+		return errors.New("destination not a pointer")
+	}
+	if dpv.IsNil() {
+		return errNilPtr
+	}
+
+	if !sv.IsValid() {
+		sv = reflect.ValueOf(src)
+	}
+
+	dv := reflect.Indirect(dpv)
+	if sv.IsValid() && sv.Type().AssignableTo(dv.Type()) {
+		switch b := src.(type) {
+		case []byte:
+			dv.Set(reflect.ValueOf(cloneBytes(b)))
+		default:
+			dv.Set(sv)
+		}
+		return nil
+	}
+
+	if dv.Kind() == sv.Kind() && sv.Type().ConvertibleTo(dv.Type()) {
+		dv.Set(sv.Convert(dv.Type()))
+		return nil
+	}
+
+	// The following conversions use a string value as an intermediate representation
+	// to convert between various numeric types.
+	//
+	// This also allows scanning into user defined types such as "type Int int64".
+	// For symmetry, also check for string destination types.
+	switch dv.Kind() {
+	case reflect.Ptr:
+		if src == nil {
+			dv.Set(reflect.Zero(dv.Type()))
+			return nil
+		}
+		dv.Set(reflect.New(dv.Type().Elem()))
+		return convertAssignRows(dv.Interface(), src, rows)
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		if src == nil {
+			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
+		}
+		s := asString(src)
+		i64, err := strconv.ParseInt(s, 10, dv.Type().Bits())
+		if err != nil {
+			err = strconvErr(err)
+			return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
+		}
+		dv.SetInt(i64)
+		return nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		if src == nil {
+			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
+		}
+		s := asString(src)
+		u64, err := strconv.ParseUint(s, 10, dv.Type().Bits())
+		if err != nil {
+			err = strconvErr(err)
+			return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
+		}
+		dv.SetUint(u64)
+		return nil
+	case reflect.Float32, reflect.Float64:
+		if src == nil {
+			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
+		}
+		s := asString(src)
+		f64, err := strconv.ParseFloat(s, dv.Type().Bits())
+		if err != nil {
+			err = strconvErr(err)
+			return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
+		}
+		dv.SetFloat(f64)
+		return nil
+	case reflect.String:
+		if src == nil {
+			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
+		}
+		switch v := src.(type) {
+		case string:
+			dv.SetString(v)
+			return nil
+		case []byte:
+			dv.SetString(string(v))
+			return nil
+		}
+	}
+
+	return fmt.Errorf("unsupported Scan, storing driver.Value type %T into type %T", src, dest)
+}
+
+func strconvErr(err error) error {
+	if ne, ok := err.(*strconv.NumError); ok {
+		return ne.Err
+	}
+	return err
+}
+
+func cloneBytes(b []byte) []byte {
+	if b == nil {
+		return nil
+	}
+	c := make([]byte, len(b))
+	copy(c, b)
+	return c
+}
+
+func asString(src interface{}) string {
+	switch v := src.(type) {
+	case string:
+		return v
+	case []byte:
+		return string(v)
+	}
+	rv := reflect.ValueOf(src)
+	switch rv.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return strconv.FormatInt(rv.Int(), 10)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		return strconv.FormatUint(rv.Uint(), 10)
+	case reflect.Float64:
+		return strconv.FormatFloat(rv.Float(), 'g', -1, 64)
+	case reflect.Float32:
+		return strconv.FormatFloat(rv.Float(), 'g', -1, 32)
+	case reflect.Bool:
+		return strconv.FormatBool(rv.Bool())
+	}
+	return fmt.Sprintf("%v", src)
+}
+
+func asBytes(buf []byte, rv reflect.Value) (b []byte, ok bool) {
+	switch rv.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return strconv.AppendInt(buf, rv.Int(), 10), true
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		return strconv.AppendUint(buf, rv.Uint(), 10), true
+	case reflect.Float32:
+		return strconv.AppendFloat(buf, rv.Float(), 'g', -1, 32), true
+	case reflect.Float64:
+		return strconv.AppendFloat(buf, rv.Float(), 'g', -1, 64), true
+	case reflect.Bool:
+		return strconv.AppendBool(buf, rv.Bool()), true
+	case reflect.String:
+		s := rv.String()
+		return append(buf, s...), true
+	}
+	return
+}
+
+var valuerReflectType = reflect.TypeOf((*driver.Valuer)(nil)).Elem()
+
+// callValuerValue returns vr.Value(), with one exception:
+// If vr.Value is an auto-generated method on a pointer type and the
+// pointer is nil, it would panic at runtime in the panicwrap
+// method. Treat it like nil instead.
+// Issue 8415.
+//
+// This is so people can implement driver.Value on value types and
+// still use nil pointers to those types to mean nil/NULL, just like
+// string/*string.
+//
+// This function is mirrored in the database/sql/driver package.
+func callValuerValue(vr driver.Valuer) (v driver.Value, err error) {
+	if rv := reflect.ValueOf(vr); rv.Kind() == reflect.Ptr &&
+		rv.IsNil() &&
+		rv.Type().Elem().Implements(valuerReflectType) {
+		return nil, nil
+	}
+	return vr.Value()
+}
+
+// decimal composes or decomposes a decimal value to and from individual parts.
+// There are four parts: a boolean negative flag, a form byte with three possible states
+// (finite=0, infinite=1, NaN=2), a base-2 big-endian integer
+// coefficient (also known as a significand) as a []byte, and an int32 exponent.
+// These are composed into a final value as "decimal = (neg) (form=finite) coefficient * 10 ^ exponent".
+// A zero length coefficient is a zero value.
+// The big-endian integer coefficient stores the most significant byte first (at coefficient[0]).
+// If the form is not finite the coefficient and exponent should be ignored.
+// The negative parameter may be set to true for any form, although implementations are not required
+// to respect the negative parameter in the non-finite form.
+//
+// Implementations may choose to set the negative parameter to true on a zero or NaN value,
+// but implementations that do not differentiate between negative and positive
+// zero or NaN values should ignore the negative parameter without error.
+// If an implementation does not support Infinity it may be converted into a NaN without error.
+// If a value is set that is larger than what is supported by an implementation,
+// an error must be returned.
+// Implementations must return an error if a NaN or Infinity is attempted to be set while neither
+// are supported.
+//
+// NOTE(kardianos): This is an experimental interface. See https://golang.org/issue/30870
+type decimal interface {
+	decimalDecompose
+	decimalCompose
+}
+
+type decimalDecompose interface {
+	// Decompose returns the internal decimal state in parts.
+	// If the provided buf has sufficient capacity, buf may be returned as the coefficient with
+	// the value set and length set as appropriate.
+	Decompose(buf []byte) (form byte, negative bool, coefficient []byte, exponent int32)
+}
+
+type decimalCompose interface {
+	// Compose sets the internal decimal value from parts. If the value cannot be
+	// represented then an error should be returned.
+	Compose(form byte, negative bool, coefficient []byte, exponent int32) error
+}
diff --git a/src/database/sql/convert_test.go b/src/database/sql/convert_test.go
new file mode 100644
index 0000000..2668a5e
--- /dev/null
+++ b/src/database/sql/convert_test.go
@@ -0,0 +1,600 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sql
+
+import (
+	"database/sql/driver"
+	"fmt"
+	"reflect"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+var someTime = time.Unix(123, 0)
+var answer int64 = 42
+
+type (
+	userDefined       float64
+	userDefinedSlice  []int
+	userDefinedString string
+)
+
+type conversionTest struct {
+	s, d interface{} // source and destination
+
+	// following are used if they're non-zero
+	wantint    int64
+	wantuint   uint64
+	wantstr    string
+	wantbytes  []byte
+	wantraw    RawBytes
+	wantf32    float32
+	wantf64    float64
+	wanttime   time.Time
+	wantbool   bool // used if d is of type *bool
+	wanterr    string
+	wantiface  interface{}
+	wantptr    *int64 // if non-nil, *d's pointed value must be equal to *wantptr
+	wantnil    bool   // if true, *d must be *int64(nil)
+	wantusrdef userDefined
+	wantusrstr userDefinedString
+}
+
+// Target variables for scanning into.
+var (
+	scanstr    string
+	scanbytes  []byte
+	scanraw    RawBytes
+	scanint    int
+	scanint8   int8
+	scanint16  int16
+	scanint32  int32
+	scanuint8  uint8
+	scanuint16 uint16
+	scanbool   bool
+	scanf32    float32
+	scanf64    float64
+	scantime   time.Time
+	scanptr    *int64
+	scaniface  interface{}
+)
+
+func conversionTests() []conversionTest {
+	// Return a fresh instance to test so "go test -count 2" works correctly.
+	return []conversionTest{
+		// Exact conversions (destination pointer type matches source type)
+		{s: "foo", d: &scanstr, wantstr: "foo"},
+		{s: 123, d: &scanint, wantint: 123},
+		{s: someTime, d: &scantime, wanttime: someTime},
+
+		// To strings
+		{s: "string", d: &scanstr, wantstr: "string"},
+		{s: []byte("byteslice"), d: &scanstr, wantstr: "byteslice"},
+		{s: 123, d: &scanstr, wantstr: "123"},
+		{s: int8(123), d: &scanstr, wantstr: "123"},
+		{s: int64(123), d: &scanstr, wantstr: "123"},
+		{s: uint8(123), d: &scanstr, wantstr: "123"},
+		{s: uint16(123), d: &scanstr, wantstr: "123"},
+		{s: uint32(123), d: &scanstr, wantstr: "123"},
+		{s: uint64(123), d: &scanstr, wantstr: "123"},
+		{s: 1.5, d: &scanstr, wantstr: "1.5"},
+
+		// From time.Time:
+		{s: time.Unix(1, 0).UTC(), d: &scanstr, wantstr: "1970-01-01T00:00:01Z"},
+		{s: time.Unix(1453874597, 0).In(time.FixedZone("here", -3600*8)), d: &scanstr, wantstr: "2016-01-26T22:03:17-08:00"},
+		{s: time.Unix(1, 2).UTC(), d: &scanstr, wantstr: "1970-01-01T00:00:01.000000002Z"},
+		{s: time.Time{}, d: &scanstr, wantstr: "0001-01-01T00:00:00Z"},
+		{s: time.Unix(1, 2).UTC(), d: &scanbytes, wantbytes: []byte("1970-01-01T00:00:01.000000002Z")},
+		{s: time.Unix(1, 2).UTC(), d: &scaniface, wantiface: time.Unix(1, 2).UTC()},
+
+		// To []byte
+		{s: nil, d: &scanbytes, wantbytes: nil},
+		{s: "string", d: &scanbytes, wantbytes: []byte("string")},
+		{s: []byte("byteslice"), d: &scanbytes, wantbytes: []byte("byteslice")},
+		{s: 123, d: &scanbytes, wantbytes: []byte("123")},
+		{s: int8(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: int64(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: uint8(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: uint16(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: uint32(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: uint64(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: 1.5, d: &scanbytes, wantbytes: []byte("1.5")},
+
+		// To RawBytes
+		{s: nil, d: &scanraw, wantraw: nil},
+		{s: []byte("byteslice"), d: &scanraw, wantraw: RawBytes("byteslice")},
+		{s: "string", d: &scanraw, wantraw: RawBytes("string")},
+		{s: 123, d: &scanraw, wantraw: RawBytes("123")},
+		{s: int8(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: int64(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: uint8(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: uint16(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: uint32(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: uint64(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: 1.5, d: &scanraw, wantraw: RawBytes("1.5")},
+		// time.Time has been placed here to check that the RawBytes slice gets
+		// correctly reset when calling time.Time.AppendFormat.
+		{s: time.Unix(2, 5).UTC(), d: &scanraw, wantraw: RawBytes("1970-01-01T00:00:02.000000005Z")},
+
+		// Strings to integers
+		{s: "255", d: &scanuint8, wantuint: 255},
+		{s: "256", d: &scanuint8, wanterr: "converting driver.Value type string (\"256\") to a uint8: value out of range"},
+		{s: "256", d: &scanuint16, wantuint: 256},
+		{s: "-1", d: &scanint, wantint: -1},
+		{s: "foo", d: &scanint, wanterr: "converting driver.Value type string (\"foo\") to a int: invalid syntax"},
+
+		// int64 to smaller integers
+		{s: int64(5), d: &scanuint8, wantuint: 5},
+		{s: int64(256), d: &scanuint8, wanterr: "converting driver.Value type int64 (\"256\") to a uint8: value out of range"},
+		{s: int64(256), d: &scanuint16, wantuint: 256},
+		{s: int64(65536), d: &scanuint16, wanterr: "converting driver.Value type int64 (\"65536\") to a uint16: value out of range"},
+
+		// True bools
+		{s: true, d: &scanbool, wantbool: true},
+		{s: "True", d: &scanbool, wantbool: true},
+		{s: "TRUE", d: &scanbool, wantbool: true},
+		{s: "1", d: &scanbool, wantbool: true},
+		{s: 1, d: &scanbool, wantbool: true},
+		{s: int64(1), d: &scanbool, wantbool: true},
+		{s: uint16(1), d: &scanbool, wantbool: true},
+
+		// False bools
+		{s: false, d: &scanbool, wantbool: false},
+		{s: "false", d: &scanbool, wantbool: false},
+		{s: "FALSE", d: &scanbool, wantbool: false},
+		{s: "0", d: &scanbool, wantbool: false},
+		{s: 0, d: &scanbool, wantbool: false},
+		{s: int64(0), d: &scanbool, wantbool: false},
+		{s: uint16(0), d: &scanbool, wantbool: false},
+
+		// Not bools
+		{s: "yup", d: &scanbool, wanterr: `sql/driver: couldn't convert "yup" into type bool`},
+		{s: 2, d: &scanbool, wanterr: `sql/driver: couldn't convert 2 into type bool`},
+
+		// Floats
+		{s: float64(1.5), d: &scanf64, wantf64: float64(1.5)},
+		{s: int64(1), d: &scanf64, wantf64: float64(1)},
+		{s: float64(1.5), d: &scanf32, wantf32: float32(1.5)},
+		{s: "1.5", d: &scanf32, wantf32: float32(1.5)},
+		{s: "1.5", d: &scanf64, wantf64: float64(1.5)},
+
+		// Pointers
+		{s: interface{}(nil), d: &scanptr, wantnil: true},
+		{s: int64(42), d: &scanptr, wantptr: &answer},
+
+		// To interface{}
+		{s: float64(1.5), d: &scaniface, wantiface: float64(1.5)},
+		{s: int64(1), d: &scaniface, wantiface: int64(1)},
+		{s: "str", d: &scaniface, wantiface: "str"},
+		{s: []byte("byteslice"), d: &scaniface, wantiface: []byte("byteslice")},
+		{s: true, d: &scaniface, wantiface: true},
+		{s: nil, d: &scaniface},
+		{s: []byte(nil), d: &scaniface, wantiface: []byte(nil)},
+
+		// To a user-defined type
+		{s: 1.5, d: new(userDefined), wantusrdef: 1.5},
+		{s: int64(123), d: new(userDefined), wantusrdef: 123},
+		{s: "1.5", d: new(userDefined), wantusrdef: 1.5},
+		{s: []byte{1, 2, 3}, d: new(userDefinedSlice), wanterr: `unsupported Scan, storing driver.Value type []uint8 into type *sql.userDefinedSlice`},
+		{s: "str", d: new(userDefinedString), wantusrstr: "str"},
+
+		// Other errors
+		{s: complex(1, 2), d: &scanstr, wanterr: `unsupported Scan, storing driver.Value type complex128 into type *string`},
+	}
+}
+
+func intPtrValue(intptr interface{}) interface{} {
+	return reflect.Indirect(reflect.Indirect(reflect.ValueOf(intptr))).Int()
+}
+
+func intValue(intptr interface{}) int64 {
+	return reflect.Indirect(reflect.ValueOf(intptr)).Int()
+}
+
+func uintValue(intptr interface{}) uint64 {
+	return reflect.Indirect(reflect.ValueOf(intptr)).Uint()
+}
+
+func float64Value(ptr interface{}) float64 {
+	return *(ptr.(*float64))
+}
+
+func float32Value(ptr interface{}) float32 {
+	return *(ptr.(*float32))
+}
+
+func timeValue(ptr interface{}) time.Time {
+	return *(ptr.(*time.Time))
+}
+
+func TestConversions(t *testing.T) {
+	for n, ct := range conversionTests() {
+		err := convertAssign(ct.d, ct.s)
+		errstr := ""
+		if err != nil {
+			errstr = err.Error()
+		}
+		errf := func(format string, args ...interface{}) {
+			base := fmt.Sprintf("convertAssign #%d: for %v (%T) -> %T, ", n, ct.s, ct.s, ct.d)
+			t.Errorf(base+format, args...)
+		}
+		if errstr != ct.wanterr {
+			errf("got error %q, want error %q", errstr, ct.wanterr)
+		}
+		if ct.wantstr != "" && ct.wantstr != scanstr {
+			errf("want string %q, got %q", ct.wantstr, scanstr)
+		}
+		if ct.wantbytes != nil && string(ct.wantbytes) != string(scanbytes) {
+			errf("want byte %q, got %q", ct.wantbytes, scanbytes)
+		}
+		if ct.wantraw != nil && string(ct.wantraw) != string(scanraw) {
+			errf("want RawBytes %q, got %q", ct.wantraw, scanraw)
+		}
+		if ct.wantint != 0 && ct.wantint != intValue(ct.d) {
+			errf("want int %d, got %d", ct.wantint, intValue(ct.d))
+		}
+		if ct.wantuint != 0 && ct.wantuint != uintValue(ct.d) {
+			errf("want uint %d, got %d", ct.wantuint, uintValue(ct.d))
+		}
+		if ct.wantf32 != 0 && ct.wantf32 != float32Value(ct.d) {
+			errf("want float32 %v, got %v", ct.wantf32, float32Value(ct.d))
+		}
+		if ct.wantf64 != 0 && ct.wantf64 != float64Value(ct.d) {
+			errf("want float32 %v, got %v", ct.wantf64, float64Value(ct.d))
+		}
+		if bp, boolTest := ct.d.(*bool); boolTest && *bp != ct.wantbool && ct.wanterr == "" {
+			errf("want bool %v, got %v", ct.wantbool, *bp)
+		}
+		if !ct.wanttime.IsZero() && !ct.wanttime.Equal(timeValue(ct.d)) {
+			errf("want time %v, got %v", ct.wanttime, timeValue(ct.d))
+		}
+		if ct.wantnil && *ct.d.(**int64) != nil {
+			errf("want nil, got %v", intPtrValue(ct.d))
+		}
+		if ct.wantptr != nil {
+			if *ct.d.(**int64) == nil {
+				errf("want pointer to %v, got nil", *ct.wantptr)
+			} else if *ct.wantptr != intPtrValue(ct.d) {
+				errf("want pointer to %v, got %v", *ct.wantptr, intPtrValue(ct.d))
+			}
+		}
+		if ifptr, ok := ct.d.(*interface{}); ok {
+			if !reflect.DeepEqual(ct.wantiface, scaniface) {
+				errf("want interface %#v, got %#v", ct.wantiface, scaniface)
+				continue
+			}
+			if srcBytes, ok := ct.s.([]byte); ok {
+				dstBytes := (*ifptr).([]byte)
+				if len(srcBytes) > 0 && &dstBytes[0] == &srcBytes[0] {
+					errf("copy into interface{} didn't copy []byte data")
+				}
+			}
+		}
+		if ct.wantusrdef != 0 && ct.wantusrdef != *ct.d.(*userDefined) {
+			errf("want userDefined %f, got %f", ct.wantusrdef, *ct.d.(*userDefined))
+		}
+		if len(ct.wantusrstr) != 0 && ct.wantusrstr != *ct.d.(*userDefinedString) {
+			errf("want userDefined %q, got %q", ct.wantusrstr, *ct.d.(*userDefinedString))
+		}
+	}
+}
+
+func TestNullString(t *testing.T) {
+	var ns NullString
+	convertAssign(&ns, []byte("foo"))
+	if !ns.Valid {
+		t.Errorf("expecting not null")
+	}
+	if ns.String != "foo" {
+		t.Errorf("expecting foo; got %q", ns.String)
+	}
+	convertAssign(&ns, nil)
+	if ns.Valid {
+		t.Errorf("expecting null on nil")
+	}
+	if ns.String != "" {
+		t.Errorf("expecting blank on nil; got %q", ns.String)
+	}
+}
+
+type valueConverterTest struct {
+	c       driver.ValueConverter
+	in, out interface{}
+	err     string
+}
+
+var valueConverterTests = []valueConverterTest{
+	{driver.DefaultParameterConverter, NullString{"hi", true}, "hi", ""},
+	{driver.DefaultParameterConverter, NullString{"", false}, nil, ""},
+}
+
+func TestValueConverters(t *testing.T) {
+	for i, tt := range valueConverterTests {
+		out, err := tt.c.ConvertValue(tt.in)
+		goterr := ""
+		if err != nil {
+			goterr = err.Error()
+		}
+		if goterr != tt.err {
+			t.Errorf("test %d: %T(%T(%v)) error = %q; want error = %q",
+				i, tt.c, tt.in, tt.in, goterr, tt.err)
+		}
+		if tt.err != "" {
+			continue
+		}
+		if !reflect.DeepEqual(out, tt.out) {
+			t.Errorf("test %d: %T(%T(%v)) = %v (%T); want %v (%T)",
+				i, tt.c, tt.in, tt.in, out, out, tt.out, tt.out)
+		}
+	}
+}
+
+// Tests that assigning to RawBytes doesn't allocate (and also works).
+func TestRawBytesAllocs(t *testing.T) {
+	var tests = []struct {
+		name string
+		in   interface{}
+		want string
+	}{
+		{"uint64", uint64(12345678), "12345678"},
+		{"uint32", uint32(1234), "1234"},
+		{"uint16", uint16(12), "12"},
+		{"uint8", uint8(1), "1"},
+		{"uint", uint(123), "123"},
+		{"int", int(123), "123"},
+		{"int8", int8(1), "1"},
+		{"int16", int16(12), "12"},
+		{"int32", int32(1234), "1234"},
+		{"int64", int64(12345678), "12345678"},
+		{"float32", float32(1.5), "1.5"},
+		{"float64", float64(64), "64"},
+		{"bool", false, "false"},
+		{"time", time.Unix(2, 5).UTC(), "1970-01-01T00:00:02.000000005Z"},
+	}
+
+	buf := make(RawBytes, 10)
+	test := func(name string, in interface{}, want string) {
+		if err := convertAssign(&buf, in); err != nil {
+			t.Fatalf("%s: convertAssign = %v", name, err)
+		}
+		match := len(buf) == len(want)
+		if match {
+			for i, b := range buf {
+				if want[i] != b {
+					match = false
+					break
+				}
+			}
+		}
+		if !match {
+			t.Fatalf("%s: got %q (len %d); want %q (len %d)", name, buf, len(buf), want, len(want))
+		}
+	}
+
+	n := testing.AllocsPerRun(100, func() {
+		for _, tt := range tests {
+			test(tt.name, tt.in, tt.want)
+		}
+	})
+
+	// The numbers below are only valid for 64-bit interface word sizes,
+	// and gc. With 32-bit words there are more convT2E allocs, and
+	// with gccgo, only pointers currently go in interface data.
+	// So only care on amd64 gc for now.
+	measureAllocs := runtime.GOARCH == "amd64" && runtime.Compiler == "gc"
+
+	if n > 0.5 && measureAllocs {
+		t.Fatalf("allocs = %v; want 0", n)
+	}
+
+	// This one involves a convT2E allocation, string -> interface{}
+	n = testing.AllocsPerRun(100, func() {
+		test("string", "foo", "foo")
+	})
+	if n > 1.5 && measureAllocs {
+		t.Fatalf("allocs = %v; want max 1", n)
+	}
+}
+
+// https://golang.org/issues/13905
+func TestUserDefinedBytes(t *testing.T) {
+	type userDefinedBytes []byte
+	var u userDefinedBytes
+	v := []byte("foo")
+
+	convertAssign(&u, v)
+	if &u[0] == &v[0] {
+		t.Fatal("userDefinedBytes got potentially dirty driver memory")
+	}
+}
+
+type Valuer_V string
+
+func (v Valuer_V) Value() (driver.Value, error) {
+	return strings.ToUpper(string(v)), nil
+}
+
+type Valuer_P string
+
+func (p *Valuer_P) Value() (driver.Value, error) {
+	if p == nil {
+		return "nil-to-str", nil
+	}
+	return strings.ToUpper(string(*p)), nil
+}
+
+func TestDriverArgs(t *testing.T) {
+	var nilValuerVPtr *Valuer_V
+	var nilValuerPPtr *Valuer_P
+	var nilStrPtr *string
+	tests := []struct {
+		args []interface{}
+		want []driver.NamedValue
+	}{
+		0: {
+			args: []interface{}{Valuer_V("foo")},
+			want: []driver.NamedValue{
+				{
+					Ordinal: 1,
+					Value:   "FOO",
+				},
+			},
+		},
+		1: {
+			args: []interface{}{nilValuerVPtr},
+			want: []driver.NamedValue{
+				{
+					Ordinal: 1,
+					Value:   nil,
+				},
+			},
+		},
+		2: {
+			args: []interface{}{nilValuerPPtr},
+			want: []driver.NamedValue{
+				{
+					Ordinal: 1,
+					Value:   "nil-to-str",
+				},
+			},
+		},
+		3: {
+			args: []interface{}{"plain-str"},
+			want: []driver.NamedValue{
+				{
+					Ordinal: 1,
+					Value:   "plain-str",
+				},
+			},
+		},
+		4: {
+			args: []interface{}{nilStrPtr},
+			want: []driver.NamedValue{
+				{
+					Ordinal: 1,
+					Value:   nil,
+				},
+			},
+		},
+	}
+	for i, tt := range tests {
+		ds := &driverStmt{Locker: &sync.Mutex{}, si: stubDriverStmt{nil}}
+		got, err := driverArgsConnLocked(nil, ds, tt.args)
+		if err != nil {
+			t.Errorf("test[%d]: %v", i, err)
+			continue
+		}
+		if !reflect.DeepEqual(got, tt.want) {
+			t.Errorf("test[%d]: got %v, want %v", i, got, tt.want)
+		}
+	}
+}
+
+type dec struct {
+	form        byte
+	neg         bool
+	coefficient [16]byte
+	exponent    int32
+}
+
+func (d dec) Decompose(buf []byte) (form byte, negative bool, coefficient []byte, exponent int32) {
+	coef := make([]byte, 16)
+	copy(coef, d.coefficient[:])
+	return d.form, d.neg, coef, d.exponent
+}
+
+func (d *dec) Compose(form byte, negative bool, coefficient []byte, exponent int32) error {
+	switch form {
+	default:
+		return fmt.Errorf("unknown form %d", form)
+	case 1, 2:
+		d.form = form
+		d.neg = negative
+		return nil
+	case 0:
+	}
+	d.form = form
+	d.neg = negative
+	d.exponent = exponent
+
+	// This isn't strictly correct, as the extra bytes could be all zero,
+	// ignore this for this test.
+	if len(coefficient) > 16 {
+		return fmt.Errorf("coefficient too large")
+	}
+	copy(d.coefficient[:], coefficient)
+
+	return nil
+}
+
+type decFinite struct {
+	neg         bool
+	coefficient [16]byte
+	exponent    int32
+}
+
+func (d decFinite) Decompose(buf []byte) (form byte, negative bool, coefficient []byte, exponent int32) {
+	coef := make([]byte, 16)
+	copy(coef, d.coefficient[:])
+	return 0, d.neg, coef, d.exponent
+}
+
+func (d *decFinite) Compose(form byte, negative bool, coefficient []byte, exponent int32) error {
+	switch form {
+	default:
+		return fmt.Errorf("unknown form %d", form)
+	case 1, 2:
+		return fmt.Errorf("unsupported form %d", form)
+	case 0:
+	}
+	d.neg = negative
+	d.exponent = exponent
+
+	// This isn't strictly correct, as the extra bytes could be all zero,
+	// ignore this for this test.
+	if len(coefficient) > 16 {
+		return fmt.Errorf("coefficient too large")
+	}
+	copy(d.coefficient[:], coefficient)
+
+	return nil
+}
+
+func TestDecimal(t *testing.T) {
+	list := []struct {
+		name string
+		in   decimalDecompose
+		out  dec
+		err  bool
+	}{
+		{name: "same", in: dec{exponent: -6}, out: dec{exponent: -6}},
+
+		// Ensure reflection is not used to assign the value by using different types.
+		{name: "diff", in: decFinite{exponent: -6}, out: dec{exponent: -6}},
+
+		{name: "bad-form", in: dec{form: 200}, err: true},
+	}
+	for _, item := range list {
+		t.Run(item.name, func(t *testing.T) {
+			out := dec{}
+			err := convertAssign(&out, item.in)
+			if item.err {
+				if err == nil {
+					t.Fatalf("unexpected nil error")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			if !reflect.DeepEqual(out, item.out) {
+				t.Fatalf("got %#v want %#v", out, item.out)
+			}
+		})
+	}
+}
diff --git a/src/database/sql/ctxutil.go b/src/database/sql/ctxutil.go
new file mode 100644
index 0000000..4dbe6af
--- /dev/null
+++ b/src/database/sql/ctxutil.go
@@ -0,0 +1,146 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sql
+
+import (
+	"context"
+	"database/sql/driver"
+	"errors"
+)
+
+func ctxDriverPrepare(ctx context.Context, ci driver.Conn, query string) (driver.Stmt, error) {
+	if ciCtx, is := ci.(driver.ConnPrepareContext); is {
+		return ciCtx.PrepareContext(ctx, query)
+	}
+	si, err := ci.Prepare(query)
+	if err == nil {
+		select {
+		default:
+		case <-ctx.Done():
+			si.Close()
+			return nil, ctx.Err()
+		}
+	}
+	return si, err
+}
+
+func ctxDriverExec(ctx context.Context, execerCtx driver.ExecerContext, execer driver.Execer, query string, nvdargs []driver.NamedValue) (driver.Result, error) {
+	if execerCtx != nil {
+		return execerCtx.ExecContext(ctx, query, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
+	}
+
+	select {
+	default:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+	return execer.Exec(query, dargs)
+}
+
+func ctxDriverQuery(ctx context.Context, queryerCtx driver.QueryerContext, queryer driver.Queryer, query string, nvdargs []driver.NamedValue) (driver.Rows, error) {
+	if queryerCtx != nil {
+		return queryerCtx.QueryContext(ctx, query, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
+	}
+
+	select {
+	default:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+	return queryer.Query(query, dargs)
+}
+
+func ctxDriverStmtExec(ctx context.Context, si driver.Stmt, nvdargs []driver.NamedValue) (driver.Result, error) {
+	if siCtx, is := si.(driver.StmtExecContext); is {
+		return siCtx.ExecContext(ctx, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
+	}
+
+	select {
+	default:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+	return si.Exec(dargs)
+}
+
+func ctxDriverStmtQuery(ctx context.Context, si driver.Stmt, nvdargs []driver.NamedValue) (driver.Rows, error) {
+	if siCtx, is := si.(driver.StmtQueryContext); is {
+		return siCtx.QueryContext(ctx, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
+	}
+
+	select {
+	default:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+	return si.Query(dargs)
+}
+
+func ctxDriverBegin(ctx context.Context, opts *TxOptions, ci driver.Conn) (driver.Tx, error) {
+	if ciCtx, is := ci.(driver.ConnBeginTx); is {
+		dopts := driver.TxOptions{}
+		if opts != nil {
+			dopts.Isolation = driver.IsolationLevel(opts.Isolation)
+			dopts.ReadOnly = opts.ReadOnly
+		}
+		return ciCtx.BeginTx(ctx, dopts)
+	}
+
+	if opts != nil {
+		// Check the transaction level. If the transaction level is non-default
+		// then return an error here as the BeginTx driver value is not supported.
+		if opts.Isolation != LevelDefault {
+			return nil, errors.New("sql: driver does not support non-default isolation level")
+		}
+
+		// If a read-only transaction is requested return an error as the
+		// BeginTx driver value is not supported.
+		if opts.ReadOnly {
+			return nil, errors.New("sql: driver does not support read-only transactions")
+		}
+	}
+
+	if ctx.Done() == nil {
+		return ci.Begin()
+	}
+
+	txi, err := ci.Begin()
+	if err == nil {
+		select {
+		default:
+		case <-ctx.Done():
+			txi.Rollback()
+			return nil, ctx.Err()
+		}
+	}
+	return txi, err
+}
+
+func namedValueToValue(named []driver.NamedValue) ([]driver.Value, error) {
+	dargs := make([]driver.Value, len(named))
+	for n, param := range named {
+		if len(param.Name) > 0 {
+			return nil, errors.New("sql: driver does not support the use of Named Parameters")
+		}
+		dargs[n] = param.Value
+	}
+	return dargs, nil
+}
diff --git a/src/database/sql/doc.txt b/src/database/sql/doc.txt
new file mode 100644
index 0000000..1341b57
--- /dev/null
+++ b/src/database/sql/doc.txt
@@ -0,0 +1,46 @@
+Goals of the sql and sql/driver packages:
+
+* Provide a generic database API for a variety of SQL or SQL-like
+  databases.  There currently exist Go libraries for SQLite, MySQL,
+  and Postgres, but all with a very different feel, and often
+  a non-Go-like feel.
+
+* Feel like Go.
+
+* Care mostly about the common cases. Common SQL should be portable.
+  SQL edge cases or db-specific extensions can be detected and
+  conditionally used by the application.  It is a non-goal to care
+  about every particular db's extension or quirk.
+
+* Separate out the basic implementation of a database driver
+  (implementing the sql/driver interfaces) vs the implementation
+  of all the user-level types and convenience methods.
+  In a nutshell:
+
+  User Code ---> sql package (concrete types) ---> sql/driver (interfaces)
+  Database Driver -> sql (to register) + sql/driver (implement interfaces)
+
+* Make type casting/conversions consistent between all drivers. To
+  achieve this, most of the conversions are done in the sql package,
+  not in each driver. The drivers then only have to deal with a
+  smaller set of types.
+
+* Be flexible with type conversions, but be paranoid about silent
+  truncation or other loss of precision.
+
+* Handle concurrency well.  Users shouldn't need to care about the
+  database's per-connection thread safety issues (or lack thereof),
+  and shouldn't have to maintain their own free pools of connections.
+  The 'sql' package should deal with that bookkeeping as needed.  Given
+  an *sql.DB, it should be possible to share that instance between
+  multiple goroutines, without any extra synchronization.
+
+* Push complexity, where necessary, down into the sql+driver packages,
+  rather than exposing it to users. Said otherwise, the sql package
+  should expose an ideal database that's not finnicky about how it's
+  accessed, even if that's not true.
+
+* Provide optional interfaces in sql/driver for drivers to implement
+  for special cases or fastpaths.  But the only party that knows about
+  those is the sql package.  To user code, some stuff just might start
+  working or start working slightly faster.
diff --git a/src/database/sql/driver/driver.go b/src/database/sql/driver/driver.go
new file mode 100644
index 0000000..5bbcf20
--- /dev/null
+++ b/src/database/sql/driver/driver.go
@@ -0,0 +1,544 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package driver defines interfaces to be implemented by database
+// drivers as used by package sql.
+//
+// Most code should use package sql.
+//
+// The driver interface has evolved over time. Drivers should implement
+// Connector and DriverContext interfaces.
+// The Connector.Connect and Driver.Open methods should never return ErrBadConn.
+// ErrBadConn should only be returned from Validator, SessionResetter, or
+// a query method if the connection is already in an invalid (e.g. closed) state.
+//
+// All Conn implementations should implement the following interfaces:
+// Pinger, SessionResetter, and Validator.
+//
+// If named parameters or context are supported, the driver's Conn should implement:
+// ExecerContext, QueryerContext, ConnPrepareContext, and ConnBeginTx.
+//
+// To support custom data types, implement NamedValueChecker. NamedValueChecker
+// also allows queries to accept per-query options as a parameter by returning
+// ErrRemoveArgument from CheckNamedValue.
+//
+// If multiple result sets are supported, Rows should implement RowsNextResultSet.
+// If the driver knows how to describe the types present in the returned result
+// it should implement the following interfaces: RowsColumnTypeScanType,
+// RowsColumnTypeDatabaseTypeName, RowsColumnTypeLength, RowsColumnTypeNullable,
+// and RowsColumnTypePrecisionScale. A given row value may also return a Rows
+// type, which may represent a database cursor value.
+//
+// Before a connection is returned to the connection pool after use, IsValid is
+// called if implemented. Before a connection is reused for another query,
+// ResetSession is called if implemented. If a connection is never returned to the
+// connection pool but immediately reused, then ResetSession is called prior to
+// reuse but IsValid is not called.
+package driver
+
+import (
+	"context"
+	"errors"
+	"reflect"
+)
+
+// Value is a value that drivers must be able to handle.
+// It is either nil, a type handled by a database driver's NamedValueChecker
+// interface, or an instance of one of these types:
+//
+//   int64
+//   float64
+//   bool
+//   []byte
+//   string
+//   time.Time
+//
+// If the driver supports cursors, a returned Value may also implement the Rows interface
+// in this package. This is used, for example, when a user selects a cursor
+// such as "select cursor(select * from my_table) from dual". If the Rows
+// from the select is closed, the cursor Rows will also be closed.
+type Value interface{}
+
+// NamedValue holds both the value name and value.
+type NamedValue struct {
+	// If the Name is not empty it should be used for the parameter identifier and
+	// not the ordinal position.
+	//
+	// Name will not have a symbol prefix.
+	Name string
+
+	// Ordinal position of the parameter starting from one and is always set.
+	Ordinal int
+
+	// Value is the parameter value.
+	Value Value
+}
+
+// Driver is the interface that must be implemented by a database
+// driver.
+//
+// Database drivers may implement DriverContext for access
+// to contexts and to parse the name only once for a pool of connections,
+// instead of once per connection.
+type Driver interface {
+	// Open returns a new connection to the database.
+	// The name is a string in a driver-specific format.
+	//
+	// Open may return a cached connection (one previously
+	// closed), but doing so is unnecessary; the sql package
+	// maintains a pool of idle connections for efficient re-use.
+	//
+	// The returned connection is only used by one goroutine at a
+	// time.
+	Open(name string) (Conn, error)
+}
+
+// If a Driver implements DriverContext, then sql.DB will call
+// OpenConnector to obtain a Connector and then invoke
+// that Connector's Connect method to obtain each needed connection,
+// instead of invoking the Driver's Open method for each connection.
+// The two-step sequence allows drivers to parse the name just once
+// and also provides access to per-Conn contexts.
+type DriverContext interface {
+	// OpenConnector must parse the name in the same format that Driver.Open
+	// parses the name parameter.
+	OpenConnector(name string) (Connector, error)
+}
+
+// A Connector represents a driver in a fixed configuration
+// and can create any number of equivalent Conns for use
+// by multiple goroutines.
+//
+// A Connector can be passed to sql.OpenDB, to allow drivers
+// to implement their own sql.DB constructors, or returned by
+// DriverContext's OpenConnector method, to allow drivers
+// access to context and to avoid repeated parsing of driver
+// configuration.
+type Connector interface {
+	// Connect returns a connection to the database.
+	// Connect may return a cached connection (one previously
+	// closed), but doing so is unnecessary; the sql package
+	// maintains a pool of idle connections for efficient re-use.
+	//
+	// The provided context.Context is for dialing purposes only
+	// (see net.DialContext) and should not be stored or used for
+	// other purposes. A default timeout should still be used
+	// when dialing as a connection pool may call Connect
+	// asynchronously to any query.
+	//
+	// The returned connection is only used by one goroutine at a
+	// time.
+	Connect(context.Context) (Conn, error)
+
+	// Driver returns the underlying Driver of the Connector,
+	// mainly to maintain compatibility with the Driver method
+	// on sql.DB.
+	Driver() Driver
+}
+
+// ErrSkip may be returned by some optional interfaces' methods to
+// indicate at runtime that the fast path is unavailable and the sql
+// package should continue as if the optional interface was not
+// implemented. ErrSkip is only supported where explicitly
+// documented.
+var ErrSkip = errors.New("driver: skip fast-path; continue as if unimplemented")
+
+// ErrBadConn should be returned by a driver to signal to the sql
+// package that a driver.Conn is in a bad state (such as the server
+// having earlier closed the connection) and the sql package should
+// retry on a new connection.
+//
+// To prevent duplicate operations, ErrBadConn should NOT be returned
+// if there's a possibility that the database server might have
+// performed the operation. Even if the server sends back an error,
+// you shouldn't return ErrBadConn.
+var ErrBadConn = errors.New("driver: bad connection")
+
+// Pinger is an optional interface that may be implemented by a Conn.
+//
+// If a Conn does not implement Pinger, the sql package's DB.Ping and
+// DB.PingContext will check if there is at least one Conn available.
+//
+// If Conn.Ping returns ErrBadConn, DB.Ping and DB.PingContext will remove
+// the Conn from pool.
+type Pinger interface {
+	Ping(ctx context.Context) error
+}
+
+// Execer is an optional interface that may be implemented by a Conn.
+//
+// If a Conn implements neither ExecerContext nor Execer,
+// the sql package's DB.Exec will first prepare a query, execute the statement,
+// and then close the statement.
+//
+// Exec may return ErrSkip.
+//
+// Deprecated: Drivers should implement ExecerContext instead.
+type Execer interface {
+	Exec(query string, args []Value) (Result, error)
+}
+
+// ExecerContext is an optional interface that may be implemented by a Conn.
+//
+// If a Conn does not implement ExecerContext, the sql package's DB.Exec
+// will fall back to Execer; if the Conn does not implement Execer either,
+// DB.Exec will first prepare a query, execute the statement, and then
+// close the statement.
+//
+// ExecerContext may return ErrSkip.
+//
+// ExecerContext must honor the context timeout and return when the context is canceled.
+type ExecerContext interface {
+	ExecContext(ctx context.Context, query string, args []NamedValue) (Result, error)
+}
+
+// Queryer is an optional interface that may be implemented by a Conn.
+//
+// If a Conn implements neither QueryerContext nor Queryer,
+// the sql package's DB.Query will first prepare a query, execute the statement,
+// and then close the statement.
+//
+// Query may return ErrSkip.
+//
+// Deprecated: Drivers should implement QueryerContext instead.
+type Queryer interface {
+	Query(query string, args []Value) (Rows, error)
+}
+
+// QueryerContext is an optional interface that may be implemented by a Conn.
+//
+// If a Conn does not implement QueryerContext, the sql package's DB.Query
+// will fall back to Queryer; if the Conn does not implement Queryer either,
+// DB.Query will first prepare a query, execute the statement, and then
+// close the statement.
+//
+// QueryerContext may return ErrSkip.
+//
+// QueryerContext must honor the context timeout and return when the context is canceled.
+type QueryerContext interface {
+	QueryContext(ctx context.Context, query string, args []NamedValue) (Rows, error)
+}
+
+// Conn is a connection to a database. It is not used concurrently
+// by multiple goroutines.
+//
+// Conn is assumed to be stateful.
+type Conn interface {
+	// Prepare returns a prepared statement, bound to this connection.
+	Prepare(query string) (Stmt, error)
+
+	// Close invalidates and potentially stops any current
+	// prepared statements and transactions, marking this
+	// connection as no longer in use.
+	//
+	// Because the sql package maintains a free pool of
+	// connections and only calls Close when there's a surplus of
+	// idle connections, it shouldn't be necessary for drivers to
+	// do their own connection caching.
+	//
+	// Drivers must ensure all network calls made by Close
+	// do not block indefinitely (e.g. apply a timeout).
+	Close() error
+
+	// Begin starts and returns a new transaction.
+	//
+	// Deprecated: Drivers should implement ConnBeginTx instead (or additionally).
+	Begin() (Tx, error)
+}
+
+// ConnPrepareContext enhances the Conn interface with context.
+type ConnPrepareContext interface {
+	// PrepareContext returns a prepared statement, bound to this connection.
+	// context is for the preparation of the statement,
+	// it must not store the context within the statement itself.
+	PrepareContext(ctx context.Context, query string) (Stmt, error)
+}
+
+// IsolationLevel is the transaction isolation level stored in TxOptions.
+//
+// This type should be considered identical to sql.IsolationLevel along
+// with any values defined on it.
+type IsolationLevel int
+
+// TxOptions holds the transaction options.
+//
+// This type should be considered identical to sql.TxOptions.
+type TxOptions struct {
+	Isolation IsolationLevel
+	ReadOnly  bool
+}
+
+// ConnBeginTx enhances the Conn interface with context and TxOptions.
+type ConnBeginTx interface {
+	// BeginTx starts and returns a new transaction.
+	// If the context is canceled by the user the sql package will
+	// call Tx.Rollback before discarding and closing the connection.
+	//
+	// This must check opts.Isolation to determine if there is a set
+	// isolation level. If the driver does not support a non-default
+	// level and one is set or if there is a non-default isolation level
+	// that is not supported, an error must be returned.
+	//
+	// This must also check opts.ReadOnly to determine if the read-only
+	// value is true to either set the read-only transaction property if supported
+	// or return an error if it is not supported.
+	BeginTx(ctx context.Context, opts TxOptions) (Tx, error)
+}
+
+// SessionResetter may be implemented by Conn to allow drivers to reset the
+// session state associated with the connection and to signal a bad connection.
+type SessionResetter interface {
+	// ResetSession is called prior to executing a query on the connection
+	// if the connection has been used before. If the driver returns ErrBadConn
+	// the connection is discarded.
+	ResetSession(ctx context.Context) error
+}
+
+// Validator may be implemented by Conn to allow drivers to
+// signal if a connection is valid or if it should be discarded.
+//
+// If implemented, drivers may return the underlying error from queries,
+// even if the connection should be discarded by the connection pool.
+type Validator interface {
+	// IsValid is called prior to placing the connection into the
+	// connection pool. The connection will be discarded if false is returned.
+	IsValid() bool
+}
+
+// Result is the result of a query execution.
+type Result interface {
+	// LastInsertId returns the database's auto-generated ID
+	// after, for example, an INSERT into a table with primary
+	// key.
+	LastInsertId() (int64, error)
+
+	// RowsAffected returns the number of rows affected by the
+	// query.
+	RowsAffected() (int64, error)
+}
+
+// Stmt is a prepared statement. It is bound to a Conn and not
+// used by multiple goroutines concurrently.
+type Stmt interface {
+	// Close closes the statement.
+	//
+	// As of Go 1.1, a Stmt will not be closed if it's in use
+	// by any queries.
+	//
+	// Drivers must ensure all network calls made by Close
+	// do not block indefinitely (e.g. apply a timeout).
+	Close() error
+
+	// NumInput returns the number of placeholder parameters.
+	//
+	// If NumInput returns >= 0, the sql package will sanity check
+	// argument counts from callers and return errors to the caller
+	// before the statement's Exec or Query methods are called.
+	//
+	// NumInput may also return -1, if the driver doesn't know
+	// its number of placeholders. In that case, the sql package
+	// will not sanity check Exec or Query argument counts.
+	NumInput() int
+
+	// Exec executes a query that doesn't return rows, such
+	// as an INSERT or UPDATE.
+	//
+	// Deprecated: Drivers should implement StmtExecContext instead (or additionally).
+	Exec(args []Value) (Result, error)
+
+	// Query executes a query that may return rows, such as a
+	// SELECT.
+	//
+	// Deprecated: Drivers should implement StmtQueryContext instead (or additionally).
+	Query(args []Value) (Rows, error)
+}
+
+// StmtExecContext enhances the Stmt interface by providing Exec with context.
+type StmtExecContext interface {
+	// ExecContext executes a query that doesn't return rows, such
+	// as an INSERT or UPDATE.
+	//
+	// ExecContext must honor the context timeout and return when it is canceled.
+	ExecContext(ctx context.Context, args []NamedValue) (Result, error)
+}
+
+// StmtQueryContext enhances the Stmt interface by providing Query with context.
+type StmtQueryContext interface {
+	// QueryContext executes a query that may return rows, such as a
+	// SELECT.
+	//
+	// QueryContext must honor the context timeout and return when it is canceled.
+	QueryContext(ctx context.Context, args []NamedValue) (Rows, error)
+}
+
+// ErrRemoveArgument may be returned from NamedValueChecker to instruct the
+// sql package to not pass the argument to the driver query interface.
+// Return when accepting query specific options or structures that aren't
+// SQL query arguments.
+var ErrRemoveArgument = errors.New("driver: remove argument from query")
+
+// NamedValueChecker may be optionally implemented by Conn or Stmt. It provides
+// the driver more control to handle Go and database types beyond the default
+// Values types allowed.
+//
+// The sql package checks for value checkers in the following order,
+// stopping at the first found match: Stmt.NamedValueChecker, Conn.NamedValueChecker,
+// Stmt.ColumnConverter, DefaultParameterConverter.
+//
+// If CheckNamedValue returns ErrRemoveArgument, the NamedValue will not be included in
+// the final query arguments. This may be used to pass special options to
+// the query itself.
+//
+// If ErrSkip is returned the column converter error checking
+// path is used for the argument. Drivers may wish to return ErrSkip after
+// they have exhausted their own special cases.
+type NamedValueChecker interface {
+	// CheckNamedValue is called before passing arguments to the driver
+	// and is called in place of any ColumnConverter. CheckNamedValue must do type
+	// validation and conversion as appropriate for the driver.
+	CheckNamedValue(*NamedValue) error
+}
+
+// ColumnConverter may be optionally implemented by Stmt if the
+// statement is aware of its own columns' types and can convert from
+// any type to a driver Value.
+//
+// Deprecated: Drivers should implement NamedValueChecker.
+type ColumnConverter interface {
+	// ColumnConverter returns a ValueConverter for the provided
+	// column index. If the type of a specific column isn't known
+	// or shouldn't be handled specially, DefaultValueConverter
+	// can be returned.
+	ColumnConverter(idx int) ValueConverter
+}
+
+// Rows is an iterator over an executed query's results.
+type Rows interface {
+	// Columns returns the names of the columns. The number of
+	// columns of the result is inferred from the length of the
+	// slice. If a particular column name isn't known, an empty
+	// string should be returned for that entry.
+	Columns() []string
+
+	// Close closes the rows iterator.
+	Close() error
+
+	// Next is called to populate the next row of data into
+	// the provided slice. The provided slice will be the same
+	// size as the Columns() are wide.
+	//
+	// Next should return io.EOF when there are no more rows.
+	//
+	// The dest should not be written to outside of Next. Care
+	// should be taken when closing Rows not to modify
+	// a buffer held in dest.
+	Next(dest []Value) error
+}
+
+// RowsNextResultSet extends the Rows interface by providing a way to signal
+// the driver to advance to the next result set.
+type RowsNextResultSet interface {
+	Rows
+
+	// HasNextResultSet is called at the end of the current result set and
+	// reports whether there is another result set after the current one.
+	HasNextResultSet() bool
+
+	// NextResultSet advances the driver to the next result set even
+	// if there are remaining rows in the current result set.
+	//
+	// NextResultSet should return io.EOF when there are no more result sets.
+	NextResultSet() error
+}
+
+// RowsColumnTypeScanType may be implemented by Rows. It should return
+// the value type that can be used to scan types into. For example, the database
+// column type "bigint" this should return "reflect.TypeOf(int64(0))".
+type RowsColumnTypeScanType interface {
+	Rows
+	ColumnTypeScanType(index int) reflect.Type
+}
+
+// RowsColumnTypeDatabaseTypeName may be implemented by Rows. It should return the
+// database system type name without the length. Type names should be uppercase.
+// Examples of returned types: "VARCHAR", "NVARCHAR", "VARCHAR2", "CHAR", "TEXT",
+// "DECIMAL", "SMALLINT", "INT", "BIGINT", "BOOL", "[]BIGINT", "JSONB", "XML",
+// "TIMESTAMP".
+type RowsColumnTypeDatabaseTypeName interface {
+	Rows
+	ColumnTypeDatabaseTypeName(index int) string
+}
+
+// RowsColumnTypeLength may be implemented by Rows. It should return the length
+// of the column type if the column is a variable length type. If the column is
+// not a variable length type ok should return false.
+// If length is not limited other than system limits, it should return math.MaxInt64.
+// The following are examples of returned values for various types:
+//   TEXT          (math.MaxInt64, true)
+//   varchar(10)   (10, true)
+//   nvarchar(10)  (10, true)
+//   decimal       (0, false)
+//   int           (0, false)
+//   bytea(30)     (30, true)
+type RowsColumnTypeLength interface {
+	Rows
+	ColumnTypeLength(index int) (length int64, ok bool)
+}
+
+// RowsColumnTypeNullable may be implemented by Rows. The nullable value should
+// be true if it is known the column may be null, or false if the column is known
+// to be not nullable.
+// If the column nullability is unknown, ok should be false.
+type RowsColumnTypeNullable interface {
+	Rows
+	ColumnTypeNullable(index int) (nullable, ok bool)
+}
+
+// RowsColumnTypePrecisionScale may be implemented by Rows. It should return
+// the precision and scale for decimal types. If not applicable, ok should be false.
+// The following are examples of returned values for various types:
+//   decimal(38, 4)    (38, 4, true)
+//   int               (0, 0, false)
+//   decimal           (math.MaxInt64, math.MaxInt64, true)
+type RowsColumnTypePrecisionScale interface {
+	Rows
+	ColumnTypePrecisionScale(index int) (precision, scale int64, ok bool)
+}
+
+// Tx is a transaction.
+type Tx interface {
+	Commit() error
+	Rollback() error
+}
+
+// RowsAffected implements Result for an INSERT or UPDATE operation
+// which mutates a number of rows.
+type RowsAffected int64
+
+var _ Result = RowsAffected(0)
+
+func (RowsAffected) LastInsertId() (int64, error) {
+	return 0, errors.New("LastInsertId is not supported by this driver")
+}
+
+func (v RowsAffected) RowsAffected() (int64, error) {
+	return int64(v), nil
+}
+
+// ResultNoRows is a pre-defined Result for drivers to return when a DDL
+// command (such as a CREATE TABLE) succeeds. It returns an error for both
+// LastInsertId and RowsAffected.
+var ResultNoRows noRows
+
+type noRows struct{}
+
+var _ Result = noRows{}
+
+func (noRows) LastInsertId() (int64, error) {
+	return 0, errors.New("no LastInsertId available after DDL statement")
+}
+
+func (noRows) RowsAffected() (int64, error) {
+	return 0, errors.New("no RowsAffected available after DDL statement")
+}
diff --git a/src/database/sql/driver/types.go b/src/database/sql/driver/types.go
new file mode 100644
index 0000000..24c3a45
--- /dev/null
+++ b/src/database/sql/driver/types.go
@@ -0,0 +1,297 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package driver
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"time"
+)
+
+// ValueConverter is the interface providing the ConvertValue method.
+//
+// Various implementations of ValueConverter are provided by the
+// driver package to provide consistent implementations of conversions
+// between drivers. The ValueConverters have several uses:
+//
+//  * converting from the Value types as provided by the sql package
+//    into a database table's specific column type and making sure it
+//    fits, such as making sure a particular int64 fits in a
+//    table's uint16 column.
+//
+//  * converting a value as given from the database into one of the
+//    driver Value types.
+//
+//  * by the sql package, for converting from a driver's Value type
+//    to a user's type in a scan.
+type ValueConverter interface {
+	// ConvertValue converts a value to a driver Value.
+	ConvertValue(v interface{}) (Value, error)
+}
+
+// Valuer is the interface providing the Value method.
+//
+// Types implementing Valuer interface are able to convert
+// themselves to a driver Value.
+type Valuer interface {
+	// Value returns a driver Value.
+	// Value must not panic.
+	Value() (Value, error)
+}
+
+// Bool is a ValueConverter that converts input values to bools.
+//
+// The conversion rules are:
+//  - booleans are returned unchanged
+//  - for integer types,
+//       1 is true
+//       0 is false,
+//       other integers are an error
+//  - for strings and []byte, same rules as strconv.ParseBool
+//  - all other types are an error
+var Bool boolType
+
+type boolType struct{}
+
+var _ ValueConverter = boolType{}
+
+func (boolType) String() string { return "Bool" }
+
+func (boolType) ConvertValue(src interface{}) (Value, error) {
+	switch s := src.(type) {
+	case bool:
+		return s, nil
+	case string:
+		b, err := strconv.ParseBool(s)
+		if err != nil {
+			return nil, fmt.Errorf("sql/driver: couldn't convert %q into type bool", s)
+		}
+		return b, nil
+	case []byte:
+		b, err := strconv.ParseBool(string(s))
+		if err != nil {
+			return nil, fmt.Errorf("sql/driver: couldn't convert %q into type bool", s)
+		}
+		return b, nil
+	}
+
+	sv := reflect.ValueOf(src)
+	switch sv.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		iv := sv.Int()
+		if iv == 1 || iv == 0 {
+			return iv == 1, nil
+		}
+		return nil, fmt.Errorf("sql/driver: couldn't convert %d into type bool", iv)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		uv := sv.Uint()
+		if uv == 1 || uv == 0 {
+			return uv == 1, nil
+		}
+		return nil, fmt.Errorf("sql/driver: couldn't convert %d into type bool", uv)
+	}
+
+	return nil, fmt.Errorf("sql/driver: couldn't convert %v (%T) into type bool", src, src)
+}
+
+// Int32 is a ValueConverter that converts input values to int64,
+// respecting the limits of an int32 value.
+var Int32 int32Type
+
+type int32Type struct{}
+
+var _ ValueConverter = int32Type{}
+
+func (int32Type) ConvertValue(v interface{}) (Value, error) {
+	rv := reflect.ValueOf(v)
+	switch rv.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		i64 := rv.Int()
+		if i64 > (1<<31)-1 || i64 < -(1<<31) {
+			return nil, fmt.Errorf("sql/driver: value %d overflows int32", v)
+		}
+		return i64, nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		u64 := rv.Uint()
+		if u64 > (1<<31)-1 {
+			return nil, fmt.Errorf("sql/driver: value %d overflows int32", v)
+		}
+		return int64(u64), nil
+	case reflect.String:
+		i, err := strconv.Atoi(rv.String())
+		if err != nil {
+			return nil, fmt.Errorf("sql/driver: value %q can't be converted to int32", v)
+		}
+		return int64(i), nil
+	}
+	return nil, fmt.Errorf("sql/driver: unsupported value %v (type %T) converting to int32", v, v)
+}
+
+// String is a ValueConverter that converts its input to a string.
+// If the value is already a string or []byte, it's unchanged.
+// If the value is of another type, conversion to string is done
+// with fmt.Sprintf("%v", v).
+var String stringType
+
+type stringType struct{}
+
+func (stringType) ConvertValue(v interface{}) (Value, error) {
+	switch v.(type) {
+	case string, []byte:
+		return v, nil
+	}
+	return fmt.Sprintf("%v", v), nil
+}
+
+// Null is a type that implements ValueConverter by allowing nil
+// values but otherwise delegating to another ValueConverter.
+type Null struct {
+	Converter ValueConverter
+}
+
+func (n Null) ConvertValue(v interface{}) (Value, error) {
+	if v == nil {
+		return nil, nil
+	}
+	return n.Converter.ConvertValue(v)
+}
+
+// NotNull is a type that implements ValueConverter by disallowing nil
+// values but otherwise delegating to another ValueConverter.
+type NotNull struct {
+	Converter ValueConverter
+}
+
+func (n NotNull) ConvertValue(v interface{}) (Value, error) {
+	if v == nil {
+		return nil, fmt.Errorf("nil value not allowed")
+	}
+	return n.Converter.ConvertValue(v)
+}
+
+// IsValue reports whether v is a valid Value parameter type.
+func IsValue(v interface{}) bool {
+	if v == nil {
+		return true
+	}
+	switch v.(type) {
+	case []byte, bool, float64, int64, string, time.Time:
+		return true
+	case decimalDecompose:
+		return true
+	}
+	return false
+}
+
+// IsScanValue is equivalent to IsValue.
+// It exists for compatibility.
+func IsScanValue(v interface{}) bool {
+	return IsValue(v)
+}
+
+// DefaultParameterConverter is the default implementation of
+// ValueConverter that's used when a Stmt doesn't implement
+// ColumnConverter.
+//
+// DefaultParameterConverter returns its argument directly if
+// IsValue(arg). Otherwise, if the argument implements Valuer, its
+// Value method is used to return a Value. As a fallback, the provided
+// argument's underlying type is used to convert it to a Value:
+// underlying integer types are converted to int64, floats to float64,
+// bool, string, and []byte to themselves. If the argument is a nil
+// pointer, ConvertValue returns a nil Value. If the argument is a
+// non-nil pointer, it is dereferenced and ConvertValue is called
+// recursively. Other types are an error.
+var DefaultParameterConverter defaultConverter
+
+type defaultConverter struct{}
+
+var _ ValueConverter = defaultConverter{}
+
+var valuerReflectType = reflect.TypeOf((*Valuer)(nil)).Elem()
+
+// callValuerValue returns vr.Value(), with one exception:
+// If vr.Value is an auto-generated method on a pointer type and the
+// pointer is nil, it would panic at runtime in the panicwrap
+// method. Treat it like nil instead.
+// Issue 8415.
+//
+// This is so people can implement driver.Value on value types and
+// still use nil pointers to those types to mean nil/NULL, just like
+// string/*string.
+//
+// This function is mirrored in the database/sql package.
+func callValuerValue(vr Valuer) (v Value, err error) {
+	if rv := reflect.ValueOf(vr); rv.Kind() == reflect.Ptr &&
+		rv.IsNil() &&
+		rv.Type().Elem().Implements(valuerReflectType) {
+		return nil, nil
+	}
+	return vr.Value()
+}
+
+func (defaultConverter) ConvertValue(v interface{}) (Value, error) {
+	if IsValue(v) {
+		return v, nil
+	}
+
+	switch vr := v.(type) {
+	case Valuer:
+		sv, err := callValuerValue(vr)
+		if err != nil {
+			return nil, err
+		}
+		if !IsValue(sv) {
+			return nil, fmt.Errorf("non-Value type %T returned from Value", sv)
+		}
+		return sv, nil
+
+	// For now, continue to prefer the Valuer interface over the decimal decompose interface.
+	case decimalDecompose:
+		return vr, nil
+	}
+
+	rv := reflect.ValueOf(v)
+	switch rv.Kind() {
+	case reflect.Ptr:
+		// indirect pointers
+		if rv.IsNil() {
+			return nil, nil
+		} else {
+			return defaultConverter{}.ConvertValue(rv.Elem().Interface())
+		}
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return rv.Int(), nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32:
+		return int64(rv.Uint()), nil
+	case reflect.Uint64:
+		u64 := rv.Uint()
+		if u64 >= 1<<63 {
+			return nil, fmt.Errorf("uint64 values with high bit set are not supported")
+		}
+		return int64(u64), nil
+	case reflect.Float32, reflect.Float64:
+		return rv.Float(), nil
+	case reflect.Bool:
+		return rv.Bool(), nil
+	case reflect.Slice:
+		ek := rv.Type().Elem().Kind()
+		if ek == reflect.Uint8 {
+			return rv.Bytes(), nil
+		}
+		return nil, fmt.Errorf("unsupported type %T, a slice of %s", v, ek)
+	case reflect.String:
+		return rv.String(), nil
+	}
+	return nil, fmt.Errorf("unsupported type %T, a %s", v, rv.Kind())
+}
+
+type decimalDecompose interface {
+	// Decompose returns the internal decimal state into parts.
+	// If the provided buf has sufficient capacity, buf may be returned as the coefficient with
+	// the value set and length set as appropriate.
+	Decompose(buf []byte) (form byte, negative bool, coefficient []byte, exponent int32)
+}
diff --git a/src/database/sql/driver/types_test.go b/src/database/sql/driver/types_test.go
new file mode 100644
index 0000000..4c2996d
--- /dev/null
+++ b/src/database/sql/driver/types_test.go
@@ -0,0 +1,95 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package driver
+
+import (
+	"reflect"
+	"testing"
+	"time"
+)
+
+type valueConverterTest struct {
+	c   ValueConverter
+	in  interface{}
+	out interface{}
+	err string
+}
+
+var now = time.Now()
+var answer int64 = 42
+
+type (
+	i  int64
+	f  float64
+	b  bool
+	bs []byte
+	s  string
+	t  time.Time
+	is []int
+)
+
+var valueConverterTests = []valueConverterTest{
+	{Bool, "true", true, ""},
+	{Bool, "True", true, ""},
+	{Bool, []byte("t"), true, ""},
+	{Bool, true, true, ""},
+	{Bool, "1", true, ""},
+	{Bool, 1, true, ""},
+	{Bool, int64(1), true, ""},
+	{Bool, uint16(1), true, ""},
+	{Bool, "false", false, ""},
+	{Bool, false, false, ""},
+	{Bool, "0", false, ""},
+	{Bool, 0, false, ""},
+	{Bool, int64(0), false, ""},
+	{Bool, uint16(0), false, ""},
+	{c: Bool, in: "foo", err: "sql/driver: couldn't convert \"foo\" into type bool"},
+	{c: Bool, in: 2, err: "sql/driver: couldn't convert 2 into type bool"},
+	{DefaultParameterConverter, now, now, ""},
+	{DefaultParameterConverter, (*int64)(nil), nil, ""},
+	{DefaultParameterConverter, &answer, answer, ""},
+	{DefaultParameterConverter, &now, now, ""},
+	{DefaultParameterConverter, i(9), int64(9), ""},
+	{DefaultParameterConverter, f(0.1), float64(0.1), ""},
+	{DefaultParameterConverter, b(true), true, ""},
+	{DefaultParameterConverter, bs{1}, []byte{1}, ""},
+	{DefaultParameterConverter, s("a"), "a", ""},
+	{DefaultParameterConverter, is{1}, nil, "unsupported type driver.is, a slice of int"},
+	{DefaultParameterConverter, dec{exponent: -6}, dec{exponent: -6}, ""},
+}
+
+func TestValueConverters(t *testing.T) {
+	for i, tt := range valueConverterTests {
+		out, err := tt.c.ConvertValue(tt.in)
+		goterr := ""
+		if err != nil {
+			goterr = err.Error()
+		}
+		if goterr != tt.err {
+			t.Errorf("test %d: %T(%T(%v)) error = %q; want error = %q",
+				i, tt.c, tt.in, tt.in, goterr, tt.err)
+		}
+		if tt.err != "" {
+			continue
+		}
+		if !reflect.DeepEqual(out, tt.out) {
+			t.Errorf("test %d: %T(%T(%v)) = %v (%T); want %v (%T)",
+				i, tt.c, tt.in, tt.in, out, out, tt.out, tt.out)
+		}
+	}
+}
+
+type dec struct {
+	form        byte
+	neg         bool
+	coefficient [16]byte
+	exponent    int32
+}
+
+func (d dec) Decompose(buf []byte) (form byte, negative bool, coefficient []byte, exponent int32) {
+	coef := make([]byte, 16)
+	copy(coef, d.coefficient[:])
+	return d.form, d.neg, coef, d.exponent
+}
diff --git a/src/database/sql/example_cli_test.go b/src/database/sql/example_cli_test.go
new file mode 100644
index 0000000..8c61d75
--- /dev/null
+++ b/src/database/sql/example_cli_test.go
@@ -0,0 +1,86 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sql_test
+
+import (
+	"context"
+	"database/sql"
+	"flag"
+	"log"
+	"os"
+	"os/signal"
+	"time"
+)
+
+var pool *sql.DB // Database connection pool.
+
+func Example_openDBCLI() {
+	id := flag.Int64("id", 0, "person ID to find")
+	dsn := flag.String("dsn", os.Getenv("DSN"), "connection data source name")
+	flag.Parse()
+
+	if len(*dsn) == 0 {
+		log.Fatal("missing dsn flag")
+	}
+	if *id == 0 {
+		log.Fatal("missing person ID")
+	}
+	var err error
+
+	// Opening a driver typically will not attempt to connect to the database.
+	pool, err = sql.Open("driver-name", *dsn)
+	if err != nil {
+		// This will not be a connection error, but a DSN parse error or
+		// another initialization error.
+		log.Fatal("unable to use data source name", err)
+	}
+	defer pool.Close()
+
+	pool.SetConnMaxLifetime(0)
+	pool.SetMaxIdleConns(3)
+	pool.SetMaxOpenConns(3)
+
+	ctx, stop := context.WithCancel(context.Background())
+	defer stop()
+
+	appSignal := make(chan os.Signal, 3)
+	signal.Notify(appSignal, os.Interrupt)
+
+	go func() {
+		select {
+		case <-appSignal:
+			stop()
+		}
+	}()
+
+	Ping(ctx)
+
+	Query(ctx, *id)
+}
+
+// Ping the database to verify DSN provided by the user is valid and the
+// server accessible. If the ping fails exit the program with an error.
+func Ping(ctx context.Context) {
+	ctx, cancel := context.WithTimeout(ctx, 1*time.Second)
+	defer cancel()
+
+	if err := pool.PingContext(ctx); err != nil {
+		log.Fatalf("unable to connect to database: %v", err)
+	}
+}
+
+// Query the database for the information requested and prints the results.
+// If the query fails exit the program with an error.
+func Query(ctx context.Context, id int64) {
+	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
+	defer cancel()
+
+	var name string
+	err := pool.QueryRowContext(ctx, "select p.name from people as p where p.id = :id;", sql.Named("id", id)).Scan(&name)
+	if err != nil {
+		log.Fatal("unable to execute search query", err)
+	}
+	log.Println("name=", name)
+}
diff --git a/src/database/sql/example_service_test.go b/src/database/sql/example_service_test.go
new file mode 100644
index 0000000..768307c
--- /dev/null
+++ b/src/database/sql/example_service_test.go
@@ -0,0 +1,158 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sql_test
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"time"
+)
+
+func Example_openDBService() {
+	// Opening a driver typically will not attempt to connect to the database.
+	db, err := sql.Open("driver-name", "database=test1")
+	if err != nil {
+		// This will not be a connection error, but a DSN parse error or
+		// another initialization error.
+		log.Fatal(err)
+	}
+	db.SetConnMaxLifetime(0)
+	db.SetMaxIdleConns(50)
+	db.SetMaxOpenConns(50)
+
+	s := &Service{db: db}
+
+	http.ListenAndServe(":8080", s)
+}
+
+type Service struct {
+	db *sql.DB
+}
+
+func (s *Service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	db := s.db
+	switch r.URL.Path {
+	default:
+		http.Error(w, "not found", http.StatusNotFound)
+		return
+	case "/healthz":
+		ctx, cancel := context.WithTimeout(r.Context(), 1*time.Second)
+		defer cancel()
+
+		err := s.db.PingContext(ctx)
+		if err != nil {
+			http.Error(w, fmt.Sprintf("db down: %v", err), http.StatusFailedDependency)
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		return
+	case "/quick-action":
+		// This is a short SELECT. Use the request context as the base of
+		// the context timeout.
+		ctx, cancel := context.WithTimeout(r.Context(), 3*time.Second)
+		defer cancel()
+
+		id := 5
+		org := 10
+		var name string
+		err := db.QueryRowContext(ctx, `
+select
+	p.name
+from
+	people as p
+	join organization as o on p.organization = o.id
+where
+	p.id = :id
+	and o.id = :org
+;`,
+			sql.Named("id", id),
+			sql.Named("org", org),
+		).Scan(&name)
+		if err != nil {
+			if err == sql.ErrNoRows {
+				http.Error(w, "not found", http.StatusNotFound)
+				return
+			}
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		io.WriteString(w, name)
+		return
+	case "/long-action":
+		// This is a long SELECT. Use the request context as the base of
+		// the context timeout, but give it some time to finish. If
+		// the client cancels before the query is done the query will also
+		// be canceled.
+		ctx, cancel := context.WithTimeout(r.Context(), 60*time.Second)
+		defer cancel()
+
+		var names []string
+		rows, err := db.QueryContext(ctx, "select p.name from people as p where p.active = true;")
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		for rows.Next() {
+			var name string
+			err = rows.Scan(&name)
+			if err != nil {
+				break
+			}
+			names = append(names, name)
+		}
+		// Check for errors during rows "Close".
+		// This may be more important if multiple statements are executed
+		// in a single batch and rows were written as well as read.
+		if closeErr := rows.Close(); closeErr != nil {
+			http.Error(w, closeErr.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		// Check for row scan error.
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		// Check for errors during row iteration.
+		if err = rows.Err(); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		json.NewEncoder(w).Encode(names)
+		return
+	case "/async-action":
+		// This action has side effects that we want to preserve
+		// even if the client cancels the HTTP request part way through.
+		// For this we do not use the http request context as a base for
+		// the timeout.
+		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+		defer cancel()
+
+		var orderRef = "ABC123"
+		tx, err := db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelSerializable})
+		_, err = tx.ExecContext(ctx, "stored_proc_name", orderRef)
+
+		if err != nil {
+			tx.Rollback()
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		err = tx.Commit()
+		if err != nil {
+			http.Error(w, "action in unknown state, check state before attempting again", http.StatusInternalServerError)
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		return
+	}
+}
diff --git a/src/database/sql/example_test.go b/src/database/sql/example_test.go
new file mode 100644
index 0000000..aafb0e3
--- /dev/null
+++ b/src/database/sql/example_test.go
@@ -0,0 +1,369 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sql_test
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"log"
+	"strings"
+	"time"
+)
+
+var (
+	ctx context.Context
+	db  *sql.DB
+)
+
+func ExampleDB_QueryContext() {
+	age := 27
+	rows, err := db.QueryContext(ctx, "SELECT name FROM users WHERE age=?", age)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer rows.Close()
+	names := make([]string, 0)
+
+	for rows.Next() {
+		var name string
+		if err := rows.Scan(&name); err != nil {
+			// Check for a scan error.
+			// Query rows will be closed with defer.
+			log.Fatal(err)
+		}
+		names = append(names, name)
+	}
+	// If the database is being written to ensure to check for Close
+	// errors that may be returned from the driver. The query may
+	// encounter an auto-commit error and be forced to rollback changes.
+	rerr := rows.Close()
+	if rerr != nil {
+		log.Fatal(rerr)
+	}
+
+	// Rows.Err will report the last error encountered by Rows.Scan.
+	if err := rows.Err(); err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("%s are %d years old", strings.Join(names, ", "), age)
+}
+
+func ExampleDB_QueryRowContext() {
+	id := 123
+	var username string
+	var created time.Time
+	err := db.QueryRowContext(ctx, "SELECT username, created_at FROM users WHERE id=?", id).Scan(&username, &created)
+	switch {
+	case err == sql.ErrNoRows:
+		log.Printf("no user with id %d\n", id)
+	case err != nil:
+		log.Fatalf("query error: %v\n", err)
+	default:
+		log.Printf("username is %q, account created on %s\n", username, created)
+	}
+}
+
+func ExampleDB_ExecContext() {
+	id := 47
+	result, err := db.ExecContext(ctx, "UPDATE balances SET balance = balance + 10 WHERE user_id = ?", id)
+	if err != nil {
+		log.Fatal(err)
+	}
+	rows, err := result.RowsAffected()
+	if err != nil {
+		log.Fatal(err)
+	}
+	if rows != 1 {
+		log.Fatalf("expected to affect 1 row, affected %d", rows)
+	}
+}
+
+func ExampleDB_Query_multipleResultSets() {
+	age := 27
+	q := `
+create temp table uid (id bigint); -- Create temp table for queries.
+insert into uid
+select id from users where age < ?; -- Populate temp table.
+
+-- First result set.
+select
+	users.id, name
+from
+	users
+	join uid on users.id = uid.id
+;
+
+-- Second result set.
+select 
+	ur.user, ur.role
+from
+	user_roles as ur
+	join uid on uid.id = ur.user
+;
+	`
+	rows, err := db.Query(q, age)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var (
+			id   int64
+			name string
+		)
+		if err := rows.Scan(&id, &name); err != nil {
+			log.Fatal(err)
+		}
+		log.Printf("id %d name is %s\n", id, name)
+	}
+	if !rows.NextResultSet() {
+		log.Fatalf("expected more result sets: %v", rows.Err())
+	}
+	var roleMap = map[int64]string{
+		1: "user",
+		2: "admin",
+		3: "gopher",
+	}
+	for rows.Next() {
+		var (
+			id   int64
+			role int64
+		)
+		if err := rows.Scan(&id, &role); err != nil {
+			log.Fatal(err)
+		}
+		log.Printf("id %d has role %s\n", id, roleMap[role])
+	}
+	if err := rows.Err(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func ExampleDB_PingContext() {
+	// Ping and PingContext may be used to determine if communication with
+	// the database server is still possible.
+	//
+	// When used in a command line application Ping may be used to establish
+	// that further queries are possible; that the provided DSN is valid.
+	//
+	// When used in long running service Ping may be part of the health
+	// checking system.
+
+	ctx, cancel := context.WithTimeout(ctx, 1*time.Second)
+	defer cancel()
+
+	status := "up"
+	if err := db.PingContext(ctx); err != nil {
+		status = "down"
+	}
+	log.Println(status)
+}
+
+func ExampleDB_Prepare() {
+	projects := []struct {
+		mascot  string
+		release int
+	}{
+		{"tux", 1991},
+		{"duke", 1996},
+		{"gopher", 2009},
+		{"moby dock", 2013},
+	}
+
+	stmt, err := db.Prepare("INSERT INTO projects(id, mascot, release, category) VALUES( ?, ?, ?, ? )")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer stmt.Close() // Prepared statements take up server resources and should be closed after use.
+
+	for id, project := range projects {
+		if _, err := stmt.Exec(id+1, project.mascot, project.release, "open source"); err != nil {
+			log.Fatal(err)
+		}
+	}
+}
+
+func ExampleTx_Prepare() {
+	projects := []struct {
+		mascot  string
+		release int
+	}{
+		{"tux", 1991},
+		{"duke", 1996},
+		{"gopher", 2009},
+		{"moby dock", 2013},
+	}
+
+	tx, err := db.Begin()
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer tx.Rollback() // The rollback will be ignored if the tx has been committed later in the function.
+
+	stmt, err := tx.Prepare("INSERT INTO projects(id, mascot, release, category) VALUES( ?, ?, ?, ? )")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer stmt.Close() // Prepared statements take up server resources and should be closed after use.
+
+	for id, project := range projects {
+		if _, err := stmt.Exec(id+1, project.mascot, project.release, "open source"); err != nil {
+			log.Fatal(err)
+		}
+	}
+	if err := tx.Commit(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func ExampleDB_BeginTx() {
+	tx, err := db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelSerializable})
+	if err != nil {
+		log.Fatal(err)
+	}
+	id := 37
+	_, execErr := tx.Exec(`UPDATE users SET status = ? WHERE id = ?`, "paid", id)
+	if execErr != nil {
+		_ = tx.Rollback()
+		log.Fatal(execErr)
+	}
+	if err := tx.Commit(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func ExampleConn_ExecContext() {
+	// A *DB is a pool of connections. Call Conn to reserve a connection for
+	// exclusive use.
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer conn.Close() // Return the connection to the pool.
+	id := 41
+	result, err := conn.ExecContext(ctx, `UPDATE balances SET balance = balance + 10 WHERE user_id = ?;`, id)
+	if err != nil {
+		log.Fatal(err)
+	}
+	rows, err := result.RowsAffected()
+	if err != nil {
+		log.Fatal(err)
+	}
+	if rows != 1 {
+		log.Fatalf("expected single row affected, got %d rows affected", rows)
+	}
+}
+
+func ExampleTx_ExecContext() {
+	tx, err := db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelSerializable})
+	if err != nil {
+		log.Fatal(err)
+	}
+	id := 37
+	_, execErr := tx.ExecContext(ctx, "UPDATE users SET status = ? WHERE id = ?", "paid", id)
+	if execErr != nil {
+		if rollbackErr := tx.Rollback(); rollbackErr != nil {
+			log.Fatalf("update failed: %v, unable to rollback: %v\n", execErr, rollbackErr)
+		}
+		log.Fatalf("update failed: %v", execErr)
+	}
+	if err := tx.Commit(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func ExampleTx_Rollback() {
+	tx, err := db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelSerializable})
+	if err != nil {
+		log.Fatal(err)
+	}
+	id := 53
+	_, err = tx.ExecContext(ctx, "UPDATE drivers SET status = ? WHERE id = ?;", "assigned", id)
+	if err != nil {
+		if rollbackErr := tx.Rollback(); rollbackErr != nil {
+			log.Fatalf("update drivers: unable to rollback: %v", rollbackErr)
+		}
+		log.Fatal(err)
+	}
+	_, err = tx.ExecContext(ctx, "UPDATE pickups SET driver_id = $1;", id)
+	if err != nil {
+		if rollbackErr := tx.Rollback(); rollbackErr != nil {
+			log.Fatalf("update failed: %v, unable to back: %v", err, rollbackErr)
+		}
+		log.Fatal(err)
+	}
+	if err := tx.Commit(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func ExampleStmt() {
+	// In normal use, create one Stmt when your process starts.
+	stmt, err := db.PrepareContext(ctx, "SELECT username FROM users WHERE id = ?")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer stmt.Close()
+
+	// Then reuse it each time you need to issue the query.
+	id := 43
+	var username string
+	err = stmt.QueryRowContext(ctx, id).Scan(&username)
+	switch {
+	case err == sql.ErrNoRows:
+		log.Fatalf("no user with id %d", id)
+	case err != nil:
+		log.Fatal(err)
+	default:
+		log.Printf("username is %s\n", username)
+	}
+}
+
+func ExampleStmt_QueryRowContext() {
+	// In normal use, create one Stmt when your process starts.
+	stmt, err := db.PrepareContext(ctx, "SELECT username FROM users WHERE id = ?")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer stmt.Close()
+
+	// Then reuse it each time you need to issue the query.
+	id := 43
+	var username string
+	err = stmt.QueryRowContext(ctx, id).Scan(&username)
+	switch {
+	case err == sql.ErrNoRows:
+		log.Fatalf("no user with id %d", id)
+	case err != nil:
+		log.Fatal(err)
+	default:
+		log.Printf("username is %s\n", username)
+	}
+}
+
+func ExampleRows() {
+	age := 27
+	rows, err := db.QueryContext(ctx, "SELECT name FROM users WHERE age=?", age)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer rows.Close()
+
+	names := make([]string, 0)
+	for rows.Next() {
+		var name string
+		if err := rows.Scan(&name); err != nil {
+			log.Fatal(err)
+		}
+		names = append(names, name)
+	}
+	// Check for errors from iterating over rows.
+	if err := rows.Err(); err != nil {
+		log.Fatal(err)
+	}
+	log.Printf("%s are %d years old", strings.Join(names, ", "), age)
+}
diff --git a/src/database/sql/fakedb_test.go b/src/database/sql/fakedb_test.go
new file mode 100644
index 0000000..7605a2a
--- /dev/null
+++ b/src/database/sql/fakedb_test.go
@@ -0,0 +1,1238 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sql
+
+import (
+	"context"
+	"database/sql/driver"
+	"errors"
+	"fmt"
+	"io"
+	"reflect"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+// fakeDriver is a fake database that implements Go's driver.Driver
+// interface, just for testing.
+//
+// It speaks a query language that's semantically similar to but
+// syntactically different and simpler than SQL.  The syntax is as
+// follows:
+//
+//   WIPE
+//   CREATE|<tablename>|<col>=<type>,<col>=<type>,...
+//     where types are: "string", [u]int{8,16,32,64}, "bool"
+//   INSERT|<tablename>|col=val,col2=val2,col3=?
+//   SELECT|<tablename>|projectcol1,projectcol2|filtercol=?,filtercol2=?
+//   SELECT|<tablename>|projectcol1,projectcol2|filtercol=?param1,filtercol2=?param2
+//
+// Any of these can be preceded by PANIC|<method>|, to cause the
+// named method on fakeStmt to panic.
+//
+// Any of these can be proceeded by WAIT|<duration>|, to cause the
+// named method on fakeStmt to sleep for the specified duration.
+//
+// Multiple of these can be combined when separated with a semicolon.
+//
+// When opening a fakeDriver's database, it starts empty with no
+// tables. All tables and data are stored in memory only.
+type fakeDriver struct {
+	mu         sync.Mutex // guards 3 following fields
+	openCount  int        // conn opens
+	closeCount int        // conn closes
+	waitCh     chan struct{}
+	waitingCh  chan struct{}
+	dbs        map[string]*fakeDB
+}
+
+type fakeConnector struct {
+	name string
+
+	waiter func(context.Context)
+}
+
+func (c *fakeConnector) Connect(context.Context) (driver.Conn, error) {
+	conn, err := fdriver.Open(c.name)
+	conn.(*fakeConn).waiter = c.waiter
+	return conn, err
+}
+
+func (c *fakeConnector) Driver() driver.Driver {
+	return fdriver
+}
+
+type fakeDriverCtx struct {
+	fakeDriver
+}
+
+var _ driver.DriverContext = &fakeDriverCtx{}
+
+func (cc *fakeDriverCtx) OpenConnector(name string) (driver.Connector, error) {
+	return &fakeConnector{name: name}, nil
+}
+
+type fakeDB struct {
+	name string
+
+	mu       sync.Mutex
+	tables   map[string]*table
+	badConn  bool
+	allowAny bool
+}
+
+type table struct {
+	mu      sync.Mutex
+	colname []string
+	coltype []string
+	rows    []*row
+}
+
+func (t *table) columnIndex(name string) int {
+	for n, nname := range t.colname {
+		if name == nname {
+			return n
+		}
+	}
+	return -1
+}
+
+type row struct {
+	cols []interface{} // must be same size as its table colname + coltype
+}
+
+type memToucher interface {
+	// touchMem reads & writes some memory, to help find data races.
+	touchMem()
+}
+
+type fakeConn struct {
+	db *fakeDB // where to return ourselves to
+
+	currTx *fakeTx
+
+	// Every operation writes to line to enable the race detector
+	// check for data races.
+	line int64
+
+	// Stats for tests:
+	mu          sync.Mutex
+	stmtsMade   int
+	stmtsClosed int
+	numPrepare  int
+
+	// bad connection tests; see isBad()
+	bad       bool
+	stickyBad bool
+
+	skipDirtySession bool // tests that use Conn should set this to true.
+
+	// dirtySession tests ResetSession, true if a query has executed
+	// until ResetSession is called.
+	dirtySession bool
+
+	// The waiter is called before each query. May be used in place of the "WAIT"
+	// directive.
+	waiter func(context.Context)
+}
+
+func (c *fakeConn) touchMem() {
+	c.line++
+}
+
+func (c *fakeConn) incrStat(v *int) {
+	c.mu.Lock()
+	*v++
+	c.mu.Unlock()
+}
+
+type fakeTx struct {
+	c *fakeConn
+}
+
+type boundCol struct {
+	Column      string
+	Placeholder string
+	Ordinal     int
+}
+
+type fakeStmt struct {
+	memToucher
+	c *fakeConn
+	q string // just for debugging
+
+	cmd   string
+	table string
+	panic string
+	wait  time.Duration
+
+	next *fakeStmt // used for returning multiple results.
+
+	closed bool
+
+	colName      []string      // used by CREATE, INSERT, SELECT (selected columns)
+	colType      []string      // used by CREATE
+	colValue     []interface{} // used by INSERT (mix of strings and "?" for bound params)
+	placeholders int           // used by INSERT/SELECT: number of ? params
+
+	whereCol []boundCol // used by SELECT (all placeholders)
+
+	placeholderConverter []driver.ValueConverter // used by INSERT
+}
+
+var fdriver driver.Driver = &fakeDriver{}
+
+func init() {
+	Register("test", fdriver)
+}
+
+func contains(list []string, y string) bool {
+	for _, x := range list {
+		if x == y {
+			return true
+		}
+	}
+	return false
+}
+
+type Dummy struct {
+	driver.Driver
+}
+
+func TestDrivers(t *testing.T) {
+	unregisterAllDrivers()
+	Register("test", fdriver)
+	Register("invalid", Dummy{})
+	all := Drivers()
+	if len(all) < 2 || !sort.StringsAreSorted(all) || !contains(all, "test") || !contains(all, "invalid") {
+		t.Fatalf("Drivers = %v, want sorted list with at least [invalid, test]", all)
+	}
+}
+
+// hook to simulate connection failures
+var hookOpenErr struct {
+	sync.Mutex
+	fn func() error
+}
+
+func setHookOpenErr(fn func() error) {
+	hookOpenErr.Lock()
+	defer hookOpenErr.Unlock()
+	hookOpenErr.fn = fn
+}
+
+// Supports dsn forms:
+//    <dbname>
+//    <dbname>;<opts>  (only currently supported option is `badConn`,
+//                      which causes driver.ErrBadConn to be returned on
+//                      every other conn.Begin())
+func (d *fakeDriver) Open(dsn string) (driver.Conn, error) {
+	hookOpenErr.Lock()
+	fn := hookOpenErr.fn
+	hookOpenErr.Unlock()
+	if fn != nil {
+		if err := fn(); err != nil {
+			return nil, err
+		}
+	}
+	parts := strings.Split(dsn, ";")
+	if len(parts) < 1 {
+		return nil, errors.New("fakedb: no database name")
+	}
+	name := parts[0]
+
+	db := d.getDB(name)
+
+	d.mu.Lock()
+	d.openCount++
+	d.mu.Unlock()
+	conn := &fakeConn{db: db}
+
+	if len(parts) >= 2 && parts[1] == "badConn" {
+		conn.bad = true
+	}
+	if d.waitCh != nil {
+		d.waitingCh <- struct{}{}
+		<-d.waitCh
+		d.waitCh = nil
+		d.waitingCh = nil
+	}
+	return conn, nil
+}
+
+func (d *fakeDriver) getDB(name string) *fakeDB {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	if d.dbs == nil {
+		d.dbs = make(map[string]*fakeDB)
+	}
+	db, ok := d.dbs[name]
+	if !ok {
+		db = &fakeDB{name: name}
+		d.dbs[name] = db
+	}
+	return db
+}
+
+func (db *fakeDB) wipe() {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	db.tables = nil
+}
+
+func (db *fakeDB) createTable(name string, columnNames, columnTypes []string) error {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	if db.tables == nil {
+		db.tables = make(map[string]*table)
+	}
+	if _, exist := db.tables[name]; exist {
+		return fmt.Errorf("fakedb: table %q already exists", name)
+	}
+	if len(columnNames) != len(columnTypes) {
+		return fmt.Errorf("fakedb: create table of %q len(names) != len(types): %d vs %d",
+			name, len(columnNames), len(columnTypes))
+	}
+	db.tables[name] = &table{colname: columnNames, coltype: columnTypes}
+	return nil
+}
+
+// must be called with db.mu lock held
+func (db *fakeDB) table(table string) (*table, bool) {
+	if db.tables == nil {
+		return nil, false
+	}
+	t, ok := db.tables[table]
+	return t, ok
+}
+
+func (db *fakeDB) columnType(table, column string) (typ string, ok bool) {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	t, ok := db.table(table)
+	if !ok {
+		return
+	}
+	for n, cname := range t.colname {
+		if cname == column {
+			return t.coltype[n], true
+		}
+	}
+	return "", false
+}
+
+func (c *fakeConn) isBad() bool {
+	if c.stickyBad {
+		return true
+	} else if c.bad {
+		if c.db == nil {
+			return false
+		}
+		// alternate between bad conn and not bad conn
+		c.db.badConn = !c.db.badConn
+		return c.db.badConn
+	} else {
+		return false
+	}
+}
+
+func (c *fakeConn) isDirtyAndMark() bool {
+	if c.skipDirtySession {
+		return false
+	}
+	if c.currTx != nil {
+		c.dirtySession = true
+		return false
+	}
+	if c.dirtySession {
+		return true
+	}
+	c.dirtySession = true
+	return false
+}
+
+func (c *fakeConn) Begin() (driver.Tx, error) {
+	if c.isBad() {
+		return nil, driver.ErrBadConn
+	}
+	if c.currTx != nil {
+		return nil, errors.New("fakedb: already in a transaction")
+	}
+	c.touchMem()
+	c.currTx = &fakeTx{c: c}
+	return c.currTx, nil
+}
+
+var hookPostCloseConn struct {
+	sync.Mutex
+	fn func(*fakeConn, error)
+}
+
+func setHookpostCloseConn(fn func(*fakeConn, error)) {
+	hookPostCloseConn.Lock()
+	defer hookPostCloseConn.Unlock()
+	hookPostCloseConn.fn = fn
+}
+
+var testStrictClose *testing.T
+
+// setStrictFakeConnClose sets the t to Errorf on when fakeConn.Close
+// fails to close. If nil, the check is disabled.
+func setStrictFakeConnClose(t *testing.T) {
+	testStrictClose = t
+}
+
+func (c *fakeConn) ResetSession(ctx context.Context) error {
+	c.dirtySession = false
+	c.currTx = nil
+	if c.isBad() {
+		return driver.ErrBadConn
+	}
+	return nil
+}
+
+var _ driver.Validator = (*fakeConn)(nil)
+
+func (c *fakeConn) IsValid() bool {
+	return !c.isBad()
+}
+
+func (c *fakeConn) Close() (err error) {
+	drv := fdriver.(*fakeDriver)
+	defer func() {
+		if err != nil && testStrictClose != nil {
+			testStrictClose.Errorf("failed to close a test fakeConn: %v", err)
+		}
+		hookPostCloseConn.Lock()
+		fn := hookPostCloseConn.fn
+		hookPostCloseConn.Unlock()
+		if fn != nil {
+			fn(c, err)
+		}
+		if err == nil {
+			drv.mu.Lock()
+			drv.closeCount++
+			drv.mu.Unlock()
+		}
+	}()
+	c.touchMem()
+	if c.currTx != nil {
+		return errors.New("fakedb: can't close fakeConn; in a Transaction")
+	}
+	if c.db == nil {
+		return errors.New("fakedb: can't close fakeConn; already closed")
+	}
+	if c.stmtsMade > c.stmtsClosed {
+		return errors.New("fakedb: can't close; dangling statement(s)")
+	}
+	c.db = nil
+	return nil
+}
+
+func checkSubsetTypes(allowAny bool, args []driver.NamedValue) error {
+	for _, arg := range args {
+		switch arg.Value.(type) {
+		case int64, float64, bool, nil, []byte, string, time.Time:
+		default:
+			if !allowAny {
+				return fmt.Errorf("fakedb: invalid argument ordinal %[1]d: %[2]v, type %[2]T", arg.Ordinal, arg.Value)
+			}
+		}
+	}
+	return nil
+}
+
+func (c *fakeConn) Exec(query string, args []driver.Value) (driver.Result, error) {
+	// Ensure that ExecContext is called if available.
+	panic("ExecContext was not called.")
+}
+
+func (c *fakeConn) ExecContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Result, error) {
+	// This is an optional interface, but it's implemented here
+	// just to check that all the args are of the proper types.
+	// ErrSkip is returned so the caller acts as if we didn't
+	// implement this at all.
+	err := checkSubsetTypes(c.db.allowAny, args)
+	if err != nil {
+		return nil, err
+	}
+	return nil, driver.ErrSkip
+}
+
+func (c *fakeConn) Query(query string, args []driver.Value) (driver.Rows, error) {
+	// Ensure that ExecContext is called if available.
+	panic("QueryContext was not called.")
+}
+
+func (c *fakeConn) QueryContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Rows, error) {
+	// This is an optional interface, but it's implemented here
+	// just to check that all the args are of the proper types.
+	// ErrSkip is returned so the caller acts as if we didn't
+	// implement this at all.
+	err := checkSubsetTypes(c.db.allowAny, args)
+	if err != nil {
+		return nil, err
+	}
+	return nil, driver.ErrSkip
+}
+
+func errf(msg string, args ...interface{}) error {
+	return errors.New("fakedb: " + fmt.Sprintf(msg, args...))
+}
+
+// parts are table|selectCol1,selectCol2|whereCol=?,whereCol2=?
+// (note that where columns must always contain ? marks,
+//  just a limitation for fakedb)
+func (c *fakeConn) prepareSelect(stmt *fakeStmt, parts []string) (*fakeStmt, error) {
+	if len(parts) != 3 {
+		stmt.Close()
+		return nil, errf("invalid SELECT syntax with %d parts; want 3", len(parts))
+	}
+	stmt.table = parts[0]
+
+	stmt.colName = strings.Split(parts[1], ",")
+	for n, colspec := range strings.Split(parts[2], ",") {
+		if colspec == "" {
+			continue
+		}
+		nameVal := strings.Split(colspec, "=")
+		if len(nameVal) != 2 {
+			stmt.Close()
+			return nil, errf("SELECT on table %q has invalid column spec of %q (index %d)", stmt.table, colspec, n)
+		}
+		column, value := nameVal[0], nameVal[1]
+		_, ok := c.db.columnType(stmt.table, column)
+		if !ok {
+			stmt.Close()
+			return nil, errf("SELECT on table %q references non-existent column %q", stmt.table, column)
+		}
+		if !strings.HasPrefix(value, "?") {
+			stmt.Close()
+			return nil, errf("SELECT on table %q has pre-bound value for where column %q; need a question mark",
+				stmt.table, column)
+		}
+		stmt.placeholders++
+		stmt.whereCol = append(stmt.whereCol, boundCol{Column: column, Placeholder: value, Ordinal: stmt.placeholders})
+	}
+	return stmt, nil
+}
+
+// parts are table|col=type,col2=type2
+func (c *fakeConn) prepareCreate(stmt *fakeStmt, parts []string) (*fakeStmt, error) {
+	if len(parts) != 2 {
+		stmt.Close()
+		return nil, errf("invalid CREATE syntax with %d parts; want 2", len(parts))
+	}
+	stmt.table = parts[0]
+	for n, colspec := range strings.Split(parts[1], ",") {
+		nameType := strings.Split(colspec, "=")
+		if len(nameType) != 2 {
+			stmt.Close()
+			return nil, errf("CREATE table %q has invalid column spec of %q (index %d)", stmt.table, colspec, n)
+		}
+		stmt.colName = append(stmt.colName, nameType[0])
+		stmt.colType = append(stmt.colType, nameType[1])
+	}
+	return stmt, nil
+}
+
+// parts are table|col=?,col2=val
+func (c *fakeConn) prepareInsert(ctx context.Context, stmt *fakeStmt, parts []string) (*fakeStmt, error) {
+	if len(parts) != 2 {
+		stmt.Close()
+		return nil, errf("invalid INSERT syntax with %d parts; want 2", len(parts))
+	}
+	stmt.table = parts[0]
+	for n, colspec := range strings.Split(parts[1], ",") {
+		nameVal := strings.Split(colspec, "=")
+		if len(nameVal) != 2 {
+			stmt.Close()
+			return nil, errf("INSERT table %q has invalid column spec of %q (index %d)", stmt.table, colspec, n)
+		}
+		column, value := nameVal[0], nameVal[1]
+		ctype, ok := c.db.columnType(stmt.table, column)
+		if !ok {
+			stmt.Close()
+			return nil, errf("INSERT table %q references non-existent column %q", stmt.table, column)
+		}
+		stmt.colName = append(stmt.colName, column)
+
+		if !strings.HasPrefix(value, "?") {
+			var subsetVal interface{}
+			// Convert to driver subset type
+			switch ctype {
+			case "string":
+				subsetVal = []byte(value)
+			case "blob":
+				subsetVal = []byte(value)
+			case "int32":
+				i, err := strconv.Atoi(value)
+				if err != nil {
+					stmt.Close()
+					return nil, errf("invalid conversion to int32 from %q", value)
+				}
+				subsetVal = int64(i) // int64 is a subset type, but not int32
+			case "table": // For testing cursor reads.
+				c.skipDirtySession = true
+				vparts := strings.Split(value, "!")
+
+				substmt, err := c.PrepareContext(ctx, fmt.Sprintf("SELECT|%s|%s|", vparts[0], strings.Join(vparts[1:], ",")))
+				if err != nil {
+					return nil, err
+				}
+				cursor, err := (substmt.(driver.StmtQueryContext)).QueryContext(ctx, []driver.NamedValue{})
+				substmt.Close()
+				if err != nil {
+					return nil, err
+				}
+				subsetVal = cursor
+			default:
+				stmt.Close()
+				return nil, errf("unsupported conversion for pre-bound parameter %q to type %q", value, ctype)
+			}
+			stmt.colValue = append(stmt.colValue, subsetVal)
+		} else {
+			stmt.placeholders++
+			stmt.placeholderConverter = append(stmt.placeholderConverter, converterForType(ctype))
+			stmt.colValue = append(stmt.colValue, value)
+		}
+	}
+	return stmt, nil
+}
+
+// hook to simulate broken connections
+var hookPrepareBadConn func() bool
+
+func (c *fakeConn) Prepare(query string) (driver.Stmt, error) {
+	panic("use PrepareContext")
+}
+
+func (c *fakeConn) PrepareContext(ctx context.Context, query string) (driver.Stmt, error) {
+	c.numPrepare++
+	if c.db == nil {
+		panic("nil c.db; conn = " + fmt.Sprintf("%#v", c))
+	}
+
+	if c.stickyBad || (hookPrepareBadConn != nil && hookPrepareBadConn()) {
+		return nil, driver.ErrBadConn
+	}
+
+	c.touchMem()
+	var firstStmt, prev *fakeStmt
+	for _, query := range strings.Split(query, ";") {
+		parts := strings.Split(query, "|")
+		if len(parts) < 1 {
+			return nil, errf("empty query")
+		}
+		stmt := &fakeStmt{q: query, c: c, memToucher: c}
+		if firstStmt == nil {
+			firstStmt = stmt
+		}
+		if len(parts) >= 3 {
+			switch parts[0] {
+			case "PANIC":
+				stmt.panic = parts[1]
+				parts = parts[2:]
+			case "WAIT":
+				wait, err := time.ParseDuration(parts[1])
+				if err != nil {
+					return nil, errf("expected section after WAIT to be a duration, got %q %v", parts[1], err)
+				}
+				parts = parts[2:]
+				stmt.wait = wait
+			}
+		}
+		cmd := parts[0]
+		stmt.cmd = cmd
+		parts = parts[1:]
+
+		if c.waiter != nil {
+			c.waiter(ctx)
+		}
+
+		if stmt.wait > 0 {
+			wait := time.NewTimer(stmt.wait)
+			select {
+			case <-wait.C:
+			case <-ctx.Done():
+				wait.Stop()
+				return nil, ctx.Err()
+			}
+		}
+
+		c.incrStat(&c.stmtsMade)
+		var err error
+		switch cmd {
+		case "WIPE":
+			// Nothing
+		case "SELECT":
+			stmt, err = c.prepareSelect(stmt, parts)
+		case "CREATE":
+			stmt, err = c.prepareCreate(stmt, parts)
+		case "INSERT":
+			stmt, err = c.prepareInsert(ctx, stmt, parts)
+		case "NOSERT":
+			// Do all the prep-work like for an INSERT but don't actually insert the row.
+			// Used for some of the concurrent tests.
+			stmt, err = c.prepareInsert(ctx, stmt, parts)
+		default:
+			stmt.Close()
+			return nil, errf("unsupported command type %q", cmd)
+		}
+		if err != nil {
+			return nil, err
+		}
+		if prev != nil {
+			prev.next = stmt
+		}
+		prev = stmt
+	}
+	return firstStmt, nil
+}
+
+func (s *fakeStmt) ColumnConverter(idx int) driver.ValueConverter {
+	if s.panic == "ColumnConverter" {
+		panic(s.panic)
+	}
+	if len(s.placeholderConverter) == 0 {
+		return driver.DefaultParameterConverter
+	}
+	return s.placeholderConverter[idx]
+}
+
+func (s *fakeStmt) Close() error {
+	if s.panic == "Close" {
+		panic(s.panic)
+	}
+	if s.c == nil {
+		panic("nil conn in fakeStmt.Close")
+	}
+	if s.c.db == nil {
+		panic("in fakeStmt.Close, conn's db is nil (already closed)")
+	}
+	s.touchMem()
+	if !s.closed {
+		s.c.incrStat(&s.c.stmtsClosed)
+		s.closed = true
+	}
+	if s.next != nil {
+		s.next.Close()
+	}
+	return nil
+}
+
+var errClosed = errors.New("fakedb: statement has been closed")
+
+// hook to simulate broken connections
+var hookExecBadConn func() bool
+
+func (s *fakeStmt) Exec(args []driver.Value) (driver.Result, error) {
+	panic("Using ExecContext")
+}
+
+var errFakeConnSessionDirty = errors.New("fakedb: session is dirty")
+
+func (s *fakeStmt) ExecContext(ctx context.Context, args []driver.NamedValue) (driver.Result, error) {
+	if s.panic == "Exec" {
+		panic(s.panic)
+	}
+	if s.closed {
+		return nil, errClosed
+	}
+
+	if s.c.stickyBad || (hookExecBadConn != nil && hookExecBadConn()) {
+		return nil, driver.ErrBadConn
+	}
+	if s.c.isDirtyAndMark() {
+		return nil, errFakeConnSessionDirty
+	}
+
+	err := checkSubsetTypes(s.c.db.allowAny, args)
+	if err != nil {
+		return nil, err
+	}
+	s.touchMem()
+
+	if s.wait > 0 {
+		time.Sleep(s.wait)
+	}
+
+	select {
+	default:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+
+	db := s.c.db
+	switch s.cmd {
+	case "WIPE":
+		db.wipe()
+		return driver.ResultNoRows, nil
+	case "CREATE":
+		if err := db.createTable(s.table, s.colName, s.colType); err != nil {
+			return nil, err
+		}
+		return driver.ResultNoRows, nil
+	case "INSERT":
+		return s.execInsert(args, true)
+	case "NOSERT":
+		// Do all the prep-work like for an INSERT but don't actually insert the row.
+		// Used for some of the concurrent tests.
+		return s.execInsert(args, false)
+	}
+	return nil, fmt.Errorf("fakedb: unimplemented statement Exec command type of %q", s.cmd)
+}
+
+// When doInsert is true, add the row to the table.
+// When doInsert is false do prep-work and error checking, but don't
+// actually add the row to the table.
+func (s *fakeStmt) execInsert(args []driver.NamedValue, doInsert bool) (driver.Result, error) {
+	db := s.c.db
+	if len(args) != s.placeholders {
+		panic("error in pkg db; should only get here if size is correct")
+	}
+	db.mu.Lock()
+	t, ok := db.table(s.table)
+	db.mu.Unlock()
+	if !ok {
+		return nil, fmt.Errorf("fakedb: table %q doesn't exist", s.table)
+	}
+
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	var cols []interface{}
+	if doInsert {
+		cols = make([]interface{}, len(t.colname))
+	}
+	argPos := 0
+	for n, colname := range s.colName {
+		colidx := t.columnIndex(colname)
+		if colidx == -1 {
+			return nil, fmt.Errorf("fakedb: column %q doesn't exist or dropped since prepared statement was created", colname)
+		}
+		var val interface{}
+		if strvalue, ok := s.colValue[n].(string); ok && strings.HasPrefix(strvalue, "?") {
+			if strvalue == "?" {
+				val = args[argPos].Value
+			} else {
+				// Assign value from argument placeholder name.
+				for _, a := range args {
+					if a.Name == strvalue[1:] {
+						val = a.Value
+						break
+					}
+				}
+			}
+			argPos++
+		} else {
+			val = s.colValue[n]
+		}
+		if doInsert {
+			cols[colidx] = val
+		}
+	}
+
+	if doInsert {
+		t.rows = append(t.rows, &row{cols: cols})
+	}
+	return driver.RowsAffected(1), nil
+}
+
+// hook to simulate broken connections
+var hookQueryBadConn func() bool
+
+func (s *fakeStmt) Query(args []driver.Value) (driver.Rows, error) {
+	panic("Use QueryContext")
+}
+
+func (s *fakeStmt) QueryContext(ctx context.Context, args []driver.NamedValue) (driver.Rows, error) {
+	if s.panic == "Query" {
+		panic(s.panic)
+	}
+	if s.closed {
+		return nil, errClosed
+	}
+
+	if s.c.stickyBad || (hookQueryBadConn != nil && hookQueryBadConn()) {
+		return nil, driver.ErrBadConn
+	}
+	if s.c.isDirtyAndMark() {
+		return nil, errFakeConnSessionDirty
+	}
+
+	err := checkSubsetTypes(s.c.db.allowAny, args)
+	if err != nil {
+		return nil, err
+	}
+
+	s.touchMem()
+	db := s.c.db
+	if len(args) != s.placeholders {
+		panic("error in pkg db; should only get here if size is correct")
+	}
+
+	setMRows := make([][]*row, 0, 1)
+	setColumns := make([][]string, 0, 1)
+	setColType := make([][]string, 0, 1)
+
+	for {
+		db.mu.Lock()
+		t, ok := db.table(s.table)
+		db.mu.Unlock()
+		if !ok {
+			return nil, fmt.Errorf("fakedb: table %q doesn't exist", s.table)
+		}
+
+		if s.table == "magicquery" {
+			if len(s.whereCol) == 2 && s.whereCol[0].Column == "op" && s.whereCol[1].Column == "millis" {
+				if args[0].Value == "sleep" {
+					time.Sleep(time.Duration(args[1].Value.(int64)) * time.Millisecond)
+				}
+			}
+		}
+		if s.table == "tx_status" && s.colName[0] == "tx_status" {
+			txStatus := "autocommit"
+			if s.c.currTx != nil {
+				txStatus = "transaction"
+			}
+			cursor := &rowsCursor{
+				parentMem: s.c,
+				posRow:    -1,
+				rows: [][]*row{
+					[]*row{
+						{
+							cols: []interface{}{
+								txStatus,
+							},
+						},
+					},
+				},
+				cols: [][]string{
+					[]string{
+						"tx_status",
+					},
+				},
+				colType: [][]string{
+					[]string{
+						"string",
+					},
+				},
+				errPos: -1,
+			}
+			return cursor, nil
+		}
+
+		t.mu.Lock()
+
+		colIdx := make(map[string]int) // select column name -> column index in table
+		for _, name := range s.colName {
+			idx := t.columnIndex(name)
+			if idx == -1 {
+				t.mu.Unlock()
+				return nil, fmt.Errorf("fakedb: unknown column name %q", name)
+			}
+			colIdx[name] = idx
+		}
+
+		mrows := []*row{}
+	rows:
+		for _, trow := range t.rows {
+			// Process the where clause, skipping non-match rows. This is lazy
+			// and just uses fmt.Sprintf("%v") to test equality. Good enough
+			// for test code.
+			for _, wcol := range s.whereCol {
+				idx := t.columnIndex(wcol.Column)
+				if idx == -1 {
+					t.mu.Unlock()
+					return nil, fmt.Errorf("fakedb: invalid where clause column %q", wcol)
+				}
+				tcol := trow.cols[idx]
+				if bs, ok := tcol.([]byte); ok {
+					// lazy hack to avoid sprintf %v on a []byte
+					tcol = string(bs)
+				}
+				var argValue interface{}
+				if wcol.Placeholder == "?" {
+					argValue = args[wcol.Ordinal-1].Value
+				} else {
+					// Assign arg value from placeholder name.
+					for _, a := range args {
+						if a.Name == wcol.Placeholder[1:] {
+							argValue = a.Value
+							break
+						}
+					}
+				}
+				if fmt.Sprintf("%v", tcol) != fmt.Sprintf("%v", argValue) {
+					continue rows
+				}
+			}
+			mrow := &row{cols: make([]interface{}, len(s.colName))}
+			for seli, name := range s.colName {
+				mrow.cols[seli] = trow.cols[colIdx[name]]
+			}
+			mrows = append(mrows, mrow)
+		}
+
+		var colType []string
+		for _, column := range s.colName {
+			colType = append(colType, t.coltype[t.columnIndex(column)])
+		}
+
+		t.mu.Unlock()
+
+		setMRows = append(setMRows, mrows)
+		setColumns = append(setColumns, s.colName)
+		setColType = append(setColType, colType)
+
+		if s.next == nil {
+			break
+		}
+		s = s.next
+	}
+
+	cursor := &rowsCursor{
+		parentMem: s.c,
+		posRow:    -1,
+		rows:      setMRows,
+		cols:      setColumns,
+		colType:   setColType,
+		errPos:    -1,
+	}
+	return cursor, nil
+}
+
+func (s *fakeStmt) NumInput() int {
+	if s.panic == "NumInput" {
+		panic(s.panic)
+	}
+	return s.placeholders
+}
+
+// hook to simulate broken connections
+var hookCommitBadConn func() bool
+
+func (tx *fakeTx) Commit() error {
+	tx.c.currTx = nil
+	if hookCommitBadConn != nil && hookCommitBadConn() {
+		return driver.ErrBadConn
+	}
+	tx.c.touchMem()
+	return nil
+}
+
+// hook to simulate broken connections
+var hookRollbackBadConn func() bool
+
+func (tx *fakeTx) Rollback() error {
+	tx.c.currTx = nil
+	if hookRollbackBadConn != nil && hookRollbackBadConn() {
+		return driver.ErrBadConn
+	}
+	tx.c.touchMem()
+	return nil
+}
+
+type rowsCursor struct {
+	parentMem memToucher
+	cols      [][]string
+	colType   [][]string
+	posSet    int
+	posRow    int
+	rows      [][]*row
+	closed    bool
+
+	// errPos and err are for making Next return early with error.
+	errPos int
+	err    error
+
+	// a clone of slices to give out to clients, indexed by the
+	// original slice's first byte address.  we clone them
+	// just so we're able to corrupt them on close.
+	bytesClone map[*byte][]byte
+
+	// Every operation writes to line to enable the race detector
+	// check for data races.
+	// This is separate from the fakeConn.line to allow for drivers that
+	// can start multiple queries on the same transaction at the same time.
+	line int64
+}
+
+func (rc *rowsCursor) touchMem() {
+	rc.parentMem.touchMem()
+	rc.line++
+}
+
+func (rc *rowsCursor) Close() error {
+	rc.touchMem()
+	rc.parentMem.touchMem()
+	rc.closed = true
+	return nil
+}
+
+func (rc *rowsCursor) Columns() []string {
+	return rc.cols[rc.posSet]
+}
+
+func (rc *rowsCursor) ColumnTypeScanType(index int) reflect.Type {
+	return colTypeToReflectType(rc.colType[rc.posSet][index])
+}
+
+var rowsCursorNextHook func(dest []driver.Value) error
+
+func (rc *rowsCursor) Next(dest []driver.Value) error {
+	if rowsCursorNextHook != nil {
+		return rowsCursorNextHook(dest)
+	}
+
+	if rc.closed {
+		return errors.New("fakedb: cursor is closed")
+	}
+	rc.touchMem()
+	rc.posRow++
+	if rc.posRow == rc.errPos {
+		return rc.err
+	}
+	if rc.posRow >= len(rc.rows[rc.posSet]) {
+		return io.EOF // per interface spec
+	}
+	for i, v := range rc.rows[rc.posSet][rc.posRow].cols {
+		// TODO(bradfitz): convert to subset types? naah, I
+		// think the subset types should only be input to
+		// driver, but the sql package should be able to handle
+		// a wider range of types coming out of drivers. all
+		// for ease of drivers, and to prevent drivers from
+		// messing up conversions or doing them differently.
+		dest[i] = v
+
+		if bs, ok := v.([]byte); ok {
+			if rc.bytesClone == nil {
+				rc.bytesClone = make(map[*byte][]byte)
+			}
+			clone, ok := rc.bytesClone[&bs[0]]
+			if !ok {
+				clone = make([]byte, len(bs))
+				copy(clone, bs)
+				rc.bytesClone[&bs[0]] = clone
+			}
+			dest[i] = clone
+		}
+	}
+	return nil
+}
+
+func (rc *rowsCursor) HasNextResultSet() bool {
+	rc.touchMem()
+	return rc.posSet < len(rc.rows)-1
+}
+
+func (rc *rowsCursor) NextResultSet() error {
+	rc.touchMem()
+	if rc.HasNextResultSet() {
+		rc.posSet++
+		rc.posRow = -1
+		return nil
+	}
+	return io.EOF // Per interface spec.
+}
+
+// fakeDriverString is like driver.String, but indirects pointers like
+// DefaultValueConverter.
+//
+// This could be surprising behavior to retroactively apply to
+// driver.String now that Go1 is out, but this is convenient for
+// our TestPointerParamsAndScans.
+//
+type fakeDriverString struct{}
+
+func (fakeDriverString) ConvertValue(v interface{}) (driver.Value, error) {
+	switch c := v.(type) {
+	case string, []byte:
+		return v, nil
+	case *string:
+		if c == nil {
+			return nil, nil
+		}
+		return *c, nil
+	}
+	return fmt.Sprintf("%v", v), nil
+}
+
+type anyTypeConverter struct{}
+
+func (anyTypeConverter) ConvertValue(v interface{}) (driver.Value, error) {
+	return v, nil
+}
+
+func converterForType(typ string) driver.ValueConverter {
+	switch typ {
+	case "bool":
+		return driver.Bool
+	case "nullbool":
+		return driver.Null{Converter: driver.Bool}
+	case "int32":
+		return driver.Int32
+	case "nullint32":
+		return driver.Null{Converter: driver.DefaultParameterConverter}
+	case "string":
+		return driver.NotNull{Converter: fakeDriverString{}}
+	case "nullstring":
+		return driver.Null{Converter: fakeDriverString{}}
+	case "int64":
+		// TODO(coopernurse): add type-specific converter
+		return driver.NotNull{Converter: driver.DefaultParameterConverter}
+	case "nullint64":
+		// TODO(coopernurse): add type-specific converter
+		return driver.Null{Converter: driver.DefaultParameterConverter}
+	case "float64":
+		// TODO(coopernurse): add type-specific converter
+		return driver.NotNull{Converter: driver.DefaultParameterConverter}
+	case "nullfloat64":
+		// TODO(coopernurse): add type-specific converter
+		return driver.Null{Converter: driver.DefaultParameterConverter}
+	case "datetime":
+		return driver.NotNull{Converter: driver.DefaultParameterConverter}
+	case "nulldatetime":
+		return driver.Null{Converter: driver.DefaultParameterConverter}
+	case "any":
+		return anyTypeConverter{}
+	}
+	panic("invalid fakedb column type of " + typ)
+}
+
+func colTypeToReflectType(typ string) reflect.Type {
+	switch typ {
+	case "bool":
+		return reflect.TypeOf(false)
+	case "nullbool":
+		return reflect.TypeOf(NullBool{})
+	case "int32":
+		return reflect.TypeOf(int32(0))
+	case "nullint32":
+		return reflect.TypeOf(NullInt32{})
+	case "string":
+		return reflect.TypeOf("")
+	case "nullstring":
+		return reflect.TypeOf(NullString{})
+	case "int64":
+		return reflect.TypeOf(int64(0))
+	case "nullint64":
+		return reflect.TypeOf(NullInt64{})
+	case "float64":
+		return reflect.TypeOf(float64(0))
+	case "nullfloat64":
+		return reflect.TypeOf(NullFloat64{})
+	case "datetime":
+		return reflect.TypeOf(time.Time{})
+	case "any":
+		return reflect.TypeOf(new(interface{})).Elem()
+	}
+	panic("invalid fakedb column type of " + typ)
+}
diff --git a/src/database/sql/sql.go b/src/database/sql/sql.go
new file mode 100644
index 0000000..726aadb
--- /dev/null
+++ b/src/database/sql/sql.go
@@ -0,0 +1,3295 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package sql provides a generic interface around SQL (or SQL-like)
+// databases.
+//
+// The sql package must be used in conjunction with a database driver.
+// See https://golang.org/s/sqldrivers for a list of drivers.
+//
+// Drivers that do not support context cancellation will not return until
+// after the query is completed.
+//
+// For usage examples, see the wiki page at
+// https://golang.org/s/sqlwiki.
+package sql
+
+import (
+	"context"
+	"database/sql/driver"
+	"errors"
+	"fmt"
+	"io"
+	"reflect"
+	"runtime"
+	"sort"
+	"strconv"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+var (
+	driversMu sync.RWMutex
+	drivers   = make(map[string]driver.Driver)
+)
+
+// nowFunc returns the current time; it's overridden in tests.
+var nowFunc = time.Now
+
+// Register makes a database driver available by the provided name.
+// If Register is called twice with the same name or if driver is nil,
+// it panics.
+func Register(name string, driver driver.Driver) {
+	driversMu.Lock()
+	defer driversMu.Unlock()
+	if driver == nil {
+		panic("sql: Register driver is nil")
+	}
+	if _, dup := drivers[name]; dup {
+		panic("sql: Register called twice for driver " + name)
+	}
+	drivers[name] = driver
+}
+
+func unregisterAllDrivers() {
+	driversMu.Lock()
+	defer driversMu.Unlock()
+	// For tests.
+	drivers = make(map[string]driver.Driver)
+}
+
+// Drivers returns a sorted list of the names of the registered drivers.
+func Drivers() []string {
+	driversMu.RLock()
+	defer driversMu.RUnlock()
+	list := make([]string, 0, len(drivers))
+	for name := range drivers {
+		list = append(list, name)
+	}
+	sort.Strings(list)
+	return list
+}
+
+// A NamedArg is a named argument. NamedArg values may be used as
+// arguments to Query or Exec and bind to the corresponding named
+// parameter in the SQL statement.
+//
+// For a more concise way to create NamedArg values, see
+// the Named function.
+type NamedArg struct {
+	_Named_Fields_Required struct{}
+
+	// Name is the name of the parameter placeholder.
+	//
+	// If empty, the ordinal position in the argument list will be
+	// used.
+	//
+	// Name must omit any symbol prefix.
+	Name string
+
+	// Value is the value of the parameter.
+	// It may be assigned the same value types as the query
+	// arguments.
+	Value interface{}
+}
+
+// Named provides a more concise way to create NamedArg values.
+//
+// Example usage:
+//
+//     db.ExecContext(ctx, `
+//         delete from Invoice
+//         where
+//             TimeCreated < @end
+//             and TimeCreated >= @start;`,
+//         sql.Named("start", startTime),
+//         sql.Named("end", endTime),
+//     )
+func Named(name string, value interface{}) NamedArg {
+	// This method exists because the go1compat promise
+	// doesn't guarantee that structs don't grow more fields,
+	// so unkeyed struct literals are a vet error. Thus, we don't
+	// want to allow sql.NamedArg{name, value}.
+	return NamedArg{Name: name, Value: value}
+}
+
+// IsolationLevel is the transaction isolation level used in TxOptions.
+type IsolationLevel int
+
+// Various isolation levels that drivers may support in BeginTx.
+// If a driver does not support a given isolation level an error may be returned.
+//
+// See https://en.wikipedia.org/wiki/Isolation_(database_systems)#Isolation_levels.
+const (
+	LevelDefault IsolationLevel = iota
+	LevelReadUncommitted
+	LevelReadCommitted
+	LevelWriteCommitted
+	LevelRepeatableRead
+	LevelSnapshot
+	LevelSerializable
+	LevelLinearizable
+)
+
+// String returns the name of the transaction isolation level.
+func (i IsolationLevel) String() string {
+	switch i {
+	case LevelDefault:
+		return "Default"
+	case LevelReadUncommitted:
+		return "Read Uncommitted"
+	case LevelReadCommitted:
+		return "Read Committed"
+	case LevelWriteCommitted:
+		return "Write Committed"
+	case LevelRepeatableRead:
+		return "Repeatable Read"
+	case LevelSnapshot:
+		return "Snapshot"
+	case LevelSerializable:
+		return "Serializable"
+	case LevelLinearizable:
+		return "Linearizable"
+	default:
+		return "IsolationLevel(" + strconv.Itoa(int(i)) + ")"
+	}
+}
+
+var _ fmt.Stringer = LevelDefault
+
+// TxOptions holds the transaction options to be used in DB.BeginTx.
+type TxOptions struct {
+	// Isolation is the transaction isolation level.
+	// If zero, the driver or database's default level is used.
+	Isolation IsolationLevel
+	ReadOnly  bool
+}
+
+// RawBytes is a byte slice that holds a reference to memory owned by
+// the database itself. After a Scan into a RawBytes, the slice is only
+// valid until the next call to Next, Scan, or Close.
+type RawBytes []byte
+
+// NullString represents a string that may be null.
+// NullString implements the Scanner interface so
+// it can be used as a scan destination:
+//
+//  var s NullString
+//  err := db.QueryRow("SELECT name FROM foo WHERE id=?", id).Scan(&s)
+//  ...
+//  if s.Valid {
+//     // use s.String
+//  } else {
+//     // NULL value
+//  }
+//
+type NullString struct {
+	String string
+	Valid  bool // Valid is true if String is not NULL
+}
+
+// Scan implements the Scanner interface.
+func (ns *NullString) Scan(value interface{}) error {
+	if value == nil {
+		ns.String, ns.Valid = "", false
+		return nil
+	}
+	ns.Valid = true
+	return convertAssign(&ns.String, value)
+}
+
+// Value implements the driver Valuer interface.
+func (ns NullString) Value() (driver.Value, error) {
+	if !ns.Valid {
+		return nil, nil
+	}
+	return ns.String, nil
+}
+
+// NullInt64 represents an int64 that may be null.
+// NullInt64 implements the Scanner interface so
+// it can be used as a scan destination, similar to NullString.
+type NullInt64 struct {
+	Int64 int64
+	Valid bool // Valid is true if Int64 is not NULL
+}
+
+// Scan implements the Scanner interface.
+func (n *NullInt64) Scan(value interface{}) error {
+	if value == nil {
+		n.Int64, n.Valid = 0, false
+		return nil
+	}
+	n.Valid = true
+	return convertAssign(&n.Int64, value)
+}
+
+// Value implements the driver Valuer interface.
+func (n NullInt64) Value() (driver.Value, error) {
+	if !n.Valid {
+		return nil, nil
+	}
+	return n.Int64, nil
+}
+
+// NullInt32 represents an int32 that may be null.
+// NullInt32 implements the Scanner interface so
+// it can be used as a scan destination, similar to NullString.
+type NullInt32 struct {
+	Int32 int32
+	Valid bool // Valid is true if Int32 is not NULL
+}
+
+// Scan implements the Scanner interface.
+func (n *NullInt32) Scan(value interface{}) error {
+	if value == nil {
+		n.Int32, n.Valid = 0, false
+		return nil
+	}
+	n.Valid = true
+	return convertAssign(&n.Int32, value)
+}
+
+// Value implements the driver Valuer interface.
+func (n NullInt32) Value() (driver.Value, error) {
+	if !n.Valid {
+		return nil, nil
+	}
+	return int64(n.Int32), nil
+}
+
+// NullFloat64 represents a float64 that may be null.
+// NullFloat64 implements the Scanner interface so
+// it can be used as a scan destination, similar to NullString.
+type NullFloat64 struct {
+	Float64 float64
+	Valid   bool // Valid is true if Float64 is not NULL
+}
+
+// Scan implements the Scanner interface.
+func (n *NullFloat64) Scan(value interface{}) error {
+	if value == nil {
+		n.Float64, n.Valid = 0, false
+		return nil
+	}
+	n.Valid = true
+	return convertAssign(&n.Float64, value)
+}
+
+// Value implements the driver Valuer interface.
+func (n NullFloat64) Value() (driver.Value, error) {
+	if !n.Valid {
+		return nil, nil
+	}
+	return n.Float64, nil
+}
+
+// NullBool represents a bool that may be null.
+// NullBool implements the Scanner interface so
+// it can be used as a scan destination, similar to NullString.
+type NullBool struct {
+	Bool  bool
+	Valid bool // Valid is true if Bool is not NULL
+}
+
+// Scan implements the Scanner interface.
+func (n *NullBool) Scan(value interface{}) error {
+	if value == nil {
+		n.Bool, n.Valid = false, false
+		return nil
+	}
+	n.Valid = true
+	return convertAssign(&n.Bool, value)
+}
+
+// Value implements the driver Valuer interface.
+func (n NullBool) Value() (driver.Value, error) {
+	if !n.Valid {
+		return nil, nil
+	}
+	return n.Bool, nil
+}
+
+// NullTime represents a time.Time that may be null.
+// NullTime implements the Scanner interface so
+// it can be used as a scan destination, similar to NullString.
+type NullTime struct {
+	Time  time.Time
+	Valid bool // Valid is true if Time is not NULL
+}
+
+// Scan implements the Scanner interface.
+func (n *NullTime) Scan(value interface{}) error {
+	if value == nil {
+		n.Time, n.Valid = time.Time{}, false
+		return nil
+	}
+	n.Valid = true
+	return convertAssign(&n.Time, value)
+}
+
+// Value implements the driver Valuer interface.
+func (n NullTime) Value() (driver.Value, error) {
+	if !n.Valid {
+		return nil, nil
+	}
+	return n.Time, nil
+}
+
+// Scanner is an interface used by Scan.
+type Scanner interface {
+	// Scan assigns a value from a database driver.
+	//
+	// The src value will be of one of the following types:
+	//
+	//    int64
+	//    float64
+	//    bool
+	//    []byte
+	//    string
+	//    time.Time
+	//    nil - for NULL values
+	//
+	// An error should be returned if the value cannot be stored
+	// without loss of information.
+	//
+	// Reference types such as []byte are only valid until the next call to Scan
+	// and should not be retained. Their underlying memory is owned by the driver.
+	// If retention is necessary, copy their values before the next call to Scan.
+	Scan(src interface{}) error
+}
+
+// Out may be used to retrieve OUTPUT value parameters from stored procedures.
+//
+// Not all drivers and databases support OUTPUT value parameters.
+//
+// Example usage:
+//
+//   var outArg string
+//   _, err := db.ExecContext(ctx, "ProcName", sql.Named("Arg1", sql.Out{Dest: &outArg}))
+type Out struct {
+	_Named_Fields_Required struct{}
+
+	// Dest is a pointer to the value that will be set to the result of the
+	// stored procedure's OUTPUT parameter.
+	Dest interface{}
+
+	// In is whether the parameter is an INOUT parameter. If so, the input value to the stored
+	// procedure is the dereferenced value of Dest's pointer, which is then replaced with
+	// the output value.
+	In bool
+}
+
+// ErrNoRows is returned by Scan when QueryRow doesn't return a
+// row. In such a case, QueryRow returns a placeholder *Row value that
+// defers this error until a Scan.
+var ErrNoRows = errors.New("sql: no rows in result set")
+
+// DB is a database handle representing a pool of zero or more
+// underlying connections. It's safe for concurrent use by multiple
+// goroutines.
+//
+// The sql package creates and frees connections automatically; it
+// also maintains a free pool of idle connections. If the database has
+// a concept of per-connection state, such state can be reliably observed
+// within a transaction (Tx) or connection (Conn). Once DB.Begin is called, the
+// returned Tx is bound to a single connection. Once Commit or
+// Rollback is called on the transaction, that transaction's
+// connection is returned to DB's idle connection pool. The pool size
+// can be controlled with SetMaxIdleConns.
+type DB struct {
+	// Atomic access only. At top of struct to prevent mis-alignment
+	// on 32-bit platforms. Of type time.Duration.
+	waitDuration int64 // Total time waited for new connections.
+
+	connector driver.Connector
+	// numClosed is an atomic counter which represents a total number of
+	// closed connections. Stmt.openStmt checks it before cleaning closed
+	// connections in Stmt.css.
+	numClosed uint64
+
+	mu           sync.Mutex // protects following fields
+	freeConn     []*driverConn
+	connRequests map[uint64]chan connRequest
+	nextRequest  uint64 // Next key to use in connRequests.
+	numOpen      int    // number of opened and pending open connections
+	// Used to signal the need for new connections
+	// a goroutine running connectionOpener() reads on this chan and
+	// maybeOpenNewConnections sends on the chan (one send per needed connection)
+	// It is closed during db.Close(). The close tells the connectionOpener
+	// goroutine to exit.
+	openerCh          chan struct{}
+	closed            bool
+	dep               map[finalCloser]depSet
+	lastPut           map[*driverConn]string // stacktrace of last conn's put; debug only
+	maxIdleCount      int                    // zero means defaultMaxIdleConns; negative means 0
+	maxOpen           int                    // <= 0 means unlimited
+	maxLifetime       time.Duration          // maximum amount of time a connection may be reused
+	maxIdleTime       time.Duration          // maximum amount of time a connection may be idle before being closed
+	cleanerCh         chan struct{}
+	waitCount         int64 // Total number of connections waited for.
+	maxIdleClosed     int64 // Total number of connections closed due to idle count.
+	maxIdleTimeClosed int64 // Total number of connections closed due to idle time.
+	maxLifetimeClosed int64 // Total number of connections closed due to max connection lifetime limit.
+
+	stop func() // stop cancels the connection opener.
+}
+
+// connReuseStrategy determines how (*DB).conn returns database connections.
+type connReuseStrategy uint8
+
+const (
+	// alwaysNewConn forces a new connection to the database.
+	alwaysNewConn connReuseStrategy = iota
+	// cachedOrNewConn returns a cached connection, if available, else waits
+	// for one to become available (if MaxOpenConns has been reached) or
+	// creates a new database connection.
+	cachedOrNewConn
+)
+
+// driverConn wraps a driver.Conn with a mutex, to
+// be held during all calls into the Conn. (including any calls onto
+// interfaces returned via that Conn, such as calls on Tx, Stmt,
+// Result, Rows)
+type driverConn struct {
+	db        *DB
+	createdAt time.Time
+
+	sync.Mutex  // guards following
+	ci          driver.Conn
+	needReset   bool // The connection session should be reset before use if true.
+	closed      bool
+	finalClosed bool // ci.Close has been called
+	openStmt    map[*driverStmt]bool
+
+	// guarded by db.mu
+	inUse      bool
+	returnedAt time.Time // Time the connection was created or returned.
+	onPut      []func()  // code (with db.mu held) run when conn is next returned
+	dbmuClosed bool      // same as closed, but guarded by db.mu, for removeClosedStmtLocked
+}
+
+func (dc *driverConn) releaseConn(err error) {
+	dc.db.putConn(dc, err, true)
+}
+
+func (dc *driverConn) removeOpenStmt(ds *driverStmt) {
+	dc.Lock()
+	defer dc.Unlock()
+	delete(dc.openStmt, ds)
+}
+
+func (dc *driverConn) expired(timeout time.Duration) bool {
+	if timeout <= 0 {
+		return false
+	}
+	return dc.createdAt.Add(timeout).Before(nowFunc())
+}
+
+// resetSession checks if the driver connection needs the
+// session to be reset and if required, resets it.
+func (dc *driverConn) resetSession(ctx context.Context) error {
+	dc.Lock()
+	defer dc.Unlock()
+
+	if !dc.needReset {
+		return nil
+	}
+	if cr, ok := dc.ci.(driver.SessionResetter); ok {
+		return cr.ResetSession(ctx)
+	}
+	return nil
+}
+
+// validateConnection checks if the connection is valid and can
+// still be used. It also marks the session for reset if required.
+func (dc *driverConn) validateConnection(needsReset bool) bool {
+	dc.Lock()
+	defer dc.Unlock()
+
+	if needsReset {
+		dc.needReset = true
+	}
+	if cv, ok := dc.ci.(driver.Validator); ok {
+		return cv.IsValid()
+	}
+	return true
+}
+
+// prepareLocked prepares the query on dc. When cg == nil the dc must keep track of
+// the prepared statements in a pool.
+func (dc *driverConn) prepareLocked(ctx context.Context, cg stmtConnGrabber, query string) (*driverStmt, error) {
+	si, err := ctxDriverPrepare(ctx, dc.ci, query)
+	if err != nil {
+		return nil, err
+	}
+	ds := &driverStmt{Locker: dc, si: si}
+
+	// No need to manage open statements if there is a single connection grabber.
+	if cg != nil {
+		return ds, nil
+	}
+
+	// Track each driverConn's open statements, so we can close them
+	// before closing the conn.
+	//
+	// Wrap all driver.Stmt is *driverStmt to ensure they are only closed once.
+	if dc.openStmt == nil {
+		dc.openStmt = make(map[*driverStmt]bool)
+	}
+	dc.openStmt[ds] = true
+	return ds, nil
+}
+
+// the dc.db's Mutex is held.
+func (dc *driverConn) closeDBLocked() func() error {
+	dc.Lock()
+	defer dc.Unlock()
+	if dc.closed {
+		return func() error { return errors.New("sql: duplicate driverConn close") }
+	}
+	dc.closed = true
+	return dc.db.removeDepLocked(dc, dc)
+}
+
+func (dc *driverConn) Close() error {
+	dc.Lock()
+	if dc.closed {
+		dc.Unlock()
+		return errors.New("sql: duplicate driverConn close")
+	}
+	dc.closed = true
+	dc.Unlock() // not defer; removeDep finalClose calls may need to lock
+
+	// And now updates that require holding dc.mu.Lock.
+	dc.db.mu.Lock()
+	dc.dbmuClosed = true
+	fn := dc.db.removeDepLocked(dc, dc)
+	dc.db.mu.Unlock()
+	return fn()
+}
+
+func (dc *driverConn) finalClose() error {
+	var err error
+
+	// Each *driverStmt has a lock to the dc. Copy the list out of the dc
+	// before calling close on each stmt.
+	var openStmt []*driverStmt
+	withLock(dc, func() {
+		openStmt = make([]*driverStmt, 0, len(dc.openStmt))
+		for ds := range dc.openStmt {
+			openStmt = append(openStmt, ds)
+		}
+		dc.openStmt = nil
+	})
+	for _, ds := range openStmt {
+		ds.Close()
+	}
+	withLock(dc, func() {
+		dc.finalClosed = true
+		err = dc.ci.Close()
+		dc.ci = nil
+	})
+
+	dc.db.mu.Lock()
+	dc.db.numOpen--
+	dc.db.maybeOpenNewConnections()
+	dc.db.mu.Unlock()
+
+	atomic.AddUint64(&dc.db.numClosed, 1)
+	return err
+}
+
+// driverStmt associates a driver.Stmt with the
+// *driverConn from which it came, so the driverConn's lock can be
+// held during calls.
+type driverStmt struct {
+	sync.Locker // the *driverConn
+	si          driver.Stmt
+	closed      bool
+	closeErr    error // return value of previous Close call
+}
+
+// Close ensures driver.Stmt is only closed once and always returns the same
+// result.
+func (ds *driverStmt) Close() error {
+	ds.Lock()
+	defer ds.Unlock()
+	if ds.closed {
+		return ds.closeErr
+	}
+	ds.closed = true
+	ds.closeErr = ds.si.Close()
+	return ds.closeErr
+}
+
+// depSet is a finalCloser's outstanding dependencies
+type depSet map[interface{}]bool // set of true bools
+
+// The finalCloser interface is used by (*DB).addDep and related
+// dependency reference counting.
+type finalCloser interface {
+	// finalClose is called when the reference count of an object
+	// goes to zero. (*DB).mu is not held while calling it.
+	finalClose() error
+}
+
+// addDep notes that x now depends on dep, and x's finalClose won't be
+// called until all of x's dependencies are removed with removeDep.
+func (db *DB) addDep(x finalCloser, dep interface{}) {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	db.addDepLocked(x, dep)
+}
+
+func (db *DB) addDepLocked(x finalCloser, dep interface{}) {
+	if db.dep == nil {
+		db.dep = make(map[finalCloser]depSet)
+	}
+	xdep := db.dep[x]
+	if xdep == nil {
+		xdep = make(depSet)
+		db.dep[x] = xdep
+	}
+	xdep[dep] = true
+}
+
+// removeDep notes that x no longer depends on dep.
+// If x still has dependencies, nil is returned.
+// If x no longer has any dependencies, its finalClose method will be
+// called and its error value will be returned.
+func (db *DB) removeDep(x finalCloser, dep interface{}) error {
+	db.mu.Lock()
+	fn := db.removeDepLocked(x, dep)
+	db.mu.Unlock()
+	return fn()
+}
+
+func (db *DB) removeDepLocked(x finalCloser, dep interface{}) func() error {
+
+	xdep, ok := db.dep[x]
+	if !ok {
+		panic(fmt.Sprintf("unpaired removeDep: no deps for %T", x))
+	}
+
+	l0 := len(xdep)
+	delete(xdep, dep)
+
+	switch len(xdep) {
+	case l0:
+		// Nothing removed. Shouldn't happen.
+		panic(fmt.Sprintf("unpaired removeDep: no %T dep on %T", dep, x))
+	case 0:
+		// No more dependencies.
+		delete(db.dep, x)
+		return x.finalClose
+	default:
+		// Dependencies remain.
+		return func() error { return nil }
+	}
+}
+
+// This is the size of the connectionOpener request chan (DB.openerCh).
+// This value should be larger than the maximum typical value
+// used for db.maxOpen. If maxOpen is significantly larger than
+// connectionRequestQueueSize then it is possible for ALL calls into the *DB
+// to block until the connectionOpener can satisfy the backlog of requests.
+var connectionRequestQueueSize = 1000000
+
+type dsnConnector struct {
+	dsn    string
+	driver driver.Driver
+}
+
+func (t dsnConnector) Connect(_ context.Context) (driver.Conn, error) {
+	return t.driver.Open(t.dsn)
+}
+
+func (t dsnConnector) Driver() driver.Driver {
+	return t.driver
+}
+
+// OpenDB opens a database using a Connector, allowing drivers to
+// bypass a string based data source name.
+//
+// Most users will open a database via a driver-specific connection
+// helper function that returns a *DB. No database drivers are included
+// in the Go standard library. See https://golang.org/s/sqldrivers for
+// a list of third-party drivers.
+//
+// OpenDB may just validate its arguments without creating a connection
+// to the database. To verify that the data source name is valid, call
+// Ping.
+//
+// The returned DB is safe for concurrent use by multiple goroutines
+// and maintains its own pool of idle connections. Thus, the OpenDB
+// function should be called just once. It is rarely necessary to
+// close a DB.
+func OpenDB(c driver.Connector) *DB {
+	ctx, cancel := context.WithCancel(context.Background())
+	db := &DB{
+		connector:    c,
+		openerCh:     make(chan struct{}, connectionRequestQueueSize),
+		lastPut:      make(map[*driverConn]string),
+		connRequests: make(map[uint64]chan connRequest),
+		stop:         cancel,
+	}
+
+	go db.connectionOpener(ctx)
+
+	return db
+}
+
+// Open opens a database specified by its database driver name and a
+// driver-specific data source name, usually consisting of at least a
+// database name and connection information.
+//
+// Most users will open a database via a driver-specific connection
+// helper function that returns a *DB. No database drivers are included
+// in the Go standard library. See https://golang.org/s/sqldrivers for
+// a list of third-party drivers.
+//
+// Open may just validate its arguments without creating a connection
+// to the database. To verify that the data source name is valid, call
+// Ping.
+//
+// The returned DB is safe for concurrent use by multiple goroutines
+// and maintains its own pool of idle connections. Thus, the Open
+// function should be called just once. It is rarely necessary to
+// close a DB.
+func Open(driverName, dataSourceName string) (*DB, error) {
+	driversMu.RLock()
+	driveri, ok := drivers[driverName]
+	driversMu.RUnlock()
+	if !ok {
+		return nil, fmt.Errorf("sql: unknown driver %q (forgotten import?)", driverName)
+	}
+
+	if driverCtx, ok := driveri.(driver.DriverContext); ok {
+		connector, err := driverCtx.OpenConnector(dataSourceName)
+		if err != nil {
+			return nil, err
+		}
+		return OpenDB(connector), nil
+	}
+
+	return OpenDB(dsnConnector{dsn: dataSourceName, driver: driveri}), nil
+}
+
+func (db *DB) pingDC(ctx context.Context, dc *driverConn, release func(error)) error {
+	var err error
+	if pinger, ok := dc.ci.(driver.Pinger); ok {
+		withLock(dc, func() {
+			err = pinger.Ping(ctx)
+		})
+	}
+	release(err)
+	return err
+}
+
+// PingContext verifies a connection to the database is still alive,
+// establishing a connection if necessary.
+func (db *DB) PingContext(ctx context.Context) error {
+	var dc *driverConn
+	var err error
+
+	for i := 0; i < maxBadConnRetries; i++ {
+		dc, err = db.conn(ctx, cachedOrNewConn)
+		if err != driver.ErrBadConn {
+			break
+		}
+	}
+	if err == driver.ErrBadConn {
+		dc, err = db.conn(ctx, alwaysNewConn)
+	}
+	if err != nil {
+		return err
+	}
+
+	return db.pingDC(ctx, dc, dc.releaseConn)
+}
+
+// Ping verifies a connection to the database is still alive,
+// establishing a connection if necessary.
+func (db *DB) Ping() error {
+	return db.PingContext(context.Background())
+}
+
+// Close closes the database and prevents new queries from starting.
+// Close then waits for all queries that have started processing on the server
+// to finish.
+//
+// It is rare to Close a DB, as the DB handle is meant to be
+// long-lived and shared between many goroutines.
+func (db *DB) Close() error {
+	db.mu.Lock()
+	if db.closed { // Make DB.Close idempotent
+		db.mu.Unlock()
+		return nil
+	}
+	if db.cleanerCh != nil {
+		close(db.cleanerCh)
+	}
+	var err error
+	fns := make([]func() error, 0, len(db.freeConn))
+	for _, dc := range db.freeConn {
+		fns = append(fns, dc.closeDBLocked())
+	}
+	db.freeConn = nil
+	db.closed = true
+	for _, req := range db.connRequests {
+		close(req)
+	}
+	db.mu.Unlock()
+	for _, fn := range fns {
+		err1 := fn()
+		if err1 != nil {
+			err = err1
+		}
+	}
+	db.stop()
+	return err
+}
+
+const defaultMaxIdleConns = 2
+
+func (db *DB) maxIdleConnsLocked() int {
+	n := db.maxIdleCount
+	switch {
+	case n == 0:
+		// TODO(bradfitz): ask driver, if supported, for its default preference
+		return defaultMaxIdleConns
+	case n < 0:
+		return 0
+	default:
+		return n
+	}
+}
+
+func (db *DB) shortestIdleTimeLocked() time.Duration {
+	if db.maxIdleTime <= 0 {
+		return db.maxLifetime
+	}
+	if db.maxLifetime <= 0 {
+		return db.maxIdleTime
+	}
+
+	min := db.maxIdleTime
+	if min > db.maxLifetime {
+		min = db.maxLifetime
+	}
+	return min
+}
+
+// SetMaxIdleConns sets the maximum number of connections in the idle
+// connection pool.
+//
+// If MaxOpenConns is greater than 0 but less than the new MaxIdleConns,
+// then the new MaxIdleConns will be reduced to match the MaxOpenConns limit.
+//
+// If n <= 0, no idle connections are retained.
+//
+// The default max idle connections is currently 2. This may change in
+// a future release.
+func (db *DB) SetMaxIdleConns(n int) {
+	db.mu.Lock()
+	if n > 0 {
+		db.maxIdleCount = n
+	} else {
+		// No idle connections.
+		db.maxIdleCount = -1
+	}
+	// Make sure maxIdle doesn't exceed maxOpen
+	if db.maxOpen > 0 && db.maxIdleConnsLocked() > db.maxOpen {
+		db.maxIdleCount = db.maxOpen
+	}
+	var closing []*driverConn
+	idleCount := len(db.freeConn)
+	maxIdle := db.maxIdleConnsLocked()
+	if idleCount > maxIdle {
+		closing = db.freeConn[maxIdle:]
+		db.freeConn = db.freeConn[:maxIdle]
+	}
+	db.maxIdleClosed += int64(len(closing))
+	db.mu.Unlock()
+	for _, c := range closing {
+		c.Close()
+	}
+}
+
+// SetMaxOpenConns sets the maximum number of open connections to the database.
+//
+// If MaxIdleConns is greater than 0 and the new MaxOpenConns is less than
+// MaxIdleConns, then MaxIdleConns will be reduced to match the new
+// MaxOpenConns limit.
+//
+// If n <= 0, then there is no limit on the number of open connections.
+// The default is 0 (unlimited).
+func (db *DB) SetMaxOpenConns(n int) {
+	db.mu.Lock()
+	db.maxOpen = n
+	if n < 0 {
+		db.maxOpen = 0
+	}
+	syncMaxIdle := db.maxOpen > 0 && db.maxIdleConnsLocked() > db.maxOpen
+	db.mu.Unlock()
+	if syncMaxIdle {
+		db.SetMaxIdleConns(n)
+	}
+}
+
+// SetConnMaxLifetime sets the maximum amount of time a connection may be reused.
+//
+// Expired connections may be closed lazily before reuse.
+//
+// If d <= 0, connections are not closed due to a connection's age.
+func (db *DB) SetConnMaxLifetime(d time.Duration) {
+	if d < 0 {
+		d = 0
+	}
+	db.mu.Lock()
+	// Wake cleaner up when lifetime is shortened.
+	if d > 0 && d < db.maxLifetime && db.cleanerCh != nil {
+		select {
+		case db.cleanerCh <- struct{}{}:
+		default:
+		}
+	}
+	db.maxLifetime = d
+	db.startCleanerLocked()
+	db.mu.Unlock()
+}
+
+// SetConnMaxIdleTime sets the maximum amount of time a connection may be idle.
+//
+// Expired connections may be closed lazily before reuse.
+//
+// If d <= 0, connections are not closed due to a connection's idle time.
+func (db *DB) SetConnMaxIdleTime(d time.Duration) {
+	if d < 0 {
+		d = 0
+	}
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	// Wake cleaner up when idle time is shortened.
+	if d > 0 && d < db.maxIdleTime && db.cleanerCh != nil {
+		select {
+		case db.cleanerCh <- struct{}{}:
+		default:
+		}
+	}
+	db.maxIdleTime = d
+	db.startCleanerLocked()
+}
+
+// startCleanerLocked starts connectionCleaner if needed.
+func (db *DB) startCleanerLocked() {
+	if (db.maxLifetime > 0 || db.maxIdleTime > 0) && db.numOpen > 0 && db.cleanerCh == nil {
+		db.cleanerCh = make(chan struct{}, 1)
+		go db.connectionCleaner(db.shortestIdleTimeLocked())
+	}
+}
+
+func (db *DB) connectionCleaner(d time.Duration) {
+	const minInterval = time.Second
+
+	if d < minInterval {
+		d = minInterval
+	}
+	t := time.NewTimer(d)
+
+	for {
+		select {
+		case <-t.C:
+		case <-db.cleanerCh: // maxLifetime was changed or db was closed.
+		}
+
+		db.mu.Lock()
+
+		d = db.shortestIdleTimeLocked()
+		if db.closed || db.numOpen == 0 || d <= 0 {
+			db.cleanerCh = nil
+			db.mu.Unlock()
+			return
+		}
+
+		closing := db.connectionCleanerRunLocked()
+		db.mu.Unlock()
+		for _, c := range closing {
+			c.Close()
+		}
+
+		if d < minInterval {
+			d = minInterval
+		}
+		t.Reset(d)
+	}
+}
+
+func (db *DB) connectionCleanerRunLocked() (closing []*driverConn) {
+	if db.maxLifetime > 0 {
+		expiredSince := nowFunc().Add(-db.maxLifetime)
+		for i := 0; i < len(db.freeConn); i++ {
+			c := db.freeConn[i]
+			if c.createdAt.Before(expiredSince) {
+				closing = append(closing, c)
+				last := len(db.freeConn) - 1
+				db.freeConn[i] = db.freeConn[last]
+				db.freeConn[last] = nil
+				db.freeConn = db.freeConn[:last]
+				i--
+			}
+		}
+		db.maxLifetimeClosed += int64(len(closing))
+	}
+
+	if db.maxIdleTime > 0 {
+		expiredSince := nowFunc().Add(-db.maxIdleTime)
+		var expiredCount int64
+		for i := 0; i < len(db.freeConn); i++ {
+			c := db.freeConn[i]
+			if db.maxIdleTime > 0 && c.returnedAt.Before(expiredSince) {
+				closing = append(closing, c)
+				expiredCount++
+				last := len(db.freeConn) - 1
+				db.freeConn[i] = db.freeConn[last]
+				db.freeConn[last] = nil
+				db.freeConn = db.freeConn[:last]
+				i--
+			}
+		}
+		db.maxIdleTimeClosed += expiredCount
+	}
+	return
+}
+
+// DBStats contains database statistics.
+type DBStats struct {
+	MaxOpenConnections int // Maximum number of open connections to the database.
+
+	// Pool Status
+	OpenConnections int // The number of established connections both in use and idle.
+	InUse           int // The number of connections currently in use.
+	Idle            int // The number of idle connections.
+
+	// Counters
+	WaitCount         int64         // The total number of connections waited for.
+	WaitDuration      time.Duration // The total time blocked waiting for a new connection.
+	MaxIdleClosed     int64         // The total number of connections closed due to SetMaxIdleConns.
+	MaxIdleTimeClosed int64         // The total number of connections closed due to SetConnMaxIdleTime.
+	MaxLifetimeClosed int64         // The total number of connections closed due to SetConnMaxLifetime.
+}
+
+// Stats returns database statistics.
+func (db *DB) Stats() DBStats {
+	wait := atomic.LoadInt64(&db.waitDuration)
+
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	stats := DBStats{
+		MaxOpenConnections: db.maxOpen,
+
+		Idle:            len(db.freeConn),
+		OpenConnections: db.numOpen,
+		InUse:           db.numOpen - len(db.freeConn),
+
+		WaitCount:         db.waitCount,
+		WaitDuration:      time.Duration(wait),
+		MaxIdleClosed:     db.maxIdleClosed,
+		MaxIdleTimeClosed: db.maxIdleTimeClosed,
+		MaxLifetimeClosed: db.maxLifetimeClosed,
+	}
+	return stats
+}
+
+// Assumes db.mu is locked.
+// If there are connRequests and the connection limit hasn't been reached,
+// then tell the connectionOpener to open new connections.
+func (db *DB) maybeOpenNewConnections() {
+	numRequests := len(db.connRequests)
+	if db.maxOpen > 0 {
+		numCanOpen := db.maxOpen - db.numOpen
+		if numRequests > numCanOpen {
+			numRequests = numCanOpen
+		}
+	}
+	for numRequests > 0 {
+		db.numOpen++ // optimistically
+		numRequests--
+		if db.closed {
+			return
+		}
+		db.openerCh <- struct{}{}
+	}
+}
+
+// Runs in a separate goroutine, opens new connections when requested.
+func (db *DB) connectionOpener(ctx context.Context) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-db.openerCh:
+			db.openNewConnection(ctx)
+		}
+	}
+}
+
+// Open one new connection
+func (db *DB) openNewConnection(ctx context.Context) {
+	// maybeOpenNewConnections has already executed db.numOpen++ before it sent
+	// on db.openerCh. This function must execute db.numOpen-- if the
+	// connection fails or is closed before returning.
+	ci, err := db.connector.Connect(ctx)
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	if db.closed {
+		if err == nil {
+			ci.Close()
+		}
+		db.numOpen--
+		return
+	}
+	if err != nil {
+		db.numOpen--
+		db.putConnDBLocked(nil, err)
+		db.maybeOpenNewConnections()
+		return
+	}
+	dc := &driverConn{
+		db:         db,
+		createdAt:  nowFunc(),
+		returnedAt: nowFunc(),
+		ci:         ci,
+	}
+	if db.putConnDBLocked(dc, err) {
+		db.addDepLocked(dc, dc)
+	} else {
+		db.numOpen--
+		ci.Close()
+	}
+}
+
+// connRequest represents one request for a new connection
+// When there are no idle connections available, DB.conn will create
+// a new connRequest and put it on the db.connRequests list.
+type connRequest struct {
+	conn *driverConn
+	err  error
+}
+
+var errDBClosed = errors.New("sql: database is closed")
+
+// nextRequestKeyLocked returns the next connection request key.
+// It is assumed that nextRequest will not overflow.
+func (db *DB) nextRequestKeyLocked() uint64 {
+	next := db.nextRequest
+	db.nextRequest++
+	return next
+}
+
+// conn returns a newly-opened or cached *driverConn.
+func (db *DB) conn(ctx context.Context, strategy connReuseStrategy) (*driverConn, error) {
+	db.mu.Lock()
+	if db.closed {
+		db.mu.Unlock()
+		return nil, errDBClosed
+	}
+	// Check if the context is expired.
+	select {
+	default:
+	case <-ctx.Done():
+		db.mu.Unlock()
+		return nil, ctx.Err()
+	}
+	lifetime := db.maxLifetime
+
+	// Prefer a free connection, if possible.
+	numFree := len(db.freeConn)
+	if strategy == cachedOrNewConn && numFree > 0 {
+		conn := db.freeConn[0]
+		copy(db.freeConn, db.freeConn[1:])
+		db.freeConn = db.freeConn[:numFree-1]
+		conn.inUse = true
+		if conn.expired(lifetime) {
+			db.maxLifetimeClosed++
+			db.mu.Unlock()
+			conn.Close()
+			return nil, driver.ErrBadConn
+		}
+		db.mu.Unlock()
+
+		// Reset the session if required.
+		if err := conn.resetSession(ctx); err == driver.ErrBadConn {
+			conn.Close()
+			return nil, driver.ErrBadConn
+		}
+
+		return conn, nil
+	}
+
+	// Out of free connections or we were asked not to use one. If we're not
+	// allowed to open any more connections, make a request and wait.
+	if db.maxOpen > 0 && db.numOpen >= db.maxOpen {
+		// Make the connRequest channel. It's buffered so that the
+		// connectionOpener doesn't block while waiting for the req to be read.
+		req := make(chan connRequest, 1)
+		reqKey := db.nextRequestKeyLocked()
+		db.connRequests[reqKey] = req
+		db.waitCount++
+		db.mu.Unlock()
+
+		waitStart := nowFunc()
+
+		// Timeout the connection request with the context.
+		select {
+		case <-ctx.Done():
+			// Remove the connection request and ensure no value has been sent
+			// on it after removing.
+			db.mu.Lock()
+			delete(db.connRequests, reqKey)
+			db.mu.Unlock()
+
+			atomic.AddInt64(&db.waitDuration, int64(time.Since(waitStart)))
+
+			select {
+			default:
+			case ret, ok := <-req:
+				if ok && ret.conn != nil {
+					db.putConn(ret.conn, ret.err, false)
+				}
+			}
+			return nil, ctx.Err()
+		case ret, ok := <-req:
+			atomic.AddInt64(&db.waitDuration, int64(time.Since(waitStart)))
+
+			if !ok {
+				return nil, errDBClosed
+			}
+			// Only check if the connection is expired if the strategy is cachedOrNewConns.
+			// If we require a new connection, just re-use the connection without looking
+			// at the expiry time. If it is expired, it will be checked when it is placed
+			// back into the connection pool.
+			// This prioritizes giving a valid connection to a client over the exact connection
+			// lifetime, which could expire exactly after this point anyway.
+			if strategy == cachedOrNewConn && ret.err == nil && ret.conn.expired(lifetime) {
+				db.mu.Lock()
+				db.maxLifetimeClosed++
+				db.mu.Unlock()
+				ret.conn.Close()
+				return nil, driver.ErrBadConn
+			}
+			if ret.conn == nil {
+				return nil, ret.err
+			}
+
+			// Reset the session if required.
+			if err := ret.conn.resetSession(ctx); err == driver.ErrBadConn {
+				ret.conn.Close()
+				return nil, driver.ErrBadConn
+			}
+			return ret.conn, ret.err
+		}
+	}
+
+	db.numOpen++ // optimistically
+	db.mu.Unlock()
+	ci, err := db.connector.Connect(ctx)
+	if err != nil {
+		db.mu.Lock()
+		db.numOpen-- // correct for earlier optimism
+		db.maybeOpenNewConnections()
+		db.mu.Unlock()
+		return nil, err
+	}
+	db.mu.Lock()
+	dc := &driverConn{
+		db:         db,
+		createdAt:  nowFunc(),
+		returnedAt: nowFunc(),
+		ci:         ci,
+		inUse:      true,
+	}
+	db.addDepLocked(dc, dc)
+	db.mu.Unlock()
+	return dc, nil
+}
+
+// putConnHook is a hook for testing.
+var putConnHook func(*DB, *driverConn)
+
+// noteUnusedDriverStatement notes that ds is no longer used and should
+// be closed whenever possible (when c is next not in use), unless c is
+// already closed.
+func (db *DB) noteUnusedDriverStatement(c *driverConn, ds *driverStmt) {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	if c.inUse {
+		c.onPut = append(c.onPut, func() {
+			ds.Close()
+		})
+	} else {
+		c.Lock()
+		fc := c.finalClosed
+		c.Unlock()
+		if !fc {
+			ds.Close()
+		}
+	}
+}
+
+// debugGetPut determines whether getConn & putConn calls' stack traces
+// are returned for more verbose crashes.
+const debugGetPut = false
+
+// putConn adds a connection to the db's free pool.
+// err is optionally the last error that occurred on this connection.
+func (db *DB) putConn(dc *driverConn, err error, resetSession bool) {
+	if err != driver.ErrBadConn {
+		if !dc.validateConnection(resetSession) {
+			err = driver.ErrBadConn
+		}
+	}
+	db.mu.Lock()
+	if !dc.inUse {
+		db.mu.Unlock()
+		if debugGetPut {
+			fmt.Printf("putConn(%v) DUPLICATE was: %s\n\nPREVIOUS was: %s", dc, stack(), db.lastPut[dc])
+		}
+		panic("sql: connection returned that was never out")
+	}
+
+	if err != driver.ErrBadConn && dc.expired(db.maxLifetime) {
+		db.maxLifetimeClosed++
+		err = driver.ErrBadConn
+	}
+	if debugGetPut {
+		db.lastPut[dc] = stack()
+	}
+	dc.inUse = false
+	dc.returnedAt = nowFunc()
+
+	for _, fn := range dc.onPut {
+		fn()
+	}
+	dc.onPut = nil
+
+	if err == driver.ErrBadConn {
+		// Don't reuse bad connections.
+		// Since the conn is considered bad and is being discarded, treat it
+		// as closed. Don't decrement the open count here, finalClose will
+		// take care of that.
+		db.maybeOpenNewConnections()
+		db.mu.Unlock()
+		dc.Close()
+		return
+	}
+	if putConnHook != nil {
+		putConnHook(db, dc)
+	}
+	added := db.putConnDBLocked(dc, nil)
+	db.mu.Unlock()
+
+	if !added {
+		dc.Close()
+		return
+	}
+}
+
+// Satisfy a connRequest or put the driverConn in the idle pool and return true
+// or return false.
+// putConnDBLocked will satisfy a connRequest if there is one, or it will
+// return the *driverConn to the freeConn list if err == nil and the idle
+// connection limit will not be exceeded.
+// If err != nil, the value of dc is ignored.
+// If err == nil, then dc must not equal nil.
+// If a connRequest was fulfilled or the *driverConn was placed in the
+// freeConn list, then true is returned, otherwise false is returned.
+func (db *DB) putConnDBLocked(dc *driverConn, err error) bool {
+	if db.closed {
+		return false
+	}
+	if db.maxOpen > 0 && db.numOpen > db.maxOpen {
+		return false
+	}
+	if c := len(db.connRequests); c > 0 {
+		var req chan connRequest
+		var reqKey uint64
+		for reqKey, req = range db.connRequests {
+			break
+		}
+		delete(db.connRequests, reqKey) // Remove from pending requests.
+		if err == nil {
+			dc.inUse = true
+		}
+		req <- connRequest{
+			conn: dc,
+			err:  err,
+		}
+		return true
+	} else if err == nil && !db.closed {
+		if db.maxIdleConnsLocked() > len(db.freeConn) {
+			db.freeConn = append(db.freeConn, dc)
+			db.startCleanerLocked()
+			return true
+		}
+		db.maxIdleClosed++
+	}
+	return false
+}
+
+// maxBadConnRetries is the number of maximum retries if the driver returns
+// driver.ErrBadConn to signal a broken connection before forcing a new
+// connection to be opened.
+const maxBadConnRetries = 2
+
+// PrepareContext creates a prepared statement for later queries or executions.
+// Multiple queries or executions may be run concurrently from the
+// returned statement.
+// The caller must call the statement's Close method
+// when the statement is no longer needed.
+//
+// The provided context is used for the preparation of the statement, not for the
+// execution of the statement.
+func (db *DB) PrepareContext(ctx context.Context, query string) (*Stmt, error) {
+	var stmt *Stmt
+	var err error
+	for i := 0; i < maxBadConnRetries; i++ {
+		stmt, err = db.prepare(ctx, query, cachedOrNewConn)
+		if err != driver.ErrBadConn {
+			break
+		}
+	}
+	if err == driver.ErrBadConn {
+		return db.prepare(ctx, query, alwaysNewConn)
+	}
+	return stmt, err
+}
+
+// Prepare creates a prepared statement for later queries or executions.
+// Multiple queries or executions may be run concurrently from the
+// returned statement.
+// The caller must call the statement's Close method
+// when the statement is no longer needed.
+func (db *DB) Prepare(query string) (*Stmt, error) {
+	return db.PrepareContext(context.Background(), query)
+}
+
+func (db *DB) prepare(ctx context.Context, query string, strategy connReuseStrategy) (*Stmt, error) {
+	// TODO: check if db.driver supports an optional
+	// driver.Preparer interface and call that instead, if so,
+	// otherwise we make a prepared statement that's bound
+	// to a connection, and to execute this prepared statement
+	// we either need to use this connection (if it's free), else
+	// get a new connection + re-prepare + execute on that one.
+	dc, err := db.conn(ctx, strategy)
+	if err != nil {
+		return nil, err
+	}
+	return db.prepareDC(ctx, dc, dc.releaseConn, nil, query)
+}
+
+// prepareDC prepares a query on the driverConn and calls release before
+// returning. When cg == nil it implies that a connection pool is used, and
+// when cg != nil only a single driver connection is used.
+func (db *DB) prepareDC(ctx context.Context, dc *driverConn, release func(error), cg stmtConnGrabber, query string) (*Stmt, error) {
+	var ds *driverStmt
+	var err error
+	defer func() {
+		release(err)
+	}()
+	withLock(dc, func() {
+		ds, err = dc.prepareLocked(ctx, cg, query)
+	})
+	if err != nil {
+		return nil, err
+	}
+	stmt := &Stmt{
+		db:    db,
+		query: query,
+		cg:    cg,
+		cgds:  ds,
+	}
+
+	// When cg == nil this statement will need to keep track of various
+	// connections they are prepared on and record the stmt dependency on
+	// the DB.
+	if cg == nil {
+		stmt.css = []connStmt{{dc, ds}}
+		stmt.lastNumClosed = atomic.LoadUint64(&db.numClosed)
+		db.addDep(stmt, stmt)
+	}
+	return stmt, nil
+}
+
+// ExecContext executes a query without returning any rows.
+// The args are for any placeholder parameters in the query.
+func (db *DB) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
+	var res Result
+	var err error
+	for i := 0; i < maxBadConnRetries; i++ {
+		res, err = db.exec(ctx, query, args, cachedOrNewConn)
+		if err != driver.ErrBadConn {
+			break
+		}
+	}
+	if err == driver.ErrBadConn {
+		return db.exec(ctx, query, args, alwaysNewConn)
+	}
+	return res, err
+}
+
+// Exec executes a query without returning any rows.
+// The args are for any placeholder parameters in the query.
+func (db *DB) Exec(query string, args ...interface{}) (Result, error) {
+	return db.ExecContext(context.Background(), query, args...)
+}
+
+func (db *DB) exec(ctx context.Context, query string, args []interface{}, strategy connReuseStrategy) (Result, error) {
+	dc, err := db.conn(ctx, strategy)
+	if err != nil {
+		return nil, err
+	}
+	return db.execDC(ctx, dc, dc.releaseConn, query, args)
+}
+
+func (db *DB) execDC(ctx context.Context, dc *driverConn, release func(error), query string, args []interface{}) (res Result, err error) {
+	defer func() {
+		release(err)
+	}()
+	execerCtx, ok := dc.ci.(driver.ExecerContext)
+	var execer driver.Execer
+	if !ok {
+		execer, ok = dc.ci.(driver.Execer)
+	}
+	if ok {
+		var nvdargs []driver.NamedValue
+		var resi driver.Result
+		withLock(dc, func() {
+			nvdargs, err = driverArgsConnLocked(dc.ci, nil, args)
+			if err != nil {
+				return
+			}
+			resi, err = ctxDriverExec(ctx, execerCtx, execer, query, nvdargs)
+		})
+		if err != driver.ErrSkip {
+			if err != nil {
+				return nil, err
+			}
+			return driverResult{dc, resi}, nil
+		}
+	}
+
+	var si driver.Stmt
+	withLock(dc, func() {
+		si, err = ctxDriverPrepare(ctx, dc.ci, query)
+	})
+	if err != nil {
+		return nil, err
+	}
+	ds := &driverStmt{Locker: dc, si: si}
+	defer ds.Close()
+	return resultFromStatement(ctx, dc.ci, ds, args...)
+}
+
+// QueryContext executes a query that returns rows, typically a SELECT.
+// The args are for any placeholder parameters in the query.
+func (db *DB) QueryContext(ctx context.Context, query string, args ...interface{}) (*Rows, error) {
+	var rows *Rows
+	var err error
+	for i := 0; i < maxBadConnRetries; i++ {
+		rows, err = db.query(ctx, query, args, cachedOrNewConn)
+		if err != driver.ErrBadConn {
+			break
+		}
+	}
+	if err == driver.ErrBadConn {
+		return db.query(ctx, query, args, alwaysNewConn)
+	}
+	return rows, err
+}
+
+// Query executes a query that returns rows, typically a SELECT.
+// The args are for any placeholder parameters in the query.
+func (db *DB) Query(query string, args ...interface{}) (*Rows, error) {
+	return db.QueryContext(context.Background(), query, args...)
+}
+
+func (db *DB) query(ctx context.Context, query string, args []interface{}, strategy connReuseStrategy) (*Rows, error) {
+	dc, err := db.conn(ctx, strategy)
+	if err != nil {
+		return nil, err
+	}
+
+	return db.queryDC(ctx, nil, dc, dc.releaseConn, query, args)
+}
+
+// queryDC executes a query on the given connection.
+// The connection gets released by the releaseConn function.
+// The ctx context is from a query method and the txctx context is from an
+// optional transaction context.
+func (db *DB) queryDC(ctx, txctx context.Context, dc *driverConn, releaseConn func(error), query string, args []interface{}) (*Rows, error) {
+	queryerCtx, ok := dc.ci.(driver.QueryerContext)
+	var queryer driver.Queryer
+	if !ok {
+		queryer, ok = dc.ci.(driver.Queryer)
+	}
+	if ok {
+		var nvdargs []driver.NamedValue
+		var rowsi driver.Rows
+		var err error
+		withLock(dc, func() {
+			nvdargs, err = driverArgsConnLocked(dc.ci, nil, args)
+			if err != nil {
+				return
+			}
+			rowsi, err = ctxDriverQuery(ctx, queryerCtx, queryer, query, nvdargs)
+		})
+		if err != driver.ErrSkip {
+			if err != nil {
+				releaseConn(err)
+				return nil, err
+			}
+			// Note: ownership of dc passes to the *Rows, to be freed
+			// with releaseConn.
+			rows := &Rows{
+				dc:          dc,
+				releaseConn: releaseConn,
+				rowsi:       rowsi,
+			}
+			rows.initContextClose(ctx, txctx)
+			return rows, nil
+		}
+	}
+
+	var si driver.Stmt
+	var err error
+	withLock(dc, func() {
+		si, err = ctxDriverPrepare(ctx, dc.ci, query)
+	})
+	if err != nil {
+		releaseConn(err)
+		return nil, err
+	}
+
+	ds := &driverStmt{Locker: dc, si: si}
+	rowsi, err := rowsiFromStatement(ctx, dc.ci, ds, args...)
+	if err != nil {
+		ds.Close()
+		releaseConn(err)
+		return nil, err
+	}
+
+	// Note: ownership of ci passes to the *Rows, to be freed
+	// with releaseConn.
+	rows := &Rows{
+		dc:          dc,
+		releaseConn: releaseConn,
+		rowsi:       rowsi,
+		closeStmt:   ds,
+	}
+	rows.initContextClose(ctx, txctx)
+	return rows, nil
+}
+
+// QueryRowContext executes a query that is expected to return at most one row.
+// QueryRowContext always returns a non-nil value. Errors are deferred until
+// Row's Scan method is called.
+// If the query selects no rows, the *Row's Scan will return ErrNoRows.
+// Otherwise, the *Row's Scan scans the first selected row and discards
+// the rest.
+func (db *DB) QueryRowContext(ctx context.Context, query string, args ...interface{}) *Row {
+	rows, err := db.QueryContext(ctx, query, args...)
+	return &Row{rows: rows, err: err}
+}
+
+// QueryRow executes a query that is expected to return at most one row.
+// QueryRow always returns a non-nil value. Errors are deferred until
+// Row's Scan method is called.
+// If the query selects no rows, the *Row's Scan will return ErrNoRows.
+// Otherwise, the *Row's Scan scans the first selected row and discards
+// the rest.
+func (db *DB) QueryRow(query string, args ...interface{}) *Row {
+	return db.QueryRowContext(context.Background(), query, args...)
+}
+
+// BeginTx starts a transaction.
+//
+// The provided context is used until the transaction is committed or rolled back.
+// If the context is canceled, the sql package will roll back
+// the transaction. Tx.Commit will return an error if the context provided to
+// BeginTx is canceled.
+//
+// The provided TxOptions is optional and may be nil if defaults should be used.
+// If a non-default isolation level is used that the driver doesn't support,
+// an error will be returned.
+func (db *DB) BeginTx(ctx context.Context, opts *TxOptions) (*Tx, error) {
+	var tx *Tx
+	var err error
+	for i := 0; i < maxBadConnRetries; i++ {
+		tx, err = db.begin(ctx, opts, cachedOrNewConn)
+		if err != driver.ErrBadConn {
+			break
+		}
+	}
+	if err == driver.ErrBadConn {
+		return db.begin(ctx, opts, alwaysNewConn)
+	}
+	return tx, err
+}
+
+// Begin starts a transaction. The default isolation level is dependent on
+// the driver.
+func (db *DB) Begin() (*Tx, error) {
+	return db.BeginTx(context.Background(), nil)
+}
+
+func (db *DB) begin(ctx context.Context, opts *TxOptions, strategy connReuseStrategy) (tx *Tx, err error) {
+	dc, err := db.conn(ctx, strategy)
+	if err != nil {
+		return nil, err
+	}
+	return db.beginDC(ctx, dc, dc.releaseConn, opts)
+}
+
+// beginDC starts a transaction. The provided dc must be valid and ready to use.
+func (db *DB) beginDC(ctx context.Context, dc *driverConn, release func(error), opts *TxOptions) (tx *Tx, err error) {
+	var txi driver.Tx
+	keepConnOnRollback := false
+	withLock(dc, func() {
+		_, hasSessionResetter := dc.ci.(driver.SessionResetter)
+		_, hasConnectionValidator := dc.ci.(driver.Validator)
+		keepConnOnRollback = hasSessionResetter && hasConnectionValidator
+		txi, err = ctxDriverBegin(ctx, opts, dc.ci)
+	})
+	if err != nil {
+		release(err)
+		return nil, err
+	}
+
+	// Schedule the transaction to rollback when the context is cancelled.
+	// The cancel function in Tx will be called after done is set to true.
+	ctx, cancel := context.WithCancel(ctx)
+	tx = &Tx{
+		db:                 db,
+		dc:                 dc,
+		releaseConn:        release,
+		txi:                txi,
+		cancel:             cancel,
+		keepConnOnRollback: keepConnOnRollback,
+		ctx:                ctx,
+	}
+	go tx.awaitDone()
+	return tx, nil
+}
+
+// Driver returns the database's underlying driver.
+func (db *DB) Driver() driver.Driver {
+	return db.connector.Driver()
+}
+
+// ErrConnDone is returned by any operation that is performed on a connection
+// that has already been returned to the connection pool.
+var ErrConnDone = errors.New("sql: connection is already closed")
+
+// Conn returns a single connection by either opening a new connection
+// or returning an existing connection from the connection pool. Conn will
+// block until either a connection is returned or ctx is canceled.
+// Queries run on the same Conn will be run in the same database session.
+//
+// Every Conn must be returned to the database pool after use by
+// calling Conn.Close.
+func (db *DB) Conn(ctx context.Context) (*Conn, error) {
+	var dc *driverConn
+	var err error
+	for i := 0; i < maxBadConnRetries; i++ {
+		dc, err = db.conn(ctx, cachedOrNewConn)
+		if err != driver.ErrBadConn {
+			break
+		}
+	}
+	if err == driver.ErrBadConn {
+		dc, err = db.conn(ctx, alwaysNewConn)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	conn := &Conn{
+		db: db,
+		dc: dc,
+	}
+	return conn, nil
+}
+
+type releaseConn func(error)
+
+// Conn represents a single database connection rather than a pool of database
+// connections. Prefer running queries from DB unless there is a specific
+// need for a continuous single database connection.
+//
+// A Conn must call Close to return the connection to the database pool
+// and may do so concurrently with a running query.
+//
+// After a call to Close, all operations on the
+// connection fail with ErrConnDone.
+type Conn struct {
+	db *DB
+
+	// closemu prevents the connection from closing while there
+	// is an active query. It is held for read during queries
+	// and exclusively during close.
+	closemu sync.RWMutex
+
+	// dc is owned until close, at which point
+	// it's returned to the connection pool.
+	dc *driverConn
+
+	// done transitions from 0 to 1 exactly once, on close.
+	// Once done, all operations fail with ErrConnDone.
+	// Use atomic operations on value when checking value.
+	done int32
+}
+
+// grabConn takes a context to implement stmtConnGrabber
+// but the context is not used.
+func (c *Conn) grabConn(context.Context) (*driverConn, releaseConn, error) {
+	if atomic.LoadInt32(&c.done) != 0 {
+		return nil, nil, ErrConnDone
+	}
+	c.closemu.RLock()
+	return c.dc, c.closemuRUnlockCondReleaseConn, nil
+}
+
+// PingContext verifies the connection to the database is still alive.
+func (c *Conn) PingContext(ctx context.Context) error {
+	dc, release, err := c.grabConn(ctx)
+	if err != nil {
+		return err
+	}
+	return c.db.pingDC(ctx, dc, release)
+}
+
+// ExecContext executes a query without returning any rows.
+// The args are for any placeholder parameters in the query.
+func (c *Conn) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
+	dc, release, err := c.grabConn(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return c.db.execDC(ctx, dc, release, query, args)
+}
+
+// QueryContext executes a query that returns rows, typically a SELECT.
+// The args are for any placeholder parameters in the query.
+func (c *Conn) QueryContext(ctx context.Context, query string, args ...interface{}) (*Rows, error) {
+	dc, release, err := c.grabConn(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return c.db.queryDC(ctx, nil, dc, release, query, args)
+}
+
+// QueryRowContext executes a query that is expected to return at most one row.
+// QueryRowContext always returns a non-nil value. Errors are deferred until
+// Row's Scan method is called.
+// If the query selects no rows, the *Row's Scan will return ErrNoRows.
+// Otherwise, the *Row's Scan scans the first selected row and discards
+// the rest.
+func (c *Conn) QueryRowContext(ctx context.Context, query string, args ...interface{}) *Row {
+	rows, err := c.QueryContext(ctx, query, args...)
+	return &Row{rows: rows, err: err}
+}
+
+// PrepareContext creates a prepared statement for later queries or executions.
+// Multiple queries or executions may be run concurrently from the
+// returned statement.
+// The caller must call the statement's Close method
+// when the statement is no longer needed.
+//
+// The provided context is used for the preparation of the statement, not for the
+// execution of the statement.
+func (c *Conn) PrepareContext(ctx context.Context, query string) (*Stmt, error) {
+	dc, release, err := c.grabConn(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return c.db.prepareDC(ctx, dc, release, c, query)
+}
+
+// Raw executes f exposing the underlying driver connection for the
+// duration of f. The driverConn must not be used outside of f.
+//
+// Once f returns and err is nil, the Conn will continue to be usable
+// until Conn.Close is called.
+func (c *Conn) Raw(f func(driverConn interface{}) error) (err error) {
+	var dc *driverConn
+	var release releaseConn
+
+	// grabConn takes a context to implement stmtConnGrabber, but the context is not used.
+	dc, release, err = c.grabConn(nil)
+	if err != nil {
+		return
+	}
+	fPanic := true
+	dc.Mutex.Lock()
+	defer func() {
+		dc.Mutex.Unlock()
+
+		// If f panics fPanic will remain true.
+		// Ensure an error is passed to release so the connection
+		// may be discarded.
+		if fPanic {
+			err = driver.ErrBadConn
+		}
+		release(err)
+	}()
+	err = f(dc.ci)
+	fPanic = false
+
+	return
+}
+
+// BeginTx starts a transaction.
+//
+// The provided context is used until the transaction is committed or rolled back.
+// If the context is canceled, the sql package will roll back
+// the transaction. Tx.Commit will return an error if the context provided to
+// BeginTx is canceled.
+//
+// The provided TxOptions is optional and may be nil if defaults should be used.
+// If a non-default isolation level is used that the driver doesn't support,
+// an error will be returned.
+func (c *Conn) BeginTx(ctx context.Context, opts *TxOptions) (*Tx, error) {
+	dc, release, err := c.grabConn(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return c.db.beginDC(ctx, dc, release, opts)
+}
+
+// closemuRUnlockCondReleaseConn read unlocks closemu
+// as the sql operation is done with the dc.
+func (c *Conn) closemuRUnlockCondReleaseConn(err error) {
+	c.closemu.RUnlock()
+	if err == driver.ErrBadConn {
+		c.close(err)
+	}
+}
+
+func (c *Conn) txCtx() context.Context {
+	return nil
+}
+
+func (c *Conn) close(err error) error {
+	if !atomic.CompareAndSwapInt32(&c.done, 0, 1) {
+		return ErrConnDone
+	}
+
+	// Lock around releasing the driver connection
+	// to ensure all queries have been stopped before doing so.
+	c.closemu.Lock()
+	defer c.closemu.Unlock()
+
+	c.dc.releaseConn(err)
+	c.dc = nil
+	c.db = nil
+	return err
+}
+
+// Close returns the connection to the connection pool.
+// All operations after a Close will return with ErrConnDone.
+// Close is safe to call concurrently with other operations and will
+// block until all other operations finish. It may be useful to first
+// cancel any used context and then call close directly after.
+func (c *Conn) Close() error {
+	return c.close(nil)
+}
+
+// Tx is an in-progress database transaction.
+//
+// A transaction must end with a call to Commit or Rollback.
+//
+// After a call to Commit or Rollback, all operations on the
+// transaction fail with ErrTxDone.
+//
+// The statements prepared for a transaction by calling
+// the transaction's Prepare or Stmt methods are closed
+// by the call to Commit or Rollback.
+type Tx struct {
+	db *DB
+
+	// closemu prevents the transaction from closing while there
+	// is an active query. It is held for read during queries
+	// and exclusively during close.
+	closemu sync.RWMutex
+
+	// dc is owned exclusively until Commit or Rollback, at which point
+	// it's returned with putConn.
+	dc  *driverConn
+	txi driver.Tx
+
+	// releaseConn is called once the Tx is closed to release
+	// any held driverConn back to the pool.
+	releaseConn func(error)
+
+	// done transitions from 0 to 1 exactly once, on Commit
+	// or Rollback. once done, all operations fail with
+	// ErrTxDone.
+	// Use atomic operations on value when checking value.
+	done int32
+
+	// keepConnOnRollback is true if the driver knows
+	// how to reset the connection's session and if need be discard
+	// the connection.
+	keepConnOnRollback bool
+
+	// All Stmts prepared for this transaction. These will be closed after the
+	// transaction has been committed or rolled back.
+	stmts struct {
+		sync.Mutex
+		v []*Stmt
+	}
+
+	// cancel is called after done transitions from 0 to 1.
+	cancel func()
+
+	// ctx lives for the life of the transaction.
+	ctx context.Context
+}
+
+// awaitDone blocks until the context in Tx is canceled and rolls back
+// the transaction if it's not already done.
+func (tx *Tx) awaitDone() {
+	// Wait for either the transaction to be committed or rolled
+	// back, or for the associated context to be closed.
+	<-tx.ctx.Done()
+
+	// Discard and close the connection used to ensure the
+	// transaction is closed and the resources are released.  This
+	// rollback does nothing if the transaction has already been
+	// committed or rolled back.
+	// Do not discard the connection if the connection knows
+	// how to reset the session.
+	discardConnection := !tx.keepConnOnRollback
+	tx.rollback(discardConnection)
+}
+
+func (tx *Tx) isDone() bool {
+	return atomic.LoadInt32(&tx.done) != 0
+}
+
+// ErrTxDone is returned by any operation that is performed on a transaction
+// that has already been committed or rolled back.
+var ErrTxDone = errors.New("sql: transaction has already been committed or rolled back")
+
+// close returns the connection to the pool and
+// must only be called by Tx.rollback or Tx.Commit while
+// tx is already canceled and won't be executed concurrently.
+func (tx *Tx) close(err error) {
+	tx.releaseConn(err)
+	tx.dc = nil
+	tx.txi = nil
+}
+
+// hookTxGrabConn specifies an optional hook to be called on
+// a successful call to (*Tx).grabConn. For tests.
+var hookTxGrabConn func()
+
+func (tx *Tx) grabConn(ctx context.Context) (*driverConn, releaseConn, error) {
+	select {
+	default:
+	case <-ctx.Done():
+		return nil, nil, ctx.Err()
+	}
+
+	// closemu.RLock must come before the check for isDone to prevent the Tx from
+	// closing while a query is executing.
+	tx.closemu.RLock()
+	if tx.isDone() {
+		tx.closemu.RUnlock()
+		return nil, nil, ErrTxDone
+	}
+	if hookTxGrabConn != nil { // test hook
+		hookTxGrabConn()
+	}
+	return tx.dc, tx.closemuRUnlockRelease, nil
+}
+
+func (tx *Tx) txCtx() context.Context {
+	return tx.ctx
+}
+
+// closemuRUnlockRelease is used as a func(error) method value in
+// ExecContext and QueryContext. Unlocking in the releaseConn keeps
+// the driver conn from being returned to the connection pool until
+// the Rows has been closed.
+func (tx *Tx) closemuRUnlockRelease(error) {
+	tx.closemu.RUnlock()
+}
+
+// Closes all Stmts prepared for this transaction.
+func (tx *Tx) closePrepared() {
+	tx.stmts.Lock()
+	defer tx.stmts.Unlock()
+	for _, stmt := range tx.stmts.v {
+		stmt.Close()
+	}
+}
+
+// Commit commits the transaction.
+func (tx *Tx) Commit() error {
+	// Check context first to avoid transaction leak.
+	// If put it behind tx.done CompareAndSwap statement, we can't ensure
+	// the consistency between tx.done and the real COMMIT operation.
+	select {
+	default:
+	case <-tx.ctx.Done():
+		if atomic.LoadInt32(&tx.done) == 1 {
+			return ErrTxDone
+		}
+		return tx.ctx.Err()
+	}
+	if !atomic.CompareAndSwapInt32(&tx.done, 0, 1) {
+		return ErrTxDone
+	}
+
+	// Cancel the Tx to release any active R-closemu locks.
+	// This is safe to do because tx.done has already transitioned
+	// from 0 to 1. Hold the W-closemu lock prior to rollback
+	// to ensure no other connection has an active query.
+	tx.cancel()
+	tx.closemu.Lock()
+	tx.closemu.Unlock()
+
+	var err error
+	withLock(tx.dc, func() {
+		err = tx.txi.Commit()
+	})
+	if err != driver.ErrBadConn {
+		tx.closePrepared()
+	}
+	tx.close(err)
+	return err
+}
+
+var rollbackHook func()
+
+// rollback aborts the transaction and optionally forces the pool to discard
+// the connection.
+func (tx *Tx) rollback(discardConn bool) error {
+	if !atomic.CompareAndSwapInt32(&tx.done, 0, 1) {
+		return ErrTxDone
+	}
+
+	if rollbackHook != nil {
+		rollbackHook()
+	}
+
+	// Cancel the Tx to release any active R-closemu locks.
+	// This is safe to do because tx.done has already transitioned
+	// from 0 to 1. Hold the W-closemu lock prior to rollback
+	// to ensure no other connection has an active query.
+	tx.cancel()
+	tx.closemu.Lock()
+	tx.closemu.Unlock()
+
+	var err error
+	withLock(tx.dc, func() {
+		err = tx.txi.Rollback()
+	})
+	if err != driver.ErrBadConn {
+		tx.closePrepared()
+	}
+	if discardConn {
+		err = driver.ErrBadConn
+	}
+	tx.close(err)
+	return err
+}
+
+// Rollback aborts the transaction.
+func (tx *Tx) Rollback() error {
+	return tx.rollback(false)
+}
+
+// PrepareContext creates a prepared statement for use within a transaction.
+//
+// The returned statement operates within the transaction and will be closed
+// when the transaction has been committed or rolled back.
+//
+// To use an existing prepared statement on this transaction, see Tx.Stmt.
+//
+// The provided context will be used for the preparation of the context, not
+// for the execution of the returned statement. The returned statement
+// will run in the transaction context.
+func (tx *Tx) PrepareContext(ctx context.Context, query string) (*Stmt, error) {
+	dc, release, err := tx.grabConn(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	stmt, err := tx.db.prepareDC(ctx, dc, release, tx, query)
+	if err != nil {
+		return nil, err
+	}
+	tx.stmts.Lock()
+	tx.stmts.v = append(tx.stmts.v, stmt)
+	tx.stmts.Unlock()
+	return stmt, nil
+}
+
+// Prepare creates a prepared statement for use within a transaction.
+//
+// The returned statement operates within the transaction and can no longer
+// be used once the transaction has been committed or rolled back.
+//
+// To use an existing prepared statement on this transaction, see Tx.Stmt.
+func (tx *Tx) Prepare(query string) (*Stmt, error) {
+	return tx.PrepareContext(context.Background(), query)
+}
+
+// StmtContext returns a transaction-specific prepared statement from
+// an existing statement.
+//
+// Example:
+//  updateMoney, err := db.Prepare("UPDATE balance SET money=money+? WHERE id=?")
+//  ...
+//  tx, err := db.Begin()
+//  ...
+//  res, err := tx.StmtContext(ctx, updateMoney).Exec(123.45, 98293203)
+//
+// The provided context is used for the preparation of the statement, not for the
+// execution of the statement.
+//
+// The returned statement operates within the transaction and will be closed
+// when the transaction has been committed or rolled back.
+func (tx *Tx) StmtContext(ctx context.Context, stmt *Stmt) *Stmt {
+	dc, release, err := tx.grabConn(ctx)
+	if err != nil {
+		return &Stmt{stickyErr: err}
+	}
+	defer release(nil)
+
+	if tx.db != stmt.db {
+		return &Stmt{stickyErr: errors.New("sql: Tx.Stmt: statement from different database used")}
+	}
+	var si driver.Stmt
+	var parentStmt *Stmt
+	stmt.mu.Lock()
+	if stmt.closed || stmt.cg != nil {
+		// If the statement has been closed or already belongs to a
+		// transaction, we can't reuse it in this connection.
+		// Since tx.StmtContext should never need to be called with a
+		// Stmt already belonging to tx, we ignore this edge case and
+		// re-prepare the statement in this case. No need to add
+		// code-complexity for this.
+		stmt.mu.Unlock()
+		withLock(dc, func() {
+			si, err = ctxDriverPrepare(ctx, dc.ci, stmt.query)
+		})
+		if err != nil {
+			return &Stmt{stickyErr: err}
+		}
+	} else {
+		stmt.removeClosedStmtLocked()
+		// See if the statement has already been prepared on this connection,
+		// and reuse it if possible.
+		for _, v := range stmt.css {
+			if v.dc == dc {
+				si = v.ds.si
+				break
+			}
+		}
+
+		stmt.mu.Unlock()
+
+		if si == nil {
+			var ds *driverStmt
+			withLock(dc, func() {
+				ds, err = stmt.prepareOnConnLocked(ctx, dc)
+			})
+			if err != nil {
+				return &Stmt{stickyErr: err}
+			}
+			si = ds.si
+		}
+		parentStmt = stmt
+	}
+
+	txs := &Stmt{
+		db: tx.db,
+		cg: tx,
+		cgds: &driverStmt{
+			Locker: dc,
+			si:     si,
+		},
+		parentStmt: parentStmt,
+		query:      stmt.query,
+	}
+	if parentStmt != nil {
+		tx.db.addDep(parentStmt, txs)
+	}
+	tx.stmts.Lock()
+	tx.stmts.v = append(tx.stmts.v, txs)
+	tx.stmts.Unlock()
+	return txs
+}
+
+// Stmt returns a transaction-specific prepared statement from
+// an existing statement.
+//
+// Example:
+//  updateMoney, err := db.Prepare("UPDATE balance SET money=money+? WHERE id=?")
+//  ...
+//  tx, err := db.Begin()
+//  ...
+//  res, err := tx.Stmt(updateMoney).Exec(123.45, 98293203)
+//
+// The returned statement operates within the transaction and will be closed
+// when the transaction has been committed or rolled back.
+func (tx *Tx) Stmt(stmt *Stmt) *Stmt {
+	return tx.StmtContext(context.Background(), stmt)
+}
+
+// ExecContext executes a query that doesn't return rows.
+// For example: an INSERT and UPDATE.
+func (tx *Tx) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
+	dc, release, err := tx.grabConn(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return tx.db.execDC(ctx, dc, release, query, args)
+}
+
+// Exec executes a query that doesn't return rows.
+// For example: an INSERT and UPDATE.
+func (tx *Tx) Exec(query string, args ...interface{}) (Result, error) {
+	return tx.ExecContext(context.Background(), query, args...)
+}
+
+// QueryContext executes a query that returns rows, typically a SELECT.
+func (tx *Tx) QueryContext(ctx context.Context, query string, args ...interface{}) (*Rows, error) {
+	dc, release, err := tx.grabConn(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	return tx.db.queryDC(ctx, tx.ctx, dc, release, query, args)
+}
+
+// Query executes a query that returns rows, typically a SELECT.
+func (tx *Tx) Query(query string, args ...interface{}) (*Rows, error) {
+	return tx.QueryContext(context.Background(), query, args...)
+}
+
+// QueryRowContext executes a query that is expected to return at most one row.
+// QueryRowContext always returns a non-nil value. Errors are deferred until
+// Row's Scan method is called.
+// If the query selects no rows, the *Row's Scan will return ErrNoRows.
+// Otherwise, the *Row's Scan scans the first selected row and discards
+// the rest.
+func (tx *Tx) QueryRowContext(ctx context.Context, query string, args ...interface{}) *Row {
+	rows, err := tx.QueryContext(ctx, query, args...)
+	return &Row{rows: rows, err: err}
+}
+
+// QueryRow executes a query that is expected to return at most one row.
+// QueryRow always returns a non-nil value. Errors are deferred until
+// Row's Scan method is called.
+// If the query selects no rows, the *Row's Scan will return ErrNoRows.
+// Otherwise, the *Row's Scan scans the first selected row and discards
+// the rest.
+func (tx *Tx) QueryRow(query string, args ...interface{}) *Row {
+	return tx.QueryRowContext(context.Background(), query, args...)
+}
+
+// connStmt is a prepared statement on a particular connection.
+type connStmt struct {
+	dc *driverConn
+	ds *driverStmt
+}
+
+// stmtConnGrabber represents a Tx or Conn that will return the underlying
+// driverConn and release function.
+type stmtConnGrabber interface {
+	// grabConn returns the driverConn and the associated release function
+	// that must be called when the operation completes.
+	grabConn(context.Context) (*driverConn, releaseConn, error)
+
+	// txCtx returns the transaction context if available.
+	// The returned context should be selected on along with
+	// any query context when awaiting a cancel.
+	txCtx() context.Context
+}
+
+var (
+	_ stmtConnGrabber = &Tx{}
+	_ stmtConnGrabber = &Conn{}
+)
+
+// Stmt is a prepared statement.
+// A Stmt is safe for concurrent use by multiple goroutines.
+//
+// If a Stmt is prepared on a Tx or Conn, it will be bound to a single
+// underlying connection forever. If the Tx or Conn closes, the Stmt will
+// become unusable and all operations will return an error.
+// If a Stmt is prepared on a DB, it will remain usable for the lifetime of the
+// DB. When the Stmt needs to execute on a new underlying connection, it will
+// prepare itself on the new connection automatically.
+type Stmt struct {
+	// Immutable:
+	db        *DB    // where we came from
+	query     string // that created the Stmt
+	stickyErr error  // if non-nil, this error is returned for all operations
+
+	closemu sync.RWMutex // held exclusively during close, for read otherwise.
+
+	// If Stmt is prepared on a Tx or Conn then cg is present and will
+	// only ever grab a connection from cg.
+	// If cg is nil then the Stmt must grab an arbitrary connection
+	// from db and determine if it must prepare the stmt again by
+	// inspecting css.
+	cg   stmtConnGrabber
+	cgds *driverStmt
+
+	// parentStmt is set when a transaction-specific statement
+	// is requested from an identical statement prepared on the same
+	// conn. parentStmt is used to track the dependency of this statement
+	// on its originating ("parent") statement so that parentStmt may
+	// be closed by the user without them having to know whether or not
+	// any transactions are still using it.
+	parentStmt *Stmt
+
+	mu     sync.Mutex // protects the rest of the fields
+	closed bool
+
+	// css is a list of underlying driver statement interfaces
+	// that are valid on particular connections. This is only
+	// used if cg == nil and one is found that has idle
+	// connections. If cg != nil, cgds is always used.
+	css []connStmt
+
+	// lastNumClosed is copied from db.numClosed when Stmt is created
+	// without tx and closed connections in css are removed.
+	lastNumClosed uint64
+}
+
+// ExecContext executes a prepared statement with the given arguments and
+// returns a Result summarizing the effect of the statement.
+func (s *Stmt) ExecContext(ctx context.Context, args ...interface{}) (Result, error) {
+	s.closemu.RLock()
+	defer s.closemu.RUnlock()
+
+	var res Result
+	strategy := cachedOrNewConn
+	for i := 0; i < maxBadConnRetries+1; i++ {
+		if i == maxBadConnRetries {
+			strategy = alwaysNewConn
+		}
+		dc, releaseConn, ds, err := s.connStmt(ctx, strategy)
+		if err != nil {
+			if err == driver.ErrBadConn {
+				continue
+			}
+			return nil, err
+		}
+
+		res, err = resultFromStatement(ctx, dc.ci, ds, args...)
+		releaseConn(err)
+		if err != driver.ErrBadConn {
+			return res, err
+		}
+	}
+	return nil, driver.ErrBadConn
+}
+
+// Exec executes a prepared statement with the given arguments and
+// returns a Result summarizing the effect of the statement.
+func (s *Stmt) Exec(args ...interface{}) (Result, error) {
+	return s.ExecContext(context.Background(), args...)
+}
+
+func resultFromStatement(ctx context.Context, ci driver.Conn, ds *driverStmt, args ...interface{}) (Result, error) {
+	ds.Lock()
+	defer ds.Unlock()
+
+	dargs, err := driverArgsConnLocked(ci, ds, args)
+	if err != nil {
+		return nil, err
+	}
+
+	resi, err := ctxDriverStmtExec(ctx, ds.si, dargs)
+	if err != nil {
+		return nil, err
+	}
+	return driverResult{ds.Locker, resi}, nil
+}
+
+// removeClosedStmtLocked removes closed conns in s.css.
+//
+// To avoid lock contention on DB.mu, we do it only when
+// s.db.numClosed - s.lastNum is large enough.
+func (s *Stmt) removeClosedStmtLocked() {
+	t := len(s.css)/2 + 1
+	if t > 10 {
+		t = 10
+	}
+	dbClosed := atomic.LoadUint64(&s.db.numClosed)
+	if dbClosed-s.lastNumClosed < uint64(t) {
+		return
+	}
+
+	s.db.mu.Lock()
+	for i := 0; i < len(s.css); i++ {
+		if s.css[i].dc.dbmuClosed {
+			s.css[i] = s.css[len(s.css)-1]
+			s.css = s.css[:len(s.css)-1]
+			i--
+		}
+	}
+	s.db.mu.Unlock()
+	s.lastNumClosed = dbClosed
+}
+
+// connStmt returns a free driver connection on which to execute the
+// statement, a function to call to release the connection, and a
+// statement bound to that connection.
+func (s *Stmt) connStmt(ctx context.Context, strategy connReuseStrategy) (dc *driverConn, releaseConn func(error), ds *driverStmt, err error) {
+	if err = s.stickyErr; err != nil {
+		return
+	}
+	s.mu.Lock()
+	if s.closed {
+		s.mu.Unlock()
+		err = errors.New("sql: statement is closed")
+		return
+	}
+
+	// In a transaction or connection, we always use the connection that the
+	// stmt was created on.
+	if s.cg != nil {
+		s.mu.Unlock()
+		dc, releaseConn, err = s.cg.grabConn(ctx) // blocks, waiting for the connection.
+		if err != nil {
+			return
+		}
+		return dc, releaseConn, s.cgds, nil
+	}
+
+	s.removeClosedStmtLocked()
+	s.mu.Unlock()
+
+	dc, err = s.db.conn(ctx, strategy)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	s.mu.Lock()
+	for _, v := range s.css {
+		if v.dc == dc {
+			s.mu.Unlock()
+			return dc, dc.releaseConn, v.ds, nil
+		}
+	}
+	s.mu.Unlock()
+
+	// No luck; we need to prepare the statement on this connection
+	withLock(dc, func() {
+		ds, err = s.prepareOnConnLocked(ctx, dc)
+	})
+	if err != nil {
+		dc.releaseConn(err)
+		return nil, nil, nil, err
+	}
+
+	return dc, dc.releaseConn, ds, nil
+}
+
+// prepareOnConnLocked prepares the query in Stmt s on dc and adds it to the list of
+// open connStmt on the statement. It assumes the caller is holding the lock on dc.
+func (s *Stmt) prepareOnConnLocked(ctx context.Context, dc *driverConn) (*driverStmt, error) {
+	si, err := dc.prepareLocked(ctx, s.cg, s.query)
+	if err != nil {
+		return nil, err
+	}
+	cs := connStmt{dc, si}
+	s.mu.Lock()
+	s.css = append(s.css, cs)
+	s.mu.Unlock()
+	return cs.ds, nil
+}
+
+// QueryContext executes a prepared query statement with the given arguments
+// and returns the query results as a *Rows.
+func (s *Stmt) QueryContext(ctx context.Context, args ...interface{}) (*Rows, error) {
+	s.closemu.RLock()
+	defer s.closemu.RUnlock()
+
+	var rowsi driver.Rows
+	strategy := cachedOrNewConn
+	for i := 0; i < maxBadConnRetries+1; i++ {
+		if i == maxBadConnRetries {
+			strategy = alwaysNewConn
+		}
+		dc, releaseConn, ds, err := s.connStmt(ctx, strategy)
+		if err != nil {
+			if err == driver.ErrBadConn {
+				continue
+			}
+			return nil, err
+		}
+
+		rowsi, err = rowsiFromStatement(ctx, dc.ci, ds, args...)
+		if err == nil {
+			// Note: ownership of ci passes to the *Rows, to be freed
+			// with releaseConn.
+			rows := &Rows{
+				dc:    dc,
+				rowsi: rowsi,
+				// releaseConn set below
+			}
+			// addDep must be added before initContextClose or it could attempt
+			// to removeDep before it has been added.
+			s.db.addDep(s, rows)
+
+			// releaseConn must be set before initContextClose or it could
+			// release the connection before it is set.
+			rows.releaseConn = func(err error) {
+				releaseConn(err)
+				s.db.removeDep(s, rows)
+			}
+			var txctx context.Context
+			if s.cg != nil {
+				txctx = s.cg.txCtx()
+			}
+			rows.initContextClose(ctx, txctx)
+			return rows, nil
+		}
+
+		releaseConn(err)
+		if err != driver.ErrBadConn {
+			return nil, err
+		}
+	}
+	return nil, driver.ErrBadConn
+}
+
+// Query executes a prepared query statement with the given arguments
+// and returns the query results as a *Rows.
+func (s *Stmt) Query(args ...interface{}) (*Rows, error) {
+	return s.QueryContext(context.Background(), args...)
+}
+
+func rowsiFromStatement(ctx context.Context, ci driver.Conn, ds *driverStmt, args ...interface{}) (driver.Rows, error) {
+	ds.Lock()
+	defer ds.Unlock()
+	dargs, err := driverArgsConnLocked(ci, ds, args)
+	if err != nil {
+		return nil, err
+	}
+	return ctxDriverStmtQuery(ctx, ds.si, dargs)
+}
+
+// QueryRowContext executes a prepared query statement with the given arguments.
+// If an error occurs during the execution of the statement, that error will
+// be returned by a call to Scan on the returned *Row, which is always non-nil.
+// If the query selects no rows, the *Row's Scan will return ErrNoRows.
+// Otherwise, the *Row's Scan scans the first selected row and discards
+// the rest.
+func (s *Stmt) QueryRowContext(ctx context.Context, args ...interface{}) *Row {
+	rows, err := s.QueryContext(ctx, args...)
+	if err != nil {
+		return &Row{err: err}
+	}
+	return &Row{rows: rows}
+}
+
+// QueryRow executes a prepared query statement with the given arguments.
+// If an error occurs during the execution of the statement, that error will
+// be returned by a call to Scan on the returned *Row, which is always non-nil.
+// If the query selects no rows, the *Row's Scan will return ErrNoRows.
+// Otherwise, the *Row's Scan scans the first selected row and discards
+// the rest.
+//
+// Example usage:
+//
+//  var name string
+//  err := nameByUseridStmt.QueryRow(id).Scan(&name)
+func (s *Stmt) QueryRow(args ...interface{}) *Row {
+	return s.QueryRowContext(context.Background(), args...)
+}
+
+// Close closes the statement.
+func (s *Stmt) Close() error {
+	s.closemu.Lock()
+	defer s.closemu.Unlock()
+
+	if s.stickyErr != nil {
+		return s.stickyErr
+	}
+	s.mu.Lock()
+	if s.closed {
+		s.mu.Unlock()
+		return nil
+	}
+	s.closed = true
+	txds := s.cgds
+	s.cgds = nil
+
+	s.mu.Unlock()
+
+	if s.cg == nil {
+		return s.db.removeDep(s, s)
+	}
+
+	if s.parentStmt != nil {
+		// If parentStmt is set, we must not close s.txds since it's stored
+		// in the css array of the parentStmt.
+		return s.db.removeDep(s.parentStmt, s)
+	}
+	return txds.Close()
+}
+
+func (s *Stmt) finalClose() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.css != nil {
+		for _, v := range s.css {
+			s.db.noteUnusedDriverStatement(v.dc, v.ds)
+			v.dc.removeOpenStmt(v.ds)
+		}
+		s.css = nil
+	}
+	return nil
+}
+
+// Rows is the result of a query. Its cursor starts before the first row
+// of the result set. Use Next to advance from row to row.
+type Rows struct {
+	dc          *driverConn // owned; must call releaseConn when closed to release
+	releaseConn func(error)
+	rowsi       driver.Rows
+	cancel      func()      // called when Rows is closed, may be nil.
+	closeStmt   *driverStmt // if non-nil, statement to Close on close
+
+	// closemu prevents Rows from closing while there
+	// is an active streaming result. It is held for read during non-close operations
+	// and exclusively during close.
+	//
+	// closemu guards lasterr and closed.
+	closemu sync.RWMutex
+	closed  bool
+	lasterr error // non-nil only if closed is true
+
+	// lastcols is only used in Scan, Next, and NextResultSet which are expected
+	// not to be called concurrently.
+	lastcols []driver.Value
+}
+
+// lasterrOrErrLocked returns either lasterr or the provided err.
+// rs.closemu must be read-locked.
+func (rs *Rows) lasterrOrErrLocked(err error) error {
+	if rs.lasterr != nil && rs.lasterr != io.EOF {
+		return rs.lasterr
+	}
+	return err
+}
+
+// bypassRowsAwaitDone is only used for testing.
+// If true, it will not close the Rows automatically from the context.
+var bypassRowsAwaitDone = false
+
+func (rs *Rows) initContextClose(ctx, txctx context.Context) {
+	if ctx.Done() == nil && (txctx == nil || txctx.Done() == nil) {
+		return
+	}
+	if bypassRowsAwaitDone {
+		return
+	}
+	ctx, rs.cancel = context.WithCancel(ctx)
+	go rs.awaitDone(ctx, txctx)
+}
+
+// awaitDone blocks until either ctx or txctx is canceled. The ctx is provided
+// from the query context and is canceled when the query Rows is closed.
+// If the query was issued in a transaction, the transaction's context
+// is also provided in txctx to ensure Rows is closed if the Tx is closed.
+func (rs *Rows) awaitDone(ctx, txctx context.Context) {
+	var txctxDone <-chan struct{}
+	if txctx != nil {
+		txctxDone = txctx.Done()
+	}
+	select {
+	case <-ctx.Done():
+	case <-txctxDone:
+	}
+	rs.close(ctx.Err())
+}
+
+// Next prepares the next result row for reading with the Scan method. It
+// returns true on success, or false if there is no next result row or an error
+// happened while preparing it. Err should be consulted to distinguish between
+// the two cases.
+//
+// Every call to Scan, even the first one, must be preceded by a call to Next.
+func (rs *Rows) Next() bool {
+	var doClose, ok bool
+	withLock(rs.closemu.RLocker(), func() {
+		doClose, ok = rs.nextLocked()
+	})
+	if doClose {
+		rs.Close()
+	}
+	return ok
+}
+
+func (rs *Rows) nextLocked() (doClose, ok bool) {
+	if rs.closed {
+		return false, false
+	}
+
+	// Lock the driver connection before calling the driver interface
+	// rowsi to prevent a Tx from rolling back the connection at the same time.
+	rs.dc.Lock()
+	defer rs.dc.Unlock()
+
+	if rs.lastcols == nil {
+		rs.lastcols = make([]driver.Value, len(rs.rowsi.Columns()))
+	}
+
+	rs.lasterr = rs.rowsi.Next(rs.lastcols)
+	if rs.lasterr != nil {
+		// Close the connection if there is a driver error.
+		if rs.lasterr != io.EOF {
+			return true, false
+		}
+		nextResultSet, ok := rs.rowsi.(driver.RowsNextResultSet)
+		if !ok {
+			return true, false
+		}
+		// The driver is at the end of the current result set.
+		// Test to see if there is another result set after the current one.
+		// Only close Rows if there is no further result sets to read.
+		if !nextResultSet.HasNextResultSet() {
+			doClose = true
+		}
+		return doClose, false
+	}
+	return false, true
+}
+
+// NextResultSet prepares the next result set for reading. It reports whether
+// there is further result sets, or false if there is no further result set
+// or if there is an error advancing to it. The Err method should be consulted
+// to distinguish between the two cases.
+//
+// After calling NextResultSet, the Next method should always be called before
+// scanning. If there are further result sets they may not have rows in the result
+// set.
+func (rs *Rows) NextResultSet() bool {
+	var doClose bool
+	defer func() {
+		if doClose {
+			rs.Close()
+		}
+	}()
+	rs.closemu.RLock()
+	defer rs.closemu.RUnlock()
+
+	if rs.closed {
+		return false
+	}
+
+	rs.lastcols = nil
+	nextResultSet, ok := rs.rowsi.(driver.RowsNextResultSet)
+	if !ok {
+		doClose = true
+		return false
+	}
+
+	// Lock the driver connection before calling the driver interface
+	// rowsi to prevent a Tx from rolling back the connection at the same time.
+	rs.dc.Lock()
+	defer rs.dc.Unlock()
+
+	rs.lasterr = nextResultSet.NextResultSet()
+	if rs.lasterr != nil {
+		doClose = true
+		return false
+	}
+	return true
+}
+
+// Err returns the error, if any, that was encountered during iteration.
+// Err may be called after an explicit or implicit Close.
+func (rs *Rows) Err() error {
+	rs.closemu.RLock()
+	defer rs.closemu.RUnlock()
+	return rs.lasterrOrErrLocked(nil)
+}
+
+var errRowsClosed = errors.New("sql: Rows are closed")
+var errNoRows = errors.New("sql: no Rows available")
+
+// Columns returns the column names.
+// Columns returns an error if the rows are closed.
+func (rs *Rows) Columns() ([]string, error) {
+	rs.closemu.RLock()
+	defer rs.closemu.RUnlock()
+	if rs.closed {
+		return nil, rs.lasterrOrErrLocked(errRowsClosed)
+	}
+	if rs.rowsi == nil {
+		return nil, rs.lasterrOrErrLocked(errNoRows)
+	}
+	rs.dc.Lock()
+	defer rs.dc.Unlock()
+
+	return rs.rowsi.Columns(), nil
+}
+
+// ColumnTypes returns column information such as column type, length,
+// and nullable. Some information may not be available from some drivers.
+func (rs *Rows) ColumnTypes() ([]*ColumnType, error) {
+	rs.closemu.RLock()
+	defer rs.closemu.RUnlock()
+	if rs.closed {
+		return nil, rs.lasterrOrErrLocked(errRowsClosed)
+	}
+	if rs.rowsi == nil {
+		return nil, rs.lasterrOrErrLocked(errNoRows)
+	}
+	rs.dc.Lock()
+	defer rs.dc.Unlock()
+
+	return rowsColumnInfoSetupConnLocked(rs.rowsi), nil
+}
+
+// ColumnType contains the name and type of a column.
+type ColumnType struct {
+	name string
+
+	hasNullable       bool
+	hasLength         bool
+	hasPrecisionScale bool
+
+	nullable     bool
+	length       int64
+	databaseType string
+	precision    int64
+	scale        int64
+	scanType     reflect.Type
+}
+
+// Name returns the name or alias of the column.
+func (ci *ColumnType) Name() string {
+	return ci.name
+}
+
+// Length returns the column type length for variable length column types such
+// as text and binary field types. If the type length is unbounded the value will
+// be math.MaxInt64 (any database limits will still apply).
+// If the column type is not variable length, such as an int, or if not supported
+// by the driver ok is false.
+func (ci *ColumnType) Length() (length int64, ok bool) {
+	return ci.length, ci.hasLength
+}
+
+// DecimalSize returns the scale and precision of a decimal type.
+// If not applicable or if not supported ok is false.
+func (ci *ColumnType) DecimalSize() (precision, scale int64, ok bool) {
+	return ci.precision, ci.scale, ci.hasPrecisionScale
+}
+
+// ScanType returns a Go type suitable for scanning into using Rows.Scan.
+// If a driver does not support this property ScanType will return
+// the type of an empty interface.
+func (ci *ColumnType) ScanType() reflect.Type {
+	return ci.scanType
+}
+
+// Nullable reports whether the column may be null.
+// If a driver does not support this property ok will be false.
+func (ci *ColumnType) Nullable() (nullable, ok bool) {
+	return ci.nullable, ci.hasNullable
+}
+
+// DatabaseTypeName returns the database system name of the column type. If an empty
+// string is returned, then the driver type name is not supported.
+// Consult your driver documentation for a list of driver data types. Length specifiers
+// are not included.
+// Common type names include "VARCHAR", "TEXT", "NVARCHAR", "DECIMAL", "BOOL",
+// "INT", and "BIGINT".
+func (ci *ColumnType) DatabaseTypeName() string {
+	return ci.databaseType
+}
+
+func rowsColumnInfoSetupConnLocked(rowsi driver.Rows) []*ColumnType {
+	names := rowsi.Columns()
+
+	list := make([]*ColumnType, len(names))
+	for i := range list {
+		ci := &ColumnType{
+			name: names[i],
+		}
+		list[i] = ci
+
+		if prop, ok := rowsi.(driver.RowsColumnTypeScanType); ok {
+			ci.scanType = prop.ColumnTypeScanType(i)
+		} else {
+			ci.scanType = reflect.TypeOf(new(interface{})).Elem()
+		}
+		if prop, ok := rowsi.(driver.RowsColumnTypeDatabaseTypeName); ok {
+			ci.databaseType = prop.ColumnTypeDatabaseTypeName(i)
+		}
+		if prop, ok := rowsi.(driver.RowsColumnTypeLength); ok {
+			ci.length, ci.hasLength = prop.ColumnTypeLength(i)
+		}
+		if prop, ok := rowsi.(driver.RowsColumnTypeNullable); ok {
+			ci.nullable, ci.hasNullable = prop.ColumnTypeNullable(i)
+		}
+		if prop, ok := rowsi.(driver.RowsColumnTypePrecisionScale); ok {
+			ci.precision, ci.scale, ci.hasPrecisionScale = prop.ColumnTypePrecisionScale(i)
+		}
+	}
+	return list
+}
+
+// Scan copies the columns in the current row into the values pointed
+// at by dest. The number of values in dest must be the same as the
+// number of columns in Rows.
+//
+// Scan converts columns read from the database into the following
+// common Go types and special types provided by the sql package:
+//
+//    *string
+//    *[]byte
+//    *int, *int8, *int16, *int32, *int64
+//    *uint, *uint8, *uint16, *uint32, *uint64
+//    *bool
+//    *float32, *float64
+//    *interface{}
+//    *RawBytes
+//    *Rows (cursor value)
+//    any type implementing Scanner (see Scanner docs)
+//
+// In the most simple case, if the type of the value from the source
+// column is an integer, bool or string type T and dest is of type *T,
+// Scan simply assigns the value through the pointer.
+//
+// Scan also converts between string and numeric types, as long as no
+// information would be lost. While Scan stringifies all numbers
+// scanned from numeric database columns into *string, scans into
+// numeric types are checked for overflow. For example, a float64 with
+// value 300 or a string with value "300" can scan into a uint16, but
+// not into a uint8, though float64(255) or "255" can scan into a
+// uint8. One exception is that scans of some float64 numbers to
+// strings may lose information when stringifying. In general, scan
+// floating point columns into *float64.
+//
+// If a dest argument has type *[]byte, Scan saves in that argument a
+// copy of the corresponding data. The copy is owned by the caller and
+// can be modified and held indefinitely. The copy can be avoided by
+// using an argument of type *RawBytes instead; see the documentation
+// for RawBytes for restrictions on its use.
+//
+// If an argument has type *interface{}, Scan copies the value
+// provided by the underlying driver without conversion. When scanning
+// from a source value of type []byte to *interface{}, a copy of the
+// slice is made and the caller owns the result.
+//
+// Source values of type time.Time may be scanned into values of type
+// *time.Time, *interface{}, *string, or *[]byte. When converting to
+// the latter two, time.RFC3339Nano is used.
+//
+// Source values of type bool may be scanned into types *bool,
+// *interface{}, *string, *[]byte, or *RawBytes.
+//
+// For scanning into *bool, the source may be true, false, 1, 0, or
+// string inputs parseable by strconv.ParseBool.
+//
+// Scan can also convert a cursor returned from a query, such as
+// "select cursor(select * from my_table) from dual", into a
+// *Rows value that can itself be scanned from. The parent
+// select query will close any cursor *Rows if the parent *Rows is closed.
+//
+// If any of the first arguments implementing Scanner returns an error,
+// that error will be wrapped in the returned error
+func (rs *Rows) Scan(dest ...interface{}) error {
+	rs.closemu.RLock()
+
+	if rs.lasterr != nil && rs.lasterr != io.EOF {
+		rs.closemu.RUnlock()
+		return rs.lasterr
+	}
+	if rs.closed {
+		err := rs.lasterrOrErrLocked(errRowsClosed)
+		rs.closemu.RUnlock()
+		return err
+	}
+	rs.closemu.RUnlock()
+
+	if rs.lastcols == nil {
+		return errors.New("sql: Scan called without calling Next")
+	}
+	if len(dest) != len(rs.lastcols) {
+		return fmt.Errorf("sql: expected %d destination arguments in Scan, not %d", len(rs.lastcols), len(dest))
+	}
+	for i, sv := range rs.lastcols {
+		err := convertAssignRows(dest[i], sv, rs)
+		if err != nil {
+			return fmt.Errorf(`sql: Scan error on column index %d, name %q: %w`, i, rs.rowsi.Columns()[i], err)
+		}
+	}
+	return nil
+}
+
+// rowsCloseHook returns a function so tests may install the
+// hook through a test only mutex.
+var rowsCloseHook = func() func(*Rows, *error) { return nil }
+
+// Close closes the Rows, preventing further enumeration. If Next is called
+// and returns false and there are no further result sets,
+// the Rows are closed automatically and it will suffice to check the
+// result of Err. Close is idempotent and does not affect the result of Err.
+func (rs *Rows) Close() error {
+	return rs.close(nil)
+}
+
+func (rs *Rows) close(err error) error {
+	rs.closemu.Lock()
+	defer rs.closemu.Unlock()
+
+	if rs.closed {
+		return nil
+	}
+	rs.closed = true
+
+	if rs.lasterr == nil {
+		rs.lasterr = err
+	}
+
+	withLock(rs.dc, func() {
+		err = rs.rowsi.Close()
+	})
+	if fn := rowsCloseHook(); fn != nil {
+		fn(rs, &err)
+	}
+	if rs.cancel != nil {
+		rs.cancel()
+	}
+
+	if rs.closeStmt != nil {
+		rs.closeStmt.Close()
+	}
+	rs.releaseConn(err)
+	return err
+}
+
+// Row is the result of calling QueryRow to select a single row.
+type Row struct {
+	// One of these two will be non-nil:
+	err  error // deferred error for easy chaining
+	rows *Rows
+}
+
+// Scan copies the columns from the matched row into the values
+// pointed at by dest. See the documentation on Rows.Scan for details.
+// If more than one row matches the query,
+// Scan uses the first row and discards the rest. If no row matches
+// the query, Scan returns ErrNoRows.
+func (r *Row) Scan(dest ...interface{}) error {
+	if r.err != nil {
+		return r.err
+	}
+
+	// TODO(bradfitz): for now we need to defensively clone all
+	// []byte that the driver returned (not permitting
+	// *RawBytes in Rows.Scan), since we're about to close
+	// the Rows in our defer, when we return from this function.
+	// the contract with the driver.Next(...) interface is that it
+	// can return slices into read-only temporary memory that's
+	// only valid until the next Scan/Close. But the TODO is that
+	// for a lot of drivers, this copy will be unnecessary. We
+	// should provide an optional interface for drivers to
+	// implement to say, "don't worry, the []bytes that I return
+	// from Next will not be modified again." (for instance, if
+	// they were obtained from the network anyway) But for now we
+	// don't care.
+	defer r.rows.Close()
+	for _, dp := range dest {
+		if _, ok := dp.(*RawBytes); ok {
+			return errors.New("sql: RawBytes isn't allowed on Row.Scan")
+		}
+	}
+
+	if !r.rows.Next() {
+		if err := r.rows.Err(); err != nil {
+			return err
+		}
+		return ErrNoRows
+	}
+	err := r.rows.Scan(dest...)
+	if err != nil {
+		return err
+	}
+	// Make sure the query can be processed to completion with no errors.
+	return r.rows.Close()
+}
+
+// Err provides a way for wrapping packages to check for
+// query errors without calling Scan.
+// Err returns the error, if any, that was encountered while running the query.
+// If this error is not nil, this error will also be returned from Scan.
+func (r *Row) Err() error {
+	return r.err
+}
+
+// A Result summarizes an executed SQL command.
+type Result interface {
+	// LastInsertId returns the integer generated by the database
+	// in response to a command. Typically this will be from an
+	// "auto increment" column when inserting a new row. Not all
+	// databases support this feature, and the syntax of such
+	// statements varies.
+	LastInsertId() (int64, error)
+
+	// RowsAffected returns the number of rows affected by an
+	// update, insert, or delete. Not every database or database
+	// driver may support this.
+	RowsAffected() (int64, error)
+}
+
+type driverResult struct {
+	sync.Locker // the *driverConn
+	resi        driver.Result
+}
+
+func (dr driverResult) LastInsertId() (int64, error) {
+	dr.Lock()
+	defer dr.Unlock()
+	return dr.resi.LastInsertId()
+}
+
+func (dr driverResult) RowsAffected() (int64, error) {
+	dr.Lock()
+	defer dr.Unlock()
+	return dr.resi.RowsAffected()
+}
+
+func stack() string {
+	var buf [2 << 10]byte
+	return string(buf[:runtime.Stack(buf[:], false)])
+}
+
+// withLock runs while holding lk.
+func withLock(lk sync.Locker, fn func()) {
+	lk.Lock()
+	defer lk.Unlock() // in case fn panics
+	fn()
+}
diff --git a/src/database/sql/sql_test.go b/src/database/sql/sql_test.go
new file mode 100644
index 0000000..c968852
--- /dev/null
+++ b/src/database/sql/sql_test.go
@@ -0,0 +1,4424 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sql
+
+import (
+	"context"
+	"database/sql/driver"
+	"errors"
+	"fmt"
+	"math/rand"
+	"reflect"
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func init() {
+	type dbConn struct {
+		db *DB
+		c  *driverConn
+	}
+	freedFrom := make(map[dbConn]string)
+	var mu sync.Mutex
+	getFreedFrom := func(c dbConn) string {
+		mu.Lock()
+		defer mu.Unlock()
+		return freedFrom[c]
+	}
+	setFreedFrom := func(c dbConn, s string) {
+		mu.Lock()
+		defer mu.Unlock()
+		freedFrom[c] = s
+	}
+	putConnHook = func(db *DB, c *driverConn) {
+		idx := -1
+		for i, v := range db.freeConn {
+			if v == c {
+				idx = i
+				break
+			}
+		}
+		if idx >= 0 {
+			// print before panic, as panic may get lost due to conflicting panic
+			// (all goroutines asleep) elsewhere, since we might not unlock
+			// the mutex in freeConn here.
+			println("double free of conn. conflicts are:\nA) " + getFreedFrom(dbConn{db, c}) + "\n\nand\nB) " + stack())
+			panic("double free of conn.")
+		}
+		setFreedFrom(dbConn{db, c}, stack())
+	}
+}
+
+const fakeDBName = "foo"
+
+var chrisBirthday = time.Unix(123456789, 0)
+
+func newTestDB(t testing.TB, name string) *DB {
+	return newTestDBConnector(t, &fakeConnector{name: fakeDBName}, name)
+}
+
+func newTestDBConnector(t testing.TB, fc *fakeConnector, name string) *DB {
+	fc.name = fakeDBName
+	db := OpenDB(fc)
+	if _, err := db.Exec("WIPE"); err != nil {
+		t.Fatalf("exec wipe: %v", err)
+	}
+	if name == "people" {
+		exec(t, db, "CREATE|people|name=string,age=int32,photo=blob,dead=bool,bdate=datetime")
+		exec(t, db, "INSERT|people|name=Alice,age=?,photo=APHOTO", 1)
+		exec(t, db, "INSERT|people|name=Bob,age=?,photo=BPHOTO", 2)
+		exec(t, db, "INSERT|people|name=Chris,age=?,photo=CPHOTO,bdate=?", 3, chrisBirthday)
+	}
+	if name == "magicquery" {
+		// Magic table name and column, known by fakedb_test.go.
+		exec(t, db, "CREATE|magicquery|op=string,millis=int32")
+		exec(t, db, "INSERT|magicquery|op=sleep,millis=10")
+	}
+	if name == "tx_status" {
+		// Magic table name and column, known by fakedb_test.go.
+		exec(t, db, "CREATE|tx_status|tx_status=string")
+		exec(t, db, "INSERT|tx_status|tx_status=invalid")
+	}
+	return db
+}
+
+func TestOpenDB(t *testing.T) {
+	db := OpenDB(dsnConnector{dsn: fakeDBName, driver: fdriver})
+	if db.Driver() != fdriver {
+		t.Fatalf("OpenDB should return the driver of the Connector")
+	}
+}
+
+func TestDriverPanic(t *testing.T) {
+	// Test that if driver panics, database/sql does not deadlock.
+	db, err := Open("test", fakeDBName)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	expectPanic := func(name string, f func()) {
+		defer func() {
+			err := recover()
+			if err == nil {
+				t.Fatalf("%s did not panic", name)
+			}
+		}()
+		f()
+	}
+
+	expectPanic("Exec Exec", func() { db.Exec("PANIC|Exec|WIPE") })
+	exec(t, db, "WIPE") // check not deadlocked
+	expectPanic("Exec NumInput", func() { db.Exec("PANIC|NumInput|WIPE") })
+	exec(t, db, "WIPE") // check not deadlocked
+	expectPanic("Exec Close", func() { db.Exec("PANIC|Close|WIPE") })
+	exec(t, db, "WIPE")             // check not deadlocked
+	exec(t, db, "PANIC|Query|WIPE") // should run successfully: Exec does not call Query
+	exec(t, db, "WIPE")             // check not deadlocked
+
+	exec(t, db, "CREATE|people|name=string,age=int32,photo=blob,dead=bool,bdate=datetime")
+
+	expectPanic("Query Query", func() { db.Query("PANIC|Query|SELECT|people|age,name|") })
+	expectPanic("Query NumInput", func() { db.Query("PANIC|NumInput|SELECT|people|age,name|") })
+	expectPanic("Query Close", func() {
+		rows, err := db.Query("PANIC|Close|SELECT|people|age,name|")
+		if err != nil {
+			t.Fatal(err)
+		}
+		rows.Close()
+	})
+	db.Query("PANIC|Exec|SELECT|people|age,name|") // should run successfully: Query does not call Exec
+	exec(t, db, "WIPE")                            // check not deadlocked
+}
+
+func exec(t testing.TB, db *DB, query string, args ...interface{}) {
+	t.Helper()
+	_, err := db.Exec(query, args...)
+	if err != nil {
+		t.Fatalf("Exec of %q: %v", query, err)
+	}
+}
+
+func closeDB(t testing.TB, db *DB) {
+	if e := recover(); e != nil {
+		fmt.Printf("Panic: %v\n", e)
+		panic(e)
+	}
+	defer setHookpostCloseConn(nil)
+	setHookpostCloseConn(func(_ *fakeConn, err error) {
+		if err != nil {
+			t.Errorf("Error closing fakeConn: %v", err)
+		}
+	})
+	db.mu.Lock()
+	for i, dc := range db.freeConn {
+		if n := len(dc.openStmt); n > 0 {
+			// Just a sanity check. This is legal in
+			// general, but if we make the tests clean up
+			// their statements first, then we can safely
+			// verify this is always zero here, and any
+			// other value is a leak.
+			t.Errorf("while closing db, freeConn %d/%d had %d open stmts; want 0", i, len(db.freeConn), n)
+		}
+	}
+	db.mu.Unlock()
+
+	err := db.Close()
+	if err != nil {
+		t.Fatalf("error closing DB: %v", err)
+	}
+
+	var numOpen int
+	if !waitCondition(5*time.Second, 5*time.Millisecond, func() bool {
+		numOpen = db.numOpenConns()
+		return numOpen == 0
+	}) {
+		t.Fatalf("%d connections still open after closing DB", numOpen)
+	}
+}
+
+// numPrepares assumes that db has exactly 1 idle conn and returns
+// its count of calls to Prepare
+func numPrepares(t *testing.T, db *DB) int {
+	if n := len(db.freeConn); n != 1 {
+		t.Fatalf("free conns = %d; want 1", n)
+	}
+	return db.freeConn[0].ci.(*fakeConn).numPrepare
+}
+
+func (db *DB) numDeps() int {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	return len(db.dep)
+}
+
+// Dependencies are closed via a goroutine, so this polls waiting for
+// numDeps to fall to want, waiting up to d.
+func (db *DB) numDepsPollUntil(want int, d time.Duration) int {
+	deadline := time.Now().Add(d)
+	for {
+		n := db.numDeps()
+		if n <= want || time.Now().After(deadline) {
+			return n
+		}
+		time.Sleep(50 * time.Millisecond)
+	}
+}
+
+func (db *DB) numFreeConns() int {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	return len(db.freeConn)
+}
+
+func (db *DB) numOpenConns() int {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	return db.numOpen
+}
+
+// clearAllConns closes all connections in db.
+func (db *DB) clearAllConns(t *testing.T) {
+	db.SetMaxIdleConns(0)
+
+	if g, w := db.numFreeConns(), 0; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	if n := db.numDepsPollUntil(0, time.Second); n > 0 {
+		t.Errorf("number of dependencies = %d; expected 0", n)
+		db.dumpDeps(t)
+	}
+}
+
+func (db *DB) dumpDeps(t *testing.T) {
+	for fc := range db.dep {
+		db.dumpDep(t, 0, fc, map[finalCloser]bool{})
+	}
+}
+
+func (db *DB) dumpDep(t *testing.T, depth int, dep finalCloser, seen map[finalCloser]bool) {
+	seen[dep] = true
+	indent := strings.Repeat("  ", depth)
+	ds := db.dep[dep]
+	for k := range ds {
+		t.Logf("%s%T (%p) waiting for -> %T (%p)", indent, dep, dep, k, k)
+		if fc, ok := k.(finalCloser); ok {
+			if !seen[fc] {
+				db.dumpDep(t, depth+1, fc, seen)
+			}
+		}
+	}
+}
+
+func TestQuery(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	prepares0 := numPrepares(t, db)
+	rows, err := db.Query("SELECT|people|age,name|")
+	if err != nil {
+		t.Fatalf("Query: %v", err)
+	}
+	type row struct {
+		age  int
+		name string
+	}
+	got := []row{}
+	for rows.Next() {
+		var r row
+		err = rows.Scan(&r.age, &r.name)
+		if err != nil {
+			t.Fatalf("Scan: %v", err)
+		}
+		got = append(got, r)
+	}
+	err = rows.Err()
+	if err != nil {
+		t.Fatalf("Err: %v", err)
+	}
+	want := []row{
+		{age: 1, name: "Alice"},
+		{age: 2, name: "Bob"},
+		{age: 3, name: "Chris"},
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("mismatch.\n got: %#v\nwant: %#v", got, want)
+	}
+
+	// And verify that the final rows.Next() call, which hit EOF,
+	// also closed the rows connection.
+	if n := db.numFreeConns(); n != 1 {
+		t.Fatalf("free conns after query hitting EOF = %d; want 1", n)
+	}
+	if prepares := numPrepares(t, db) - prepares0; prepares != 1 {
+		t.Errorf("executed %d Prepare statements; want 1", prepares)
+	}
+}
+
+// TestQueryContext tests canceling the context while scanning the rows.
+func TestQueryContext(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	prepares0 := numPrepares(t, db)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	rows, err := db.QueryContext(ctx, "SELECT|people|age,name|")
+	if err != nil {
+		t.Fatalf("Query: %v", err)
+	}
+	type row struct {
+		age  int
+		name string
+	}
+	got := []row{}
+	index := 0
+	for rows.Next() {
+		if index == 2 {
+			cancel()
+			waitForRowsClose(t, rows, 5*time.Second)
+		}
+		var r row
+		err = rows.Scan(&r.age, &r.name)
+		if err != nil {
+			if index == 2 {
+				break
+			}
+			t.Fatalf("Scan: %v", err)
+		}
+		if index == 2 && err != context.Canceled {
+			t.Fatalf("Scan: %v; want context.Canceled", err)
+		}
+		got = append(got, r)
+		index++
+	}
+	select {
+	case <-ctx.Done():
+		if err := ctx.Err(); err != context.Canceled {
+			t.Fatalf("context err = %v; want context.Canceled", err)
+		}
+	default:
+		t.Fatalf("context err = nil; want context.Canceled")
+	}
+	want := []row{
+		{age: 1, name: "Alice"},
+		{age: 2, name: "Bob"},
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("mismatch.\n got: %#v\nwant: %#v", got, want)
+	}
+
+	// And verify that the final rows.Next() call, which hit EOF,
+	// also closed the rows connection.
+	waitForRowsClose(t, rows, 5*time.Second)
+	waitForFree(t, db, 5*time.Second, 1)
+	if prepares := numPrepares(t, db) - prepares0; prepares != 1 {
+		t.Errorf("executed %d Prepare statements; want 1", prepares)
+	}
+}
+
+func waitCondition(waitFor, checkEvery time.Duration, fn func() bool) bool {
+	deadline := time.Now().Add(waitFor)
+	for time.Now().Before(deadline) {
+		if fn() {
+			return true
+		}
+		time.Sleep(checkEvery)
+	}
+	return false
+}
+
+// waitForFree checks db.numFreeConns until either it equals want or
+// the maxWait time elapses.
+func waitForFree(t *testing.T, db *DB, maxWait time.Duration, want int) {
+	var numFree int
+	if !waitCondition(maxWait, 5*time.Millisecond, func() bool {
+		numFree = db.numFreeConns()
+		return numFree == want
+	}) {
+		t.Fatalf("free conns after hitting EOF = %d; want %d", numFree, want)
+	}
+}
+
+func waitForRowsClose(t *testing.T, rows *Rows, maxWait time.Duration) {
+	if !waitCondition(maxWait, 5*time.Millisecond, func() bool {
+		rows.closemu.RLock()
+		defer rows.closemu.RUnlock()
+		return rows.closed
+	}) {
+		t.Fatal("failed to close rows")
+	}
+}
+
+// TestQueryContextWait ensures that rows and all internal statements are closed when
+// a query context is closed during execution.
+func TestQueryContextWait(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	prepares0 := numPrepares(t, db)
+
+	// TODO(kardianos): convert this from using a timeout to using an explicit
+	// cancel when the query signals that it is "executing" the query.
+	ctx, cancel := context.WithTimeout(context.Background(), 300*time.Millisecond)
+	defer cancel()
+
+	// This will trigger the *fakeConn.Prepare method which will take time
+	// performing the query. The ctxDriverPrepare func will check the context
+	// after this and close the rows and return an error.
+	_, err := db.QueryContext(ctx, "WAIT|1s|SELECT|people|age,name|")
+	if err != context.DeadlineExceeded {
+		t.Fatalf("expected QueryContext to error with context deadline exceeded but returned %v", err)
+	}
+
+	// Verify closed rows connection after error condition.
+	waitForFree(t, db, 5*time.Second, 1)
+	if prepares := numPrepares(t, db) - prepares0; prepares != 1 {
+		// TODO(kardianos): if the context timeouts before the db.QueryContext
+		// executes this check may fail. After adjusting how the context
+		// is canceled above revert this back to a Fatal error.
+		t.Logf("executed %d Prepare statements; want 1", prepares)
+	}
+}
+
+// TestTxContextWait tests the transaction behavior when the tx context is canceled
+// during execution of the query.
+func TestTxContextWait(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Millisecond)
+	defer cancel()
+
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		// Guard against the context being canceled before BeginTx completes.
+		if err == context.DeadlineExceeded {
+			t.Skip("tx context canceled prior to first use")
+		}
+		t.Fatal(err)
+	}
+	tx.keepConnOnRollback = false
+
+	// This will trigger the *fakeConn.Prepare method which will take time
+	// performing the query. The ctxDriverPrepare func will check the context
+	// after this and close the rows and return an error.
+	_, err = tx.QueryContext(ctx, "WAIT|1s|SELECT|people|age,name|")
+	if err != context.DeadlineExceeded {
+		t.Fatalf("expected QueryContext to error with context deadline exceeded but returned %v", err)
+	}
+
+	waitForFree(t, db, 5*time.Second, 0)
+}
+
+// TestTxContextWaitNoDiscard is the same as TestTxContextWait, but should not discard
+// the final connection.
+func TestTxContextWaitNoDiscard(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Millisecond)
+	defer cancel()
+
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		// Guard against the context being canceled before BeginTx completes.
+		if err == context.DeadlineExceeded {
+			t.Skip("tx context canceled prior to first use")
+		}
+		t.Fatal(err)
+	}
+
+	// This will trigger the *fakeConn.Prepare method which will take time
+	// performing the query. The ctxDriverPrepare func will check the context
+	// after this and close the rows and return an error.
+	_, err = tx.QueryContext(ctx, "WAIT|1s|SELECT|people|age,name|")
+	if err != context.DeadlineExceeded {
+		t.Fatalf("expected QueryContext to error with context deadline exceeded but returned %v", err)
+	}
+
+	waitForFree(t, db, 5*time.Second, 1)
+}
+
+// TestUnsupportedOptions checks that the database fails when a driver that
+// doesn't implement ConnBeginTx is used with non-default options and an
+// un-cancellable context.
+func TestUnsupportedOptions(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	_, err := db.BeginTx(context.Background(), &TxOptions{
+		Isolation: LevelSerializable, ReadOnly: true,
+	})
+	if err == nil {
+		t.Fatal("expected error when using unsupported options, got nil")
+	}
+}
+
+func TestMultiResultSetQuery(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	prepares0 := numPrepares(t, db)
+	rows, err := db.Query("SELECT|people|age,name|;SELECT|people|name|")
+	if err != nil {
+		t.Fatalf("Query: %v", err)
+	}
+	type row1 struct {
+		age  int
+		name string
+	}
+	type row2 struct {
+		name string
+	}
+	got1 := []row1{}
+	for rows.Next() {
+		var r row1
+		err = rows.Scan(&r.age, &r.name)
+		if err != nil {
+			t.Fatalf("Scan: %v", err)
+		}
+		got1 = append(got1, r)
+	}
+	err = rows.Err()
+	if err != nil {
+		t.Fatalf("Err: %v", err)
+	}
+	want1 := []row1{
+		{age: 1, name: "Alice"},
+		{age: 2, name: "Bob"},
+		{age: 3, name: "Chris"},
+	}
+	if !reflect.DeepEqual(got1, want1) {
+		t.Errorf("mismatch.\n got1: %#v\nwant: %#v", got1, want1)
+	}
+
+	if !rows.NextResultSet() {
+		t.Errorf("expected another result set")
+	}
+
+	got2 := []row2{}
+	for rows.Next() {
+		var r row2
+		err = rows.Scan(&r.name)
+		if err != nil {
+			t.Fatalf("Scan: %v", err)
+		}
+		got2 = append(got2, r)
+	}
+	err = rows.Err()
+	if err != nil {
+		t.Fatalf("Err: %v", err)
+	}
+	want2 := []row2{
+		{name: "Alice"},
+		{name: "Bob"},
+		{name: "Chris"},
+	}
+	if !reflect.DeepEqual(got2, want2) {
+		t.Errorf("mismatch.\n got: %#v\nwant: %#v", got2, want2)
+	}
+	if rows.NextResultSet() {
+		t.Errorf("expected no more result sets")
+	}
+
+	// And verify that the final rows.Next() call, which hit EOF,
+	// also closed the rows connection.
+	waitForFree(t, db, 5*time.Second, 1)
+	if prepares := numPrepares(t, db) - prepares0; prepares != 1 {
+		t.Errorf("executed %d Prepare statements; want 1", prepares)
+	}
+}
+
+func TestQueryNamedArg(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	prepares0 := numPrepares(t, db)
+	rows, err := db.Query(
+		// Ensure the name and age parameters only match on placeholder name, not position.
+		"SELECT|people|age,name|name=?name,age=?age",
+		Named("age", 2),
+		Named("name", "Bob"),
+	)
+	if err != nil {
+		t.Fatalf("Query: %v", err)
+	}
+	type row struct {
+		age  int
+		name string
+	}
+	got := []row{}
+	for rows.Next() {
+		var r row
+		err = rows.Scan(&r.age, &r.name)
+		if err != nil {
+			t.Fatalf("Scan: %v", err)
+		}
+		got = append(got, r)
+	}
+	err = rows.Err()
+	if err != nil {
+		t.Fatalf("Err: %v", err)
+	}
+	want := []row{
+		{age: 2, name: "Bob"},
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("mismatch.\n got: %#v\nwant: %#v", got, want)
+	}
+
+	// And verify that the final rows.Next() call, which hit EOF,
+	// also closed the rows connection.
+	if n := db.numFreeConns(); n != 1 {
+		t.Fatalf("free conns after query hitting EOF = %d; want 1", n)
+	}
+	if prepares := numPrepares(t, db) - prepares0; prepares != 1 {
+		t.Errorf("executed %d Prepare statements; want 1", prepares)
+	}
+}
+
+func TestPoolExhaustOnCancel(t *testing.T) {
+	if testing.Short() {
+		t.Skip("long test")
+	}
+
+	max := 3
+	var saturate, saturateDone sync.WaitGroup
+	saturate.Add(max)
+	saturateDone.Add(max)
+
+	donePing := make(chan bool)
+	state := 0
+
+	// waiter will be called for all queries, including
+	// initial setup queries. The state is only assigned when
+	// no queries are made.
+	//
+	// Only allow the first batch of queries to finish once the
+	// second batch of Ping queries have finished.
+	waiter := func(ctx context.Context) {
+		switch state {
+		case 0:
+			// Nothing. Initial database setup.
+		case 1:
+			saturate.Done()
+			select {
+			case <-ctx.Done():
+			case <-donePing:
+			}
+		case 2:
+		}
+	}
+	db := newTestDBConnector(t, &fakeConnector{waiter: waiter}, "people")
+	defer closeDB(t, db)
+
+	db.SetMaxOpenConns(max)
+
+	// First saturate the connection pool.
+	// Then start new requests for a connection that is cancelled after it is requested.
+
+	state = 1
+	for i := 0; i < max; i++ {
+		go func() {
+			rows, err := db.Query("SELECT|people|name,photo|")
+			if err != nil {
+				t.Errorf("Query: %v", err)
+				return
+			}
+			rows.Close()
+			saturateDone.Done()
+		}()
+	}
+
+	saturate.Wait()
+	if t.Failed() {
+		t.FailNow()
+	}
+	state = 2
+
+	// Now cancel the request while it is waiting.
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+
+	for i := 0; i < max; i++ {
+		ctxReq, cancelReq := context.WithCancel(ctx)
+		go func() {
+			time.Sleep(100 * time.Millisecond)
+			cancelReq()
+		}()
+		err := db.PingContext(ctxReq)
+		if err != context.Canceled {
+			t.Fatalf("PingContext (Exhaust): %v", err)
+		}
+	}
+	close(donePing)
+	saturateDone.Wait()
+
+	// Now try to open a normal connection.
+	err := db.PingContext(ctx)
+	if err != nil {
+		t.Fatalf("PingContext (Normal): %v", err)
+	}
+}
+
+func TestRowsColumns(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	rows, err := db.Query("SELECT|people|age,name|")
+	if err != nil {
+		t.Fatalf("Query: %v", err)
+	}
+	cols, err := rows.Columns()
+	if err != nil {
+		t.Fatalf("Columns: %v", err)
+	}
+	want := []string{"age", "name"}
+	if !reflect.DeepEqual(cols, want) {
+		t.Errorf("got %#v; want %#v", cols, want)
+	}
+	if err := rows.Close(); err != nil {
+		t.Errorf("error closing rows: %s", err)
+	}
+}
+
+func TestRowsColumnTypes(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	rows, err := db.Query("SELECT|people|age,name|")
+	if err != nil {
+		t.Fatalf("Query: %v", err)
+	}
+	tt, err := rows.ColumnTypes()
+	if err != nil {
+		t.Fatalf("ColumnTypes: %v", err)
+	}
+
+	types := make([]reflect.Type, len(tt))
+	for i, tp := range tt {
+		st := tp.ScanType()
+		if st == nil {
+			t.Errorf("scantype is null for column %q", tp.Name())
+			continue
+		}
+		types[i] = st
+	}
+	values := make([]interface{}, len(tt))
+	for i := range values {
+		values[i] = reflect.New(types[i]).Interface()
+	}
+	ct := 0
+	for rows.Next() {
+		err = rows.Scan(values...)
+		if err != nil {
+			t.Fatalf("failed to scan values in %v", err)
+		}
+		if ct == 1 {
+			if age := *values[0].(*int32); age != 2 {
+				t.Errorf("Expected 2, got %v", age)
+			}
+			if name := *values[1].(*string); name != "Bob" {
+				t.Errorf("Expected Bob, got %v", name)
+			}
+		}
+		ct++
+	}
+	if ct != 3 {
+		t.Errorf("expected 3 rows, got %d", ct)
+	}
+
+	if err := rows.Close(); err != nil {
+		t.Errorf("error closing rows: %s", err)
+	}
+}
+
+func TestQueryRow(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	var name string
+	var age int
+	var birthday time.Time
+
+	err := db.QueryRow("SELECT|people|age,name|age=?", 3).Scan(&age)
+	if err == nil || !strings.Contains(err.Error(), "expected 2 destination arguments") {
+		t.Errorf("expected error from wrong number of arguments; actually got: %v", err)
+	}
+
+	err = db.QueryRow("SELECT|people|bdate|age=?", 3).Scan(&birthday)
+	if err != nil || !birthday.Equal(chrisBirthday) {
+		t.Errorf("chris birthday = %v, err = %v; want %v", birthday, err, chrisBirthday)
+	}
+
+	err = db.QueryRow("SELECT|people|age,name|age=?", 2).Scan(&age, &name)
+	if err != nil {
+		t.Fatalf("age QueryRow+Scan: %v", err)
+	}
+	if name != "Bob" {
+		t.Errorf("expected name Bob, got %q", name)
+	}
+	if age != 2 {
+		t.Errorf("expected age 2, got %d", age)
+	}
+
+	err = db.QueryRow("SELECT|people|age,name|name=?", "Alice").Scan(&age, &name)
+	if err != nil {
+		t.Fatalf("name QueryRow+Scan: %v", err)
+	}
+	if name != "Alice" {
+		t.Errorf("expected name Alice, got %q", name)
+	}
+	if age != 1 {
+		t.Errorf("expected age 1, got %d", age)
+	}
+
+	var photo []byte
+	err = db.QueryRow("SELECT|people|photo|name=?", "Alice").Scan(&photo)
+	if err != nil {
+		t.Fatalf("photo QueryRow+Scan: %v", err)
+	}
+	want := []byte("APHOTO")
+	if !reflect.DeepEqual(photo, want) {
+		t.Errorf("photo = %q; want %q", photo, want)
+	}
+}
+
+func TestRowErr(t *testing.T) {
+	db := newTestDB(t, "people")
+
+	err := db.QueryRowContext(context.Background(), "SELECT|people|bdate|age=?", 3).Err()
+	if err != nil {
+		t.Errorf("Unexpected err = %v; want %v", err, nil)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	err = db.QueryRowContext(ctx, "SELECT|people|bdate|age=?", 3).Err()
+	exp := "context canceled"
+	if err == nil || !strings.Contains(err.Error(), exp) {
+		t.Errorf("Expected err = %v; got %v", exp, err)
+	}
+}
+
+func TestTxRollbackCommitErr(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = tx.Rollback()
+	if err != nil {
+		t.Errorf("expected nil error from Rollback; got %v", err)
+	}
+	err = tx.Commit()
+	if err != ErrTxDone {
+		t.Errorf("expected %q from Commit; got %q", ErrTxDone, err)
+	}
+
+	tx, err = db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = tx.Commit()
+	if err != nil {
+		t.Errorf("expected nil error from Commit; got %v", err)
+	}
+	err = tx.Rollback()
+	if err != ErrTxDone {
+		t.Errorf("expected %q from Rollback; got %q", ErrTxDone, err)
+	}
+}
+
+func TestStatementErrorAfterClose(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	stmt, err := db.Prepare("SELECT|people|age|name=?")
+	if err != nil {
+		t.Fatalf("Prepare: %v", err)
+	}
+	err = stmt.Close()
+	if err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+	var name string
+	err = stmt.QueryRow("foo").Scan(&name)
+	if err == nil {
+		t.Errorf("expected error from QueryRow.Scan after Stmt.Close")
+	}
+}
+
+func TestStatementQueryRow(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	stmt, err := db.Prepare("SELECT|people|age|name=?")
+	if err != nil {
+		t.Fatalf("Prepare: %v", err)
+	}
+	defer stmt.Close()
+	var age int
+	for n, tt := range []struct {
+		name string
+		want int
+	}{
+		{"Alice", 1},
+		{"Bob", 2},
+		{"Chris", 3},
+	} {
+		if err := stmt.QueryRow(tt.name).Scan(&age); err != nil {
+			t.Errorf("%d: on %q, QueryRow/Scan: %v", n, tt.name, err)
+		} else if age != tt.want {
+			t.Errorf("%d: age=%d, want %d", n, age, tt.want)
+		}
+	}
+}
+
+type stubDriverStmt struct {
+	err error
+}
+
+func (s stubDriverStmt) Close() error {
+	return s.err
+}
+
+func (s stubDriverStmt) NumInput() int {
+	return -1
+}
+
+func (s stubDriverStmt) Exec(args []driver.Value) (driver.Result, error) {
+	return nil, nil
+}
+
+func (s stubDriverStmt) Query(args []driver.Value) (driver.Rows, error) {
+	return nil, nil
+}
+
+// golang.org/issue/12798
+func TestStatementClose(t *testing.T) {
+	want := errors.New("STMT ERROR")
+
+	tests := []struct {
+		stmt *Stmt
+		msg  string
+	}{
+		{&Stmt{stickyErr: want}, "stickyErr not propagated"},
+		{&Stmt{cg: &Tx{}, cgds: &driverStmt{Locker: &sync.Mutex{}, si: stubDriverStmt{want}}}, "driverStmt.Close() error not propagated"},
+	}
+	for _, test := range tests {
+		if err := test.stmt.Close(); err != want {
+			t.Errorf("%s. Got stmt.Close() = %v, want = %v", test.msg, err, want)
+		}
+	}
+}
+
+// golang.org/issue/3734
+func TestStatementQueryRowConcurrent(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	stmt, err := db.Prepare("SELECT|people|age|name=?")
+	if err != nil {
+		t.Fatalf("Prepare: %v", err)
+	}
+	defer stmt.Close()
+
+	const n = 10
+	ch := make(chan error, n)
+	for i := 0; i < n; i++ {
+		go func() {
+			var age int
+			err := stmt.QueryRow("Alice").Scan(&age)
+			if err == nil && age != 1 {
+				err = fmt.Errorf("unexpected age %d", age)
+			}
+			ch <- err
+		}()
+	}
+	for i := 0; i < n; i++ {
+		if err := <-ch; err != nil {
+			t.Error(err)
+		}
+	}
+}
+
+// just a test of fakedb itself
+func TestBogusPreboundParameters(t *testing.T) {
+	db := newTestDB(t, "foo")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32,dead=bool")
+	_, err := db.Prepare("INSERT|t1|name=?,age=bogusconversion")
+	if err == nil {
+		t.Fatalf("expected error")
+	}
+	if err.Error() != `fakedb: invalid conversion to int32 from "bogusconversion"` {
+		t.Errorf("unexpected error: %v", err)
+	}
+}
+
+func TestExec(t *testing.T) {
+	db := newTestDB(t, "foo")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32,dead=bool")
+	stmt, err := db.Prepare("INSERT|t1|name=?,age=?")
+	if err != nil {
+		t.Errorf("Stmt, err = %v, %v", stmt, err)
+	}
+	defer stmt.Close()
+
+	type execTest struct {
+		args    []interface{}
+		wantErr string
+	}
+	execTests := []execTest{
+		// Okay:
+		{[]interface{}{"Brad", 31}, ""},
+		{[]interface{}{"Brad", int64(31)}, ""},
+		{[]interface{}{"Bob", "32"}, ""},
+		{[]interface{}{7, 9}, ""},
+
+		// Invalid conversions:
+		{[]interface{}{"Brad", int64(0xFFFFFFFF)}, "sql: converting argument $2 type: sql/driver: value 4294967295 overflows int32"},
+		{[]interface{}{"Brad", "strconv fail"}, `sql: converting argument $2 type: sql/driver: value "strconv fail" can't be converted to int32`},
+
+		// Wrong number of args:
+		{[]interface{}{}, "sql: expected 2 arguments, got 0"},
+		{[]interface{}{1, 2, 3}, "sql: expected 2 arguments, got 3"},
+	}
+	for n, et := range execTests {
+		_, err := stmt.Exec(et.args...)
+		errStr := ""
+		if err != nil {
+			errStr = err.Error()
+		}
+		if errStr != et.wantErr {
+			t.Errorf("stmt.Execute #%d: for %v, got error %q, want error %q",
+				n, et.args, errStr, et.wantErr)
+		}
+	}
+}
+
+func TestTxPrepare(t *testing.T) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32,dead=bool")
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatalf("Begin = %v", err)
+	}
+	stmt, err := tx.Prepare("INSERT|t1|name=?,age=?")
+	if err != nil {
+		t.Fatalf("Stmt, err = %v, %v", stmt, err)
+	}
+	defer stmt.Close()
+	_, err = stmt.Exec("Bobby", 7)
+	if err != nil {
+		t.Fatalf("Exec = %v", err)
+	}
+	err = tx.Commit()
+	if err != nil {
+		t.Fatalf("Commit = %v", err)
+	}
+	// Commit() should have closed the statement
+	if !stmt.closed {
+		t.Fatal("Stmt not closed after Commit")
+	}
+}
+
+func TestTxStmt(t *testing.T) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32,dead=bool")
+	stmt, err := db.Prepare("INSERT|t1|name=?,age=?")
+	if err != nil {
+		t.Fatalf("Stmt, err = %v, %v", stmt, err)
+	}
+	defer stmt.Close()
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatalf("Begin = %v", err)
+	}
+	txs := tx.Stmt(stmt)
+	defer txs.Close()
+	_, err = txs.Exec("Bobby", 7)
+	if err != nil {
+		t.Fatalf("Exec = %v", err)
+	}
+	err = tx.Commit()
+	if err != nil {
+		t.Fatalf("Commit = %v", err)
+	}
+	// Commit() should have closed the statement
+	if !txs.closed {
+		t.Fatal("Stmt not closed after Commit")
+	}
+}
+
+func TestTxStmtPreparedOnce(t *testing.T) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32")
+
+	prepares0 := numPrepares(t, db)
+
+	// db.Prepare increments numPrepares.
+	stmt, err := db.Prepare("INSERT|t1|name=?,age=?")
+	if err != nil {
+		t.Fatalf("Stmt, err = %v, %v", stmt, err)
+	}
+	defer stmt.Close()
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatalf("Begin = %v", err)
+	}
+
+	txs1 := tx.Stmt(stmt)
+	txs2 := tx.Stmt(stmt)
+
+	_, err = txs1.Exec("Go", 7)
+	if err != nil {
+		t.Fatalf("Exec = %v", err)
+	}
+	txs1.Close()
+
+	_, err = txs2.Exec("Gopher", 8)
+	if err != nil {
+		t.Fatalf("Exec = %v", err)
+	}
+	txs2.Close()
+
+	err = tx.Commit()
+	if err != nil {
+		t.Fatalf("Commit = %v", err)
+	}
+
+	if prepares := numPrepares(t, db) - prepares0; prepares != 1 {
+		t.Errorf("executed %d Prepare statements; want 1", prepares)
+	}
+}
+
+func TestTxStmtClosedRePrepares(t *testing.T) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32")
+
+	prepares0 := numPrepares(t, db)
+
+	// db.Prepare increments numPrepares.
+	stmt, err := db.Prepare("INSERT|t1|name=?,age=?")
+	if err != nil {
+		t.Fatalf("Stmt, err = %v, %v", stmt, err)
+	}
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatalf("Begin = %v", err)
+	}
+	err = stmt.Close()
+	if err != nil {
+		t.Fatalf("stmt.Close() = %v", err)
+	}
+	// tx.Stmt increments numPrepares because stmt is closed.
+	txs := tx.Stmt(stmt)
+	if txs.stickyErr != nil {
+		t.Fatal(txs.stickyErr)
+	}
+	if txs.parentStmt != nil {
+		t.Fatal("expected nil parentStmt")
+	}
+	_, err = txs.Exec(`Eric`, 82)
+	if err != nil {
+		t.Fatalf("txs.Exec = %v", err)
+	}
+
+	err = txs.Close()
+	if err != nil {
+		t.Fatalf("txs.Close = %v", err)
+	}
+
+	tx.Rollback()
+
+	if prepares := numPrepares(t, db) - prepares0; prepares != 2 {
+		t.Errorf("executed %d Prepare statements; want 2", prepares)
+	}
+}
+
+func TestParentStmtOutlivesTxStmt(t *testing.T) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32")
+
+	// Make sure everything happens on the same connection.
+	db.SetMaxOpenConns(1)
+
+	prepares0 := numPrepares(t, db)
+
+	// db.Prepare increments numPrepares.
+	stmt, err := db.Prepare("INSERT|t1|name=?,age=?")
+	if err != nil {
+		t.Fatalf("Stmt, err = %v, %v", stmt, err)
+	}
+	defer stmt.Close()
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatalf("Begin = %v", err)
+	}
+	txs := tx.Stmt(stmt)
+	if len(stmt.css) != 1 {
+		t.Fatalf("len(stmt.css) = %v; want 1", len(stmt.css))
+	}
+	err = txs.Close()
+	if err != nil {
+		t.Fatalf("txs.Close() = %v", err)
+	}
+	err = tx.Rollback()
+	if err != nil {
+		t.Fatalf("tx.Rollback() = %v", err)
+	}
+	// txs must not be valid.
+	_, err = txs.Exec("Suzan", 30)
+	if err == nil {
+		t.Fatalf("txs.Exec(), expected err")
+	}
+	// Stmt must still be valid.
+	_, err = stmt.Exec("Janina", 25)
+	if err != nil {
+		t.Fatalf("stmt.Exec() = %v", err)
+	}
+
+	if prepares := numPrepares(t, db) - prepares0; prepares != 1 {
+		t.Errorf("executed %d Prepare statements; want 1", prepares)
+	}
+}
+
+// Test that tx.Stmt called with a statement already
+// associated with tx as argument re-prepares the same
+// statement again.
+func TestTxStmtFromTxStmtRePrepares(t *testing.T) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32")
+	prepares0 := numPrepares(t, db)
+	// db.Prepare increments numPrepares.
+	stmt, err := db.Prepare("INSERT|t1|name=?,age=?")
+	if err != nil {
+		t.Fatalf("Stmt, err = %v, %v", stmt, err)
+	}
+	defer stmt.Close()
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatalf("Begin = %v", err)
+	}
+	txs1 := tx.Stmt(stmt)
+
+	// tx.Stmt(txs1) increments numPrepares because txs1 already
+	// belongs to a transaction (albeit the same transaction).
+	txs2 := tx.Stmt(txs1)
+	if txs2.stickyErr != nil {
+		t.Fatal(txs2.stickyErr)
+	}
+	if txs2.parentStmt != nil {
+		t.Fatal("expected nil parentStmt")
+	}
+	_, err = txs2.Exec(`Eric`, 82)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = txs1.Close()
+	if err != nil {
+		t.Fatalf("txs1.Close = %v", err)
+	}
+	err = txs2.Close()
+	if err != nil {
+		t.Fatalf("txs1.Close = %v", err)
+	}
+	err = tx.Rollback()
+	if err != nil {
+		t.Fatalf("tx.Rollback = %v", err)
+	}
+
+	if prepares := numPrepares(t, db) - prepares0; prepares != 2 {
+		t.Errorf("executed %d Prepare statements; want 2", prepares)
+	}
+}
+
+// Issue: https://golang.org/issue/2784
+// This test didn't fail before because we got lucky with the fakedb driver.
+// It was failing, and now not, in github.com/bradfitz/go-sql-test
+func TestTxQuery(t *testing.T) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32,dead=bool")
+	exec(t, db, "INSERT|t1|name=Alice")
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tx.Rollback()
+
+	r, err := tx.Query("SELECT|t1|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer r.Close()
+
+	if !r.Next() {
+		if r.Err() != nil {
+			t.Fatal(r.Err())
+		}
+		t.Fatal("expected one row")
+	}
+
+	var x string
+	err = r.Scan(&x)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestTxQueryInvalid(t *testing.T) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tx.Rollback()
+
+	_, err = tx.Query("SELECT|t1|name|")
+	if err == nil {
+		t.Fatal("Error expected")
+	}
+}
+
+// Tests fix for issue 4433, that retries in Begin happen when
+// conn.Begin() returns ErrBadConn
+func TestTxErrBadConn(t *testing.T) {
+	db, err := Open("test", fakeDBName+";badConn")
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	if _, err := db.Exec("WIPE"); err != nil {
+		t.Fatalf("exec wipe: %v", err)
+	}
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32,dead=bool")
+	stmt, err := db.Prepare("INSERT|t1|name=?,age=?")
+	if err != nil {
+		t.Fatalf("Stmt, err = %v, %v", stmt, err)
+	}
+	defer stmt.Close()
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatalf("Begin = %v", err)
+	}
+	txs := tx.Stmt(stmt)
+	defer txs.Close()
+	_, err = txs.Exec("Bobby", 7)
+	if err != nil {
+		t.Fatalf("Exec = %v", err)
+	}
+	err = tx.Commit()
+	if err != nil {
+		t.Fatalf("Commit = %v", err)
+	}
+}
+
+func TestConnQuery(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	conn.dc.ci.(*fakeConn).skipDirtySession = true
+	defer conn.Close()
+
+	var name string
+	err = conn.QueryRowContext(ctx, "SELECT|people|name|age=?", 3).Scan(&name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if name != "Chris" {
+		t.Fatalf("unexpected result, got %q want Chris", name)
+	}
+
+	err = conn.PingContext(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestConnRaw(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	conn.dc.ci.(*fakeConn).skipDirtySession = true
+	defer conn.Close()
+
+	sawFunc := false
+	err = conn.Raw(func(dc interface{}) error {
+		sawFunc = true
+		if _, ok := dc.(*fakeConn); !ok {
+			return fmt.Errorf("got %T want *fakeConn", dc)
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !sawFunc {
+		t.Fatal("Raw func not called")
+	}
+
+	func() {
+		defer func() {
+			x := recover()
+			if x == nil {
+				t.Fatal("expected panic")
+			}
+			conn.closemu.Lock()
+			closed := conn.dc == nil
+			conn.closemu.Unlock()
+			if !closed {
+				t.Fatal("expected connection to be closed after panic")
+			}
+		}()
+		err = conn.Raw(func(dc interface{}) error {
+			panic("Conn.Raw panic should return an error")
+		})
+		t.Fatal("expected panic from Raw func")
+	}()
+}
+
+func TestCursorFake(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*30)
+	defer cancel()
+
+	exec(t, db, "CREATE|peoplecursor|list=table")
+	exec(t, db, "INSERT|peoplecursor|list=people!name!age")
+
+	rows, err := db.QueryContext(ctx, `SELECT|peoplecursor|list|`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer rows.Close()
+
+	if !rows.Next() {
+		t.Fatal("no rows")
+	}
+	var cursor = &Rows{}
+	err = rows.Scan(cursor)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer cursor.Close()
+
+	const expectedRows = 3
+	var currentRow int64
+
+	var n int64
+	var s string
+	for cursor.Next() {
+		currentRow++
+		err = cursor.Scan(&s, &n)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if n != currentRow {
+			t.Errorf("expected number(Age)=%d, got %d", currentRow, n)
+		}
+	}
+	if currentRow != expectedRows {
+		t.Errorf("expected %d rows, got %d rows", expectedRows, currentRow)
+	}
+}
+
+func TestInvalidNilValues(t *testing.T) {
+	var date1 time.Time
+	var date2 int
+
+	tests := []struct {
+		name          string
+		input         interface{}
+		expectedError string
+	}{
+		{
+			name:          "time.Time",
+			input:         &date1,
+			expectedError: `sql: Scan error on column index 0, name "bdate": unsupported Scan, storing driver.Value type <nil> into type *time.Time`,
+		},
+		{
+			name:          "int",
+			input:         &date2,
+			expectedError: `sql: Scan error on column index 0, name "bdate": converting NULL to int is unsupported`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			db := newTestDB(t, "people")
+			defer closeDB(t, db)
+
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+			conn, err := db.Conn(ctx)
+			if err != nil {
+				t.Fatal(err)
+			}
+			conn.dc.ci.(*fakeConn).skipDirtySession = true
+			defer conn.Close()
+
+			err = conn.QueryRowContext(ctx, "SELECT|people|bdate|age=?", 1).Scan(tt.input)
+			if err == nil {
+				t.Fatal("expected error when querying nil column, but succeeded")
+			}
+			if err.Error() != tt.expectedError {
+				t.Fatalf("Expected error: %s\nReceived: %s", tt.expectedError, err.Error())
+			}
+
+			err = conn.PingContext(ctx)
+			if err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+}
+
+func TestConnTx(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	conn.dc.ci.(*fakeConn).skipDirtySession = true
+	defer conn.Close()
+
+	tx, err := conn.BeginTx(ctx, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	insertName, insertAge := "Nancy", 33
+	_, err = tx.ExecContext(ctx, "INSERT|people|name=?,age=?,photo=APHOTO", insertName, insertAge)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = tx.Commit()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var selectName string
+	err = conn.QueryRowContext(ctx, "SELECT|people|name|age=?", insertAge).Scan(&selectName)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if selectName != insertName {
+		t.Fatalf("got %q want %q", selectName, insertName)
+	}
+}
+
+// TestConnIsValid verifies that a database connection that should be discarded,
+// is actually discarded and does not re-enter the connection pool.
+// If the IsValid method from *fakeConn is removed, this test will fail.
+func TestConnIsValid(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	db.SetMaxOpenConns(1)
+
+	ctx := context.Background()
+
+	c, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = c.Raw(func(raw interface{}) error {
+		dc := raw.(*fakeConn)
+		dc.stickyBad = true
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	c.Close()
+
+	if len(db.freeConn) > 0 && db.freeConn[0].ci.(*fakeConn).stickyBad {
+		t.Fatal("bad connection returned to pool; expected bad connection to be discarded")
+	}
+}
+
+// Tests fix for issue 2542, that we release a lock when querying on
+// a closed connection.
+func TestIssue2542Deadlock(t *testing.T) {
+	db := newTestDB(t, "people")
+	closeDB(t, db)
+	for i := 0; i < 2; i++ {
+		_, err := db.Query("SELECT|people|age,name|")
+		if err == nil {
+			t.Fatalf("expected error")
+		}
+	}
+}
+
+// From golang.org/issue/3865
+func TestCloseStmtBeforeRows(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	s, err := db.Prepare("SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	r, err := s.Query()
+	if err != nil {
+		s.Close()
+		t.Fatal(err)
+	}
+
+	err = s.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	r.Close()
+}
+
+// Tests fix for issue 2788, that we bind nil to a []byte if the
+// value in the column is sql null
+func TestNullByteSlice(t *testing.T) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t|id=int32,name=nullstring")
+	exec(t, db, "INSERT|t|id=10,name=?", nil)
+
+	var name []byte
+
+	err := db.QueryRow("SELECT|t|name|id=?", 10).Scan(&name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if name != nil {
+		t.Fatalf("name []byte should be nil for null column value, got: %#v", name)
+	}
+
+	exec(t, db, "INSERT|t|id=11,name=?", "bob")
+	err = db.QueryRow("SELECT|t|name|id=?", 11).Scan(&name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(name) != "bob" {
+		t.Fatalf("name []byte should be bob, got: %q", string(name))
+	}
+}
+
+func TestPointerParamsAndScans(t *testing.T) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t|id=int32,name=nullstring")
+
+	bob := "bob"
+	var name *string
+
+	name = &bob
+	exec(t, db, "INSERT|t|id=10,name=?", name)
+	name = nil
+	exec(t, db, "INSERT|t|id=20,name=?", name)
+
+	err := db.QueryRow("SELECT|t|name|id=?", 10).Scan(&name)
+	if err != nil {
+		t.Fatalf("querying id 10: %v", err)
+	}
+	if name == nil {
+		t.Errorf("id 10's name = nil; want bob")
+	} else if *name != "bob" {
+		t.Errorf("id 10's name = %q; want bob", *name)
+	}
+
+	err = db.QueryRow("SELECT|t|name|id=?", 20).Scan(&name)
+	if err != nil {
+		t.Fatalf("querying id 20: %v", err)
+	}
+	if name != nil {
+		t.Errorf("id 20 = %q; want nil", *name)
+	}
+}
+
+func TestQueryRowClosingStmt(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	var name string
+	var age int
+	err := db.QueryRow("SELECT|people|age,name|age=?", 3).Scan(&age, &name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(db.freeConn) != 1 {
+		t.Fatalf("expected 1 free conn")
+	}
+	fakeConn := db.freeConn[0].ci.(*fakeConn)
+	if made, closed := fakeConn.stmtsMade, fakeConn.stmtsClosed; made != closed {
+		t.Errorf("statement close mismatch: made %d, closed %d", made, closed)
+	}
+}
+
+var atomicRowsCloseHook atomic.Value // of func(*Rows, *error)
+
+func init() {
+	rowsCloseHook = func() func(*Rows, *error) {
+		fn, _ := atomicRowsCloseHook.Load().(func(*Rows, *error))
+		return fn
+	}
+}
+
+func setRowsCloseHook(fn func(*Rows, *error)) {
+	if fn == nil {
+		// Can't change an atomic.Value back to nil, so set it to this
+		// no-op func instead.
+		fn = func(*Rows, *error) {}
+	}
+	atomicRowsCloseHook.Store(fn)
+}
+
+// Test issue 6651
+func TestIssue6651(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	var v string
+
+	want := "error in rows.Next"
+	rowsCursorNextHook = func(dest []driver.Value) error {
+		return fmt.Errorf(want)
+	}
+	defer func() { rowsCursorNextHook = nil }()
+
+	err := db.QueryRow("SELECT|people|name|").Scan(&v)
+	if err == nil || err.Error() != want {
+		t.Errorf("error = %q; want %q", err, want)
+	}
+	rowsCursorNextHook = nil
+
+	want = "error in rows.Close"
+	setRowsCloseHook(func(rows *Rows, err *error) {
+		*err = fmt.Errorf(want)
+	})
+	defer setRowsCloseHook(nil)
+	err = db.QueryRow("SELECT|people|name|").Scan(&v)
+	if err == nil || err.Error() != want {
+		t.Errorf("error = %q; want %q", err, want)
+	}
+}
+
+type nullTestRow struct {
+	nullParam    interface{}
+	notNullParam interface{}
+	scanNullVal  interface{}
+}
+
+type nullTestSpec struct {
+	nullType    string
+	notNullType string
+	rows        [6]nullTestRow
+}
+
+func TestNullStringParam(t *testing.T) {
+	spec := nullTestSpec{"nullstring", "string", [6]nullTestRow{
+		{NullString{"aqua", true}, "", NullString{"aqua", true}},
+		{NullString{"brown", false}, "", NullString{"", false}},
+		{"chartreuse", "", NullString{"chartreuse", true}},
+		{NullString{"darkred", true}, "", NullString{"darkred", true}},
+		{NullString{"eel", false}, "", NullString{"", false}},
+		{"foo", NullString{"black", false}, nil},
+	}}
+	nullTestRun(t, spec)
+}
+
+func TestNullInt64Param(t *testing.T) {
+	spec := nullTestSpec{"nullint64", "int64", [6]nullTestRow{
+		{NullInt64{31, true}, 1, NullInt64{31, true}},
+		{NullInt64{-22, false}, 1, NullInt64{0, false}},
+		{22, 1, NullInt64{22, true}},
+		{NullInt64{33, true}, 1, NullInt64{33, true}},
+		{NullInt64{222, false}, 1, NullInt64{0, false}},
+		{0, NullInt64{31, false}, nil},
+	}}
+	nullTestRun(t, spec)
+}
+
+func TestNullInt32Param(t *testing.T) {
+	spec := nullTestSpec{"nullint32", "int32", [6]nullTestRow{
+		{NullInt32{31, true}, 1, NullInt32{31, true}},
+		{NullInt32{-22, false}, 1, NullInt32{0, false}},
+		{22, 1, NullInt32{22, true}},
+		{NullInt32{33, true}, 1, NullInt32{33, true}},
+		{NullInt32{222, false}, 1, NullInt32{0, false}},
+		{0, NullInt32{31, false}, nil},
+	}}
+	nullTestRun(t, spec)
+}
+
+func TestNullFloat64Param(t *testing.T) {
+	spec := nullTestSpec{"nullfloat64", "float64", [6]nullTestRow{
+		{NullFloat64{31.2, true}, 1, NullFloat64{31.2, true}},
+		{NullFloat64{13.1, false}, 1, NullFloat64{0, false}},
+		{-22.9, 1, NullFloat64{-22.9, true}},
+		{NullFloat64{33.81, true}, 1, NullFloat64{33.81, true}},
+		{NullFloat64{222, false}, 1, NullFloat64{0, false}},
+		{10, NullFloat64{31.2, false}, nil},
+	}}
+	nullTestRun(t, spec)
+}
+
+func TestNullBoolParam(t *testing.T) {
+	spec := nullTestSpec{"nullbool", "bool", [6]nullTestRow{
+		{NullBool{false, true}, true, NullBool{false, true}},
+		{NullBool{true, false}, false, NullBool{false, false}},
+		{true, true, NullBool{true, true}},
+		{NullBool{true, true}, false, NullBool{true, true}},
+		{NullBool{true, false}, true, NullBool{false, false}},
+		{true, NullBool{true, false}, nil},
+	}}
+	nullTestRun(t, spec)
+}
+
+func TestNullTimeParam(t *testing.T) {
+	t0 := time.Time{}
+	t1 := time.Date(2000, 1, 1, 8, 9, 10, 11, time.UTC)
+	t2 := time.Date(2010, 1, 1, 8, 9, 10, 11, time.UTC)
+	spec := nullTestSpec{"nulldatetime", "datetime", [6]nullTestRow{
+		{NullTime{t1, true}, t2, NullTime{t1, true}},
+		{NullTime{t1, false}, t2, NullTime{t0, false}},
+		{t1, t2, NullTime{t1, true}},
+		{NullTime{t1, true}, t2, NullTime{t1, true}},
+		{NullTime{t1, false}, t2, NullTime{t0, false}},
+		{t2, NullTime{t1, false}, nil},
+	}}
+	nullTestRun(t, spec)
+}
+
+func nullTestRun(t *testing.T, spec nullTestSpec) {
+	db := newTestDB(t, "")
+	defer closeDB(t, db)
+	exec(t, db, fmt.Sprintf("CREATE|t|id=int32,name=string,nullf=%s,notnullf=%s", spec.nullType, spec.notNullType))
+
+	// Inserts with db.Exec:
+	exec(t, db, "INSERT|t|id=?,name=?,nullf=?,notnullf=?", 1, "alice", spec.rows[0].nullParam, spec.rows[0].notNullParam)
+	exec(t, db, "INSERT|t|id=?,name=?,nullf=?,notnullf=?", 2, "bob", spec.rows[1].nullParam, spec.rows[1].notNullParam)
+
+	// Inserts with a prepared statement:
+	stmt, err := db.Prepare("INSERT|t|id=?,name=?,nullf=?,notnullf=?")
+	if err != nil {
+		t.Fatalf("prepare: %v", err)
+	}
+	defer stmt.Close()
+	if _, err := stmt.Exec(3, "chris", spec.rows[2].nullParam, spec.rows[2].notNullParam); err != nil {
+		t.Errorf("exec insert chris: %v", err)
+	}
+	if _, err := stmt.Exec(4, "dave", spec.rows[3].nullParam, spec.rows[3].notNullParam); err != nil {
+		t.Errorf("exec insert dave: %v", err)
+	}
+	if _, err := stmt.Exec(5, "eleanor", spec.rows[4].nullParam, spec.rows[4].notNullParam); err != nil {
+		t.Errorf("exec insert eleanor: %v", err)
+	}
+
+	// Can't put null val into non-null col
+	if _, err := stmt.Exec(6, "bob", spec.rows[5].nullParam, spec.rows[5].notNullParam); err == nil {
+		t.Errorf("expected error inserting nil val with prepared statement Exec")
+	}
+
+	_, err = db.Exec("INSERT|t|id=?,name=?,nullf=?", 999, nil, nil)
+	if err == nil {
+		// TODO: this test fails, but it's just because
+		// fakeConn implements the optional Execer interface,
+		// so arguably this is the correct behavior. But
+		// maybe I should flesh out the fakeConn.Exec
+		// implementation so this properly fails.
+		// t.Errorf("expected error inserting nil name with Exec")
+	}
+
+	paramtype := reflect.TypeOf(spec.rows[0].nullParam)
+	bindVal := reflect.New(paramtype).Interface()
+
+	for i := 0; i < 5; i++ {
+		id := i + 1
+		if err := db.QueryRow("SELECT|t|nullf|id=?", id).Scan(bindVal); err != nil {
+			t.Errorf("id=%d Scan: %v", id, err)
+		}
+		bindValDeref := reflect.ValueOf(bindVal).Elem().Interface()
+		if !reflect.DeepEqual(bindValDeref, spec.rows[i].scanNullVal) {
+			t.Errorf("id=%d got %#v, want %#v", id, bindValDeref, spec.rows[i].scanNullVal)
+		}
+	}
+}
+
+// golang.org/issue/4859
+func TestQueryRowNilScanDest(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	var name *string // nil pointer
+	err := db.QueryRow("SELECT|people|name|").Scan(name)
+	want := `sql: Scan error on column index 0, name "name": destination pointer is nil`
+	if err == nil || err.Error() != want {
+		t.Errorf("error = %q; want %q", err.Error(), want)
+	}
+}
+
+func TestIssue4902(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	driver := db.Driver().(*fakeDriver)
+	opens0 := driver.openCount
+
+	var stmt *Stmt
+	var err error
+	for i := 0; i < 10; i++ {
+		stmt, err = db.Prepare("SELECT|people|name|")
+		if err != nil {
+			t.Fatal(err)
+		}
+		err = stmt.Close()
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	opens := driver.openCount - opens0
+	if opens > 1 {
+		t.Errorf("opens = %d; want <= 1", opens)
+		t.Logf("db = %#v", db)
+		t.Logf("driver = %#v", driver)
+		t.Logf("stmt = %#v", stmt)
+	}
+}
+
+// Issue 3857
+// This used to deadlock.
+func TestSimultaneousQueries(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tx.Rollback()
+
+	r1, err := tx.Query("SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer r1.Close()
+
+	r2, err := tx.Query("SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer r2.Close()
+}
+
+func TestMaxIdleConns(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	tx.Commit()
+	if got := len(db.freeConn); got != 1 {
+		t.Errorf("freeConns = %d; want 1", got)
+	}
+
+	db.SetMaxIdleConns(0)
+
+	if got := len(db.freeConn); got != 0 {
+		t.Errorf("freeConns after set to zero = %d; want 0", got)
+	}
+
+	tx, err = db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	tx.Commit()
+	if got := len(db.freeConn); got != 0 {
+		t.Errorf("freeConns = %d; want 0", got)
+	}
+}
+
+func TestMaxOpenConns(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
+	defer setHookpostCloseConn(nil)
+	setHookpostCloseConn(func(_ *fakeConn, err error) {
+		if err != nil {
+			t.Errorf("Error closing fakeConn: %v", err)
+		}
+	})
+
+	db := newTestDB(t, "magicquery")
+	defer closeDB(t, db)
+
+	driver := db.Driver().(*fakeDriver)
+
+	// Force the number of open connections to 0 so we can get an accurate
+	// count for the test
+	db.clearAllConns(t)
+
+	driver.mu.Lock()
+	opens0 := driver.openCount
+	closes0 := driver.closeCount
+	driver.mu.Unlock()
+
+	db.SetMaxIdleConns(10)
+	db.SetMaxOpenConns(10)
+
+	stmt, err := db.Prepare("SELECT|magicquery|op|op=?,millis=?")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Start 50 parallel slow queries.
+	const (
+		nquery      = 50
+		sleepMillis = 25
+		nbatch      = 2
+	)
+	var wg sync.WaitGroup
+	for batch := 0; batch < nbatch; batch++ {
+		for i := 0; i < nquery; i++ {
+			wg.Add(1)
+			go func() {
+				defer wg.Done()
+				var op string
+				if err := stmt.QueryRow("sleep", sleepMillis).Scan(&op); err != nil && err != ErrNoRows {
+					t.Error(err)
+				}
+			}()
+		}
+		// Sleep for twice the expected length of time for the
+		// batch of 50 queries above to finish before starting
+		// the next round.
+		time.Sleep(2 * sleepMillis * time.Millisecond)
+	}
+	wg.Wait()
+
+	if g, w := db.numFreeConns(), 10; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	if n := db.numDepsPollUntil(20, time.Second); n > 20 {
+		t.Errorf("number of dependencies = %d; expected <= 20", n)
+		db.dumpDeps(t)
+	}
+
+	driver.mu.Lock()
+	opens := driver.openCount - opens0
+	closes := driver.closeCount - closes0
+	driver.mu.Unlock()
+
+	if opens > 10 {
+		t.Logf("open calls = %d", opens)
+		t.Logf("close calls = %d", closes)
+		t.Errorf("db connections opened = %d; want <= 10", opens)
+		db.dumpDeps(t)
+	}
+
+	if err := stmt.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	if g, w := db.numFreeConns(), 10; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	if n := db.numDepsPollUntil(10, time.Second); n > 10 {
+		t.Errorf("number of dependencies = %d; expected <= 10", n)
+		db.dumpDeps(t)
+	}
+
+	db.SetMaxOpenConns(5)
+
+	if g, w := db.numFreeConns(), 5; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	if n := db.numDepsPollUntil(5, time.Second); n > 5 {
+		t.Errorf("number of dependencies = %d; expected 0", n)
+		db.dumpDeps(t)
+	}
+
+	db.SetMaxOpenConns(0)
+
+	if g, w := db.numFreeConns(), 5; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	if n := db.numDepsPollUntil(5, time.Second); n > 5 {
+		t.Errorf("number of dependencies = %d; expected 0", n)
+		db.dumpDeps(t)
+	}
+
+	db.clearAllConns(t)
+}
+
+// Issue 9453: tests that SetMaxOpenConns can be lowered at runtime
+// and affects the subsequent release of connections.
+func TestMaxOpenConnsOnBusy(t *testing.T) {
+	defer setHookpostCloseConn(nil)
+	setHookpostCloseConn(func(_ *fakeConn, err error) {
+		if err != nil {
+			t.Errorf("Error closing fakeConn: %v", err)
+		}
+	})
+
+	db := newTestDB(t, "magicquery")
+	defer closeDB(t, db)
+
+	db.SetMaxOpenConns(3)
+
+	ctx := context.Background()
+
+	conn0, err := db.conn(ctx, cachedOrNewConn)
+	if err != nil {
+		t.Fatalf("db open conn fail: %v", err)
+	}
+
+	conn1, err := db.conn(ctx, cachedOrNewConn)
+	if err != nil {
+		t.Fatalf("db open conn fail: %v", err)
+	}
+
+	conn2, err := db.conn(ctx, cachedOrNewConn)
+	if err != nil {
+		t.Fatalf("db open conn fail: %v", err)
+	}
+
+	if g, w := db.numOpen, 3; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	db.SetMaxOpenConns(2)
+	if g, w := db.numOpen, 3; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	conn0.releaseConn(nil)
+	conn1.releaseConn(nil)
+	if g, w := db.numOpen, 2; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	conn2.releaseConn(nil)
+	if g, w := db.numOpen, 2; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+}
+
+// Issue 10886: tests that all connection attempts return when more than
+// DB.maxOpen connections are in flight and the first DB.maxOpen fail.
+func TestPendingConnsAfterErr(t *testing.T) {
+	const (
+		maxOpen = 2
+		tryOpen = maxOpen*2 + 2
+	)
+
+	// No queries will be run.
+	db, err := Open("test", fakeDBName)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	defer closeDB(t, db)
+	defer func() {
+		for k, v := range db.lastPut {
+			t.Logf("%p: %v", k, v)
+		}
+	}()
+
+	db.SetMaxOpenConns(maxOpen)
+	db.SetMaxIdleConns(0)
+
+	errOffline := errors.New("db offline")
+
+	defer func() { setHookOpenErr(nil) }()
+
+	errs := make(chan error, tryOpen)
+
+	var opening sync.WaitGroup
+	opening.Add(tryOpen)
+
+	setHookOpenErr(func() error {
+		// Wait for all connections to enqueue.
+		opening.Wait()
+		return errOffline
+	})
+
+	for i := 0; i < tryOpen; i++ {
+		go func() {
+			opening.Done() // signal one connection is in flight
+			_, err := db.Exec("will never run")
+			errs <- err
+		}()
+	}
+
+	opening.Wait() // wait for all workers to begin running
+
+	const timeout = 5 * time.Second
+	to := time.NewTimer(timeout)
+	defer to.Stop()
+
+	// check that all connections fail without deadlock
+	for i := 0; i < tryOpen; i++ {
+		select {
+		case err := <-errs:
+			if got, want := err, errOffline; got != want {
+				t.Errorf("unexpected err: got %v, want %v", got, want)
+			}
+		case <-to.C:
+			t.Fatalf("orphaned connection request(s), still waiting after %v", timeout)
+		}
+	}
+
+	// Wait a reasonable time for the database to close all connections.
+	tick := time.NewTicker(3 * time.Millisecond)
+	defer tick.Stop()
+	for {
+		select {
+		case <-tick.C:
+			db.mu.Lock()
+			if db.numOpen == 0 {
+				db.mu.Unlock()
+				return
+			}
+			db.mu.Unlock()
+		case <-to.C:
+			// Closing the database will check for numOpen and fail the test.
+			return
+		}
+	}
+}
+
+func TestSingleOpenConn(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	db.SetMaxOpenConns(1)
+
+	rows, err := db.Query("SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = rows.Close(); err != nil {
+		t.Fatal(err)
+	}
+	// shouldn't deadlock
+	rows, err = db.Query("SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = rows.Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestStats(t *testing.T) {
+	db := newTestDB(t, "people")
+	stats := db.Stats()
+	if got := stats.OpenConnections; got != 1 {
+		t.Errorf("stats.OpenConnections = %d; want 1", got)
+	}
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	tx.Commit()
+
+	closeDB(t, db)
+	stats = db.Stats()
+	if got := stats.OpenConnections; got != 0 {
+		t.Errorf("stats.OpenConnections = %d; want 0", got)
+	}
+}
+
+func TestConnMaxLifetime(t *testing.T) {
+	t0 := time.Unix(1000000, 0)
+	offset := time.Duration(0)
+
+	nowFunc = func() time.Time { return t0.Add(offset) }
+	defer func() { nowFunc = time.Now }()
+
+	db := newTestDB(t, "magicquery")
+	defer closeDB(t, db)
+
+	driver := db.Driver().(*fakeDriver)
+
+	// Force the number of open connections to 0 so we can get an accurate
+	// count for the test
+	db.clearAllConns(t)
+
+	driver.mu.Lock()
+	opens0 := driver.openCount
+	closes0 := driver.closeCount
+	driver.mu.Unlock()
+
+	db.SetMaxIdleConns(10)
+	db.SetMaxOpenConns(10)
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	offset = time.Second
+	tx2, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tx.Commit()
+	tx2.Commit()
+
+	driver.mu.Lock()
+	opens := driver.openCount - opens0
+	closes := driver.closeCount - closes0
+	driver.mu.Unlock()
+
+	if opens != 2 {
+		t.Errorf("opens = %d; want 2", opens)
+	}
+	if closes != 0 {
+		t.Errorf("closes = %d; want 0", closes)
+	}
+	if g, w := db.numFreeConns(), 2; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	// Expire first conn
+	offset = 11 * time.Second
+	db.SetConnMaxLifetime(10 * time.Second)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tx, err = db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	tx2, err = db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	tx.Commit()
+	tx2.Commit()
+
+	driver.mu.Lock()
+	opens = driver.openCount - opens0
+	closes = driver.closeCount - closes0
+	driver.mu.Unlock()
+
+	if opens != 3 {
+		t.Errorf("opens = %d; want 3", opens)
+	}
+	if closes != 1 {
+		t.Errorf("closes = %d; want 1", closes)
+	}
+}
+
+// golang.org/issue/5323
+func TestStmtCloseDeps(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
+	defer setHookpostCloseConn(nil)
+	setHookpostCloseConn(func(_ *fakeConn, err error) {
+		if err != nil {
+			t.Errorf("Error closing fakeConn: %v", err)
+		}
+	})
+
+	db := newTestDB(t, "magicquery")
+	defer closeDB(t, db)
+
+	driver := db.Driver().(*fakeDriver)
+
+	driver.mu.Lock()
+	opens0 := driver.openCount
+	closes0 := driver.closeCount
+	driver.mu.Unlock()
+	openDelta0 := opens0 - closes0
+
+	stmt, err := db.Prepare("SELECT|magicquery|op|op=?,millis=?")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Start 50 parallel slow queries.
+	const (
+		nquery      = 50
+		sleepMillis = 25
+		nbatch      = 2
+	)
+	var wg sync.WaitGroup
+	for batch := 0; batch < nbatch; batch++ {
+		for i := 0; i < nquery; i++ {
+			wg.Add(1)
+			go func() {
+				defer wg.Done()
+				var op string
+				if err := stmt.QueryRow("sleep", sleepMillis).Scan(&op); err != nil && err != ErrNoRows {
+					t.Error(err)
+				}
+			}()
+		}
+		// Sleep for twice the expected length of time for the
+		// batch of 50 queries above to finish before starting
+		// the next round.
+		time.Sleep(2 * sleepMillis * time.Millisecond)
+	}
+	wg.Wait()
+
+	if g, w := db.numFreeConns(), 2; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	if n := db.numDepsPollUntil(4, time.Second); n > 4 {
+		t.Errorf("number of dependencies = %d; expected <= 4", n)
+		db.dumpDeps(t)
+	}
+
+	driver.mu.Lock()
+	opens := driver.openCount - opens0
+	closes := driver.closeCount - closes0
+	openDelta := (driver.openCount - driver.closeCount) - openDelta0
+	driver.mu.Unlock()
+
+	if openDelta > 2 {
+		t.Logf("open calls = %d", opens)
+		t.Logf("close calls = %d", closes)
+		t.Logf("open delta = %d", openDelta)
+		t.Errorf("db connections opened = %d; want <= 2", openDelta)
+		db.dumpDeps(t)
+	}
+
+	if !waitCondition(5*time.Second, 5*time.Millisecond, func() bool {
+		return len(stmt.css) <= nquery
+	}) {
+		t.Errorf("len(stmt.css) = %d; want <= %d", len(stmt.css), nquery)
+	}
+
+	if err := stmt.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	if g, w := db.numFreeConns(), 2; g != w {
+		t.Errorf("free conns = %d; want %d", g, w)
+	}
+
+	if n := db.numDepsPollUntil(2, time.Second); n > 2 {
+		t.Errorf("number of dependencies = %d; expected <= 2", n)
+		db.dumpDeps(t)
+	}
+
+	db.clearAllConns(t)
+}
+
+// golang.org/issue/5046
+func TestCloseConnBeforeStmts(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	defer setHookpostCloseConn(nil)
+	setHookpostCloseConn(func(_ *fakeConn, err error) {
+		if err != nil {
+			t.Errorf("Error closing fakeConn: %v; from %s", err, stack())
+			db.dumpDeps(t)
+			t.Errorf("DB = %#v", db)
+		}
+	})
+
+	stmt, err := db.Prepare("SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(db.freeConn) != 1 {
+		t.Fatalf("expected 1 freeConn; got %d", len(db.freeConn))
+	}
+	dc := db.freeConn[0]
+	if dc.closed {
+		t.Errorf("conn shouldn't be closed")
+	}
+
+	if n := len(dc.openStmt); n != 1 {
+		t.Errorf("driverConn num openStmt = %d; want 1", n)
+	}
+	err = db.Close()
+	if err != nil {
+		t.Errorf("db Close = %v", err)
+	}
+	if !dc.closed {
+		t.Errorf("after db.Close, driverConn should be closed")
+	}
+	if n := len(dc.openStmt); n != 0 {
+		t.Errorf("driverConn num openStmt = %d; want 0", n)
+	}
+
+	err = stmt.Close()
+	if err != nil {
+		t.Errorf("Stmt close = %v", err)
+	}
+
+	if !dc.closed {
+		t.Errorf("conn should be closed")
+	}
+	if dc.ci != nil {
+		t.Errorf("after Stmt Close, driverConn's Conn interface should be nil")
+	}
+}
+
+// golang.org/issue/5283: don't release the Rows' connection in Close
+// before calling Stmt.Close.
+func TestRowsCloseOrder(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	db.SetMaxIdleConns(0)
+	setStrictFakeConnClose(t)
+	defer setStrictFakeConnClose(nil)
+
+	rows, err := db.Query("SELECT|people|age,name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = rows.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestRowsImplicitClose(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	rows, err := db.Query("SELECT|people|age,name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want, fail := 2, errors.New("fail")
+	r := rows.rowsi.(*rowsCursor)
+	r.errPos, r.err = want, fail
+
+	got := 0
+	for rows.Next() {
+		got++
+	}
+	if got != want {
+		t.Errorf("got %d rows, want %d", got, want)
+	}
+	if err := rows.Err(); err != fail {
+		t.Errorf("got error %v, want %v", err, fail)
+	}
+	if !r.closed {
+		t.Errorf("r.closed is false, want true")
+	}
+}
+
+func TestStmtCloseOrder(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	db.SetMaxIdleConns(0)
+	setStrictFakeConnClose(t)
+	defer setStrictFakeConnClose(nil)
+
+	_, err := db.Query("SELECT|non_existent|name|")
+	if err == nil {
+		t.Fatal("Querying non-existent table should fail")
+	}
+}
+
+// Test cases where there's more than maxBadConnRetries bad connections in the
+// pool (issue 8834)
+func TestManyErrBadConn(t *testing.T) {
+	manyErrBadConnSetup := func(first ...func(db *DB)) *DB {
+		db := newTestDB(t, "people")
+
+		for _, f := range first {
+			f(db)
+		}
+
+		nconn := maxBadConnRetries + 1
+		db.SetMaxIdleConns(nconn)
+		db.SetMaxOpenConns(nconn)
+		// open enough connections
+		func() {
+			for i := 0; i < nconn; i++ {
+				rows, err := db.Query("SELECT|people|age,name|")
+				if err != nil {
+					t.Fatal(err)
+				}
+				defer rows.Close()
+			}
+		}()
+
+		db.mu.Lock()
+		defer db.mu.Unlock()
+		if db.numOpen != nconn {
+			t.Fatalf("unexpected numOpen %d (was expecting %d)", db.numOpen, nconn)
+		} else if len(db.freeConn) != nconn {
+			t.Fatalf("unexpected len(db.freeConn) %d (was expecting %d)", len(db.freeConn), nconn)
+		}
+		for _, conn := range db.freeConn {
+			conn.Lock()
+			conn.ci.(*fakeConn).stickyBad = true
+			conn.Unlock()
+		}
+		return db
+	}
+
+	// Query
+	db := manyErrBadConnSetup()
+	defer closeDB(t, db)
+	rows, err := db.Query("SELECT|people|age,name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = rows.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// Exec
+	db = manyErrBadConnSetup()
+	defer closeDB(t, db)
+	_, err = db.Exec("INSERT|people|name=Julia,age=19")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Begin
+	db = manyErrBadConnSetup()
+	defer closeDB(t, db)
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = tx.Rollback(); err != nil {
+		t.Fatal(err)
+	}
+
+	// Prepare
+	db = manyErrBadConnSetup()
+	defer closeDB(t, db)
+	stmt, err := db.Prepare("SELECT|people|age,name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = stmt.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// Stmt.Exec
+	db = manyErrBadConnSetup(func(db *DB) {
+		stmt, err = db.Prepare("INSERT|people|name=Julia,age=19")
+		if err != nil {
+			t.Fatal(err)
+		}
+	})
+	defer closeDB(t, db)
+	_, err = stmt.Exec()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = stmt.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// Stmt.Query
+	db = manyErrBadConnSetup(func(db *DB) {
+		stmt, err = db.Prepare("SELECT|people|age,name|")
+		if err != nil {
+			t.Fatal(err)
+		}
+	})
+	defer closeDB(t, db)
+	rows, err = stmt.Query()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = rows.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err = stmt.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// Conn
+	db = manyErrBadConnSetup()
+	defer closeDB(t, db)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	conn.dc.ci.(*fakeConn).skipDirtySession = true
+	err = conn.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Ping
+	db = manyErrBadConnSetup()
+	defer closeDB(t, db)
+	err = db.PingContext(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+// Issue 34775: Ensure that a Tx cannot commit after a rollback.
+func TestTxCannotCommitAfterRollback(t *testing.T) {
+	db := newTestDB(t, "tx_status")
+	defer closeDB(t, db)
+
+	// First check query reporting is correct.
+	var txStatus string
+	err := db.QueryRow("SELECT|tx_status|tx_status|").Scan(&txStatus)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if g, w := txStatus, "autocommit"; g != w {
+		t.Fatalf("tx_status=%q, wanted %q", g, w)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Ignore dirty session for this test.
+	// A failing test should trigger the dirty session flag as well,
+	// but that isn't exactly what this should test for.
+	tx.txi.(*fakeTx).c.skipDirtySession = true
+
+	defer tx.Rollback()
+
+	err = tx.QueryRow("SELECT|tx_status|tx_status|").Scan(&txStatus)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if g, w := txStatus, "transaction"; g != w {
+		t.Fatalf("tx_status=%q, wanted %q", g, w)
+	}
+
+	// 1. Begin a transaction.
+	// 2. (A) Start a query, (B) begin Tx rollback through a ctx cancel.
+	// 3. Check if 2.A has committed in Tx (pass) or outside of Tx (fail).
+	sendQuery := make(chan struct{})
+	// The Tx status is returned through the row results, ensure
+	// that the rows results are not cancelled.
+	bypassRowsAwaitDone = true
+	hookTxGrabConn = func() {
+		cancel()
+		<-sendQuery
+	}
+	rollbackHook = func() {
+		close(sendQuery)
+	}
+	defer func() {
+		hookTxGrabConn = nil
+		rollbackHook = nil
+		bypassRowsAwaitDone = false
+	}()
+
+	err = tx.QueryRow("SELECT|tx_status|tx_status|").Scan(&txStatus)
+	if err != nil {
+		// A failure here would be expected if skipDirtySession was not set to true above.
+		t.Fatal(err)
+	}
+	if g, w := txStatus, "transaction"; g != w {
+		t.Fatalf("tx_status=%q, wanted %q", g, w)
+	}
+}
+
+// Issue 40985 transaction statement deadlock while context cancel.
+func TestTxStmtDeadlock(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Millisecond)
+	defer cancel()
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	stmt, err := tx.Prepare("SELECT|people|name,age|age=?")
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Run number of stmt queries to reproduce deadlock from context cancel
+	for i := 0; i < 1e3; i++ {
+		// Encounter any close related errors (e.g. ErrTxDone, stmt is closed)
+		// is expected due to context cancel.
+		_, err = stmt.Query(1)
+		if err != nil {
+			break
+		}
+	}
+	_ = tx.Rollback()
+}
+
+// Issue32530 encounters an issue where a connection may
+// expire right after it comes out of a used connection pool
+// even when a new connection is requested.
+func TestConnExpiresFreshOutOfPool(t *testing.T) {
+	execCases := []struct {
+		expired  bool
+		badReset bool
+	}{
+		{false, false},
+		{true, false},
+		{false, true},
+	}
+
+	t0 := time.Unix(1000000, 0)
+	offset := time.Duration(0)
+	offsetMu := sync.RWMutex{}
+
+	nowFunc = func() time.Time {
+		offsetMu.RLock()
+		defer offsetMu.RUnlock()
+		return t0.Add(offset)
+	}
+	defer func() { nowFunc = time.Now }()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	db := newTestDB(t, "magicquery")
+	defer closeDB(t, db)
+
+	db.SetMaxOpenConns(1)
+
+	for _, ec := range execCases {
+		ec := ec
+		name := fmt.Sprintf("expired=%t,badReset=%t", ec.expired, ec.badReset)
+		t.Run(name, func(t *testing.T) {
+			db.clearAllConns(t)
+
+			db.SetMaxIdleConns(1)
+			db.SetConnMaxLifetime(10 * time.Second)
+
+			conn, err := db.conn(ctx, alwaysNewConn)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			afterPutConn := make(chan struct{})
+			waitingForConn := make(chan struct{})
+
+			go func() {
+				defer close(afterPutConn)
+
+				conn, err := db.conn(ctx, alwaysNewConn)
+				if err == nil {
+					db.putConn(conn, err, false)
+				} else {
+					t.Errorf("db.conn: %v", err)
+				}
+			}()
+			go func() {
+				defer close(waitingForConn)
+
+				for {
+					if t.Failed() {
+						return
+					}
+					db.mu.Lock()
+					ct := len(db.connRequests)
+					db.mu.Unlock()
+					if ct > 0 {
+						return
+					}
+					time.Sleep(10 * time.Millisecond)
+				}
+			}()
+
+			<-waitingForConn
+
+			if t.Failed() {
+				return
+			}
+
+			offsetMu.Lock()
+			if ec.expired {
+				offset = 11 * time.Second
+			} else {
+				offset = time.Duration(0)
+			}
+			offsetMu.Unlock()
+
+			conn.ci.(*fakeConn).stickyBad = ec.badReset
+
+			db.putConn(conn, err, true)
+
+			<-afterPutConn
+		})
+	}
+}
+
+// TestIssue20575 ensures the Rows from query does not block
+// closing a transaction. Ensure Rows is closed while closing a trasaction.
+func TestIssue20575(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	_, err = tx.QueryContext(ctx, "SELECT|people|age,name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Do not close Rows from QueryContext.
+	err = tx.Rollback()
+	if err != nil {
+		t.Fatal(err)
+	}
+	select {
+	default:
+	case <-ctx.Done():
+		t.Fatal("timeout: failed to rollback query without closing rows:", ctx.Err())
+	}
+}
+
+// TestIssue20622 tests closing the transaction before rows is closed, requires
+// the race detector to fail.
+func TestIssue20622(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rows, err := tx.Query("SELECT|people|age,name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	count := 0
+	for rows.Next() {
+		count++
+		var age int
+		var name string
+		if err := rows.Scan(&age, &name); err != nil {
+			t.Fatal("scan failed", err)
+		}
+
+		if count == 1 {
+			cancel()
+		}
+		time.Sleep(100 * time.Millisecond)
+	}
+	rows.Close()
+	tx.Commit()
+}
+
+// golang.org/issue/5718
+func TestErrBadConnReconnect(t *testing.T) {
+	db := newTestDB(t, "foo")
+	defer closeDB(t, db)
+	exec(t, db, "CREATE|t1|name=string,age=int32,dead=bool")
+
+	simulateBadConn := func(name string, hook *func() bool, op func() error) {
+		broken, retried := false, false
+		numOpen := db.numOpen
+
+		// simulate a broken connection on the first try
+		*hook = func() bool {
+			if !broken {
+				broken = true
+				return true
+			}
+			retried = true
+			return false
+		}
+
+		if err := op(); err != nil {
+			t.Errorf(name+": %v", err)
+			return
+		}
+
+		if !broken || !retried {
+			t.Error(name + ": Failed to simulate broken connection")
+		}
+		*hook = nil
+
+		if numOpen != db.numOpen {
+			t.Errorf(name+": leaked %d connection(s)!", db.numOpen-numOpen)
+			numOpen = db.numOpen
+		}
+	}
+
+	// db.Exec
+	dbExec := func() error {
+		_, err := db.Exec("INSERT|t1|name=?,age=?,dead=?", "Gordon", 3, true)
+		return err
+	}
+	simulateBadConn("db.Exec prepare", &hookPrepareBadConn, dbExec)
+	simulateBadConn("db.Exec exec", &hookExecBadConn, dbExec)
+
+	// db.Query
+	dbQuery := func() error {
+		rows, err := db.Query("SELECT|t1|age,name|")
+		if err == nil {
+			err = rows.Close()
+		}
+		return err
+	}
+	simulateBadConn("db.Query prepare", &hookPrepareBadConn, dbQuery)
+	simulateBadConn("db.Query query", &hookQueryBadConn, dbQuery)
+
+	// db.Prepare
+	simulateBadConn("db.Prepare", &hookPrepareBadConn, func() error {
+		stmt, err := db.Prepare("INSERT|t1|name=?,age=?,dead=?")
+		if err != nil {
+			return err
+		}
+		stmt.Close()
+		return nil
+	})
+
+	// Provide a way to force a re-prepare of a statement on next execution
+	forcePrepare := func(stmt *Stmt) {
+		stmt.css = nil
+	}
+
+	// stmt.Exec
+	stmt1, err := db.Prepare("INSERT|t1|name=?,age=?,dead=?")
+	if err != nil {
+		t.Fatalf("prepare: %v", err)
+	}
+	defer stmt1.Close()
+	// make sure we must prepare the stmt first
+	forcePrepare(stmt1)
+
+	stmtExec := func() error {
+		_, err := stmt1.Exec("Gopher", 3, false)
+		return err
+	}
+	simulateBadConn("stmt.Exec prepare", &hookPrepareBadConn, stmtExec)
+	simulateBadConn("stmt.Exec exec", &hookExecBadConn, stmtExec)
+
+	// stmt.Query
+	stmt2, err := db.Prepare("SELECT|t1|age,name|")
+	if err != nil {
+		t.Fatalf("prepare: %v", err)
+	}
+	defer stmt2.Close()
+	// make sure we must prepare the stmt first
+	forcePrepare(stmt2)
+
+	stmtQuery := func() error {
+		rows, err := stmt2.Query()
+		if err == nil {
+			err = rows.Close()
+		}
+		return err
+	}
+	simulateBadConn("stmt.Query prepare", &hookPrepareBadConn, stmtQuery)
+	simulateBadConn("stmt.Query exec", &hookQueryBadConn, stmtQuery)
+}
+
+// golang.org/issue/11264
+func TestTxEndBadConn(t *testing.T) {
+	db := newTestDB(t, "foo")
+	defer closeDB(t, db)
+	db.SetMaxIdleConns(0)
+	exec(t, db, "CREATE|t1|name=string,age=int32,dead=bool")
+	db.SetMaxIdleConns(1)
+
+	simulateBadConn := func(name string, hook *func() bool, op func() error) {
+		broken := false
+		numOpen := db.numOpen
+
+		*hook = func() bool {
+			if !broken {
+				broken = true
+			}
+			return broken
+		}
+
+		if err := op(); err != driver.ErrBadConn {
+			t.Errorf(name+": %v", err)
+			return
+		}
+
+		if !broken {
+			t.Error(name + ": Failed to simulate broken connection")
+		}
+		*hook = nil
+
+		if numOpen != db.numOpen {
+			t.Errorf(name+": leaked %d connection(s)!", db.numOpen-numOpen)
+		}
+	}
+
+	// db.Exec
+	dbExec := func(endTx func(tx *Tx) error) func() error {
+		return func() error {
+			tx, err := db.Begin()
+			if err != nil {
+				return err
+			}
+			_, err = tx.Exec("INSERT|t1|name=?,age=?,dead=?", "Gordon", 3, true)
+			if err != nil {
+				return err
+			}
+			return endTx(tx)
+		}
+	}
+	simulateBadConn("db.Tx.Exec commit", &hookCommitBadConn, dbExec((*Tx).Commit))
+	simulateBadConn("db.Tx.Exec rollback", &hookRollbackBadConn, dbExec((*Tx).Rollback))
+
+	// db.Query
+	dbQuery := func(endTx func(tx *Tx) error) func() error {
+		return func() error {
+			tx, err := db.Begin()
+			if err != nil {
+				return err
+			}
+			rows, err := tx.Query("SELECT|t1|age,name|")
+			if err == nil {
+				err = rows.Close()
+			} else {
+				return err
+			}
+			return endTx(tx)
+		}
+	}
+	simulateBadConn("db.Tx.Query commit", &hookCommitBadConn, dbQuery((*Tx).Commit))
+	simulateBadConn("db.Tx.Query rollback", &hookRollbackBadConn, dbQuery((*Tx).Rollback))
+}
+
+type concurrentTest interface {
+	init(t testing.TB, db *DB)
+	finish(t testing.TB)
+	test(t testing.TB) error
+}
+
+type concurrentDBQueryTest struct {
+	db *DB
+}
+
+func (c *concurrentDBQueryTest) init(t testing.TB, db *DB) {
+	c.db = db
+}
+
+func (c *concurrentDBQueryTest) finish(t testing.TB) {
+	c.db = nil
+}
+
+func (c *concurrentDBQueryTest) test(t testing.TB) error {
+	rows, err := c.db.Query("SELECT|people|name|")
+	if err != nil {
+		t.Error(err)
+		return err
+	}
+	var name string
+	for rows.Next() {
+		rows.Scan(&name)
+	}
+	rows.Close()
+	return nil
+}
+
+type concurrentDBExecTest struct {
+	db *DB
+}
+
+func (c *concurrentDBExecTest) init(t testing.TB, db *DB) {
+	c.db = db
+}
+
+func (c *concurrentDBExecTest) finish(t testing.TB) {
+	c.db = nil
+}
+
+func (c *concurrentDBExecTest) test(t testing.TB) error {
+	_, err := c.db.Exec("NOSERT|people|name=Chris,age=?,photo=CPHOTO,bdate=?", 3, chrisBirthday)
+	if err != nil {
+		t.Error(err)
+		return err
+	}
+	return nil
+}
+
+type concurrentStmtQueryTest struct {
+	db   *DB
+	stmt *Stmt
+}
+
+func (c *concurrentStmtQueryTest) init(t testing.TB, db *DB) {
+	c.db = db
+	var err error
+	c.stmt, err = db.Prepare("SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func (c *concurrentStmtQueryTest) finish(t testing.TB) {
+	if c.stmt != nil {
+		c.stmt.Close()
+		c.stmt = nil
+	}
+	c.db = nil
+}
+
+func (c *concurrentStmtQueryTest) test(t testing.TB) error {
+	rows, err := c.stmt.Query()
+	if err != nil {
+		t.Errorf("error on query:  %v", err)
+		return err
+	}
+
+	var name string
+	for rows.Next() {
+		rows.Scan(&name)
+	}
+	rows.Close()
+	return nil
+}
+
+type concurrentStmtExecTest struct {
+	db   *DB
+	stmt *Stmt
+}
+
+func (c *concurrentStmtExecTest) init(t testing.TB, db *DB) {
+	c.db = db
+	var err error
+	c.stmt, err = db.Prepare("NOSERT|people|name=Chris,age=?,photo=CPHOTO,bdate=?")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func (c *concurrentStmtExecTest) finish(t testing.TB) {
+	if c.stmt != nil {
+		c.stmt.Close()
+		c.stmt = nil
+	}
+	c.db = nil
+}
+
+func (c *concurrentStmtExecTest) test(t testing.TB) error {
+	_, err := c.stmt.Exec(3, chrisBirthday)
+	if err != nil {
+		t.Errorf("error on exec:  %v", err)
+		return err
+	}
+	return nil
+}
+
+type concurrentTxQueryTest struct {
+	db *DB
+	tx *Tx
+}
+
+func (c *concurrentTxQueryTest) init(t testing.TB, db *DB) {
+	c.db = db
+	var err error
+	c.tx, err = c.db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func (c *concurrentTxQueryTest) finish(t testing.TB) {
+	if c.tx != nil {
+		c.tx.Rollback()
+		c.tx = nil
+	}
+	c.db = nil
+}
+
+func (c *concurrentTxQueryTest) test(t testing.TB) error {
+	rows, err := c.db.Query("SELECT|people|name|")
+	if err != nil {
+		t.Error(err)
+		return err
+	}
+	var name string
+	for rows.Next() {
+		rows.Scan(&name)
+	}
+	rows.Close()
+	return nil
+}
+
+type concurrentTxExecTest struct {
+	db *DB
+	tx *Tx
+}
+
+func (c *concurrentTxExecTest) init(t testing.TB, db *DB) {
+	c.db = db
+	var err error
+	c.tx, err = c.db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func (c *concurrentTxExecTest) finish(t testing.TB) {
+	if c.tx != nil {
+		c.tx.Rollback()
+		c.tx = nil
+	}
+	c.db = nil
+}
+
+func (c *concurrentTxExecTest) test(t testing.TB) error {
+	_, err := c.tx.Exec("NOSERT|people|name=Chris,age=?,photo=CPHOTO,bdate=?", 3, chrisBirthday)
+	if err != nil {
+		t.Error(err)
+		return err
+	}
+	return nil
+}
+
+type concurrentTxStmtQueryTest struct {
+	db   *DB
+	tx   *Tx
+	stmt *Stmt
+}
+
+func (c *concurrentTxStmtQueryTest) init(t testing.TB, db *DB) {
+	c.db = db
+	var err error
+	c.tx, err = c.db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	c.stmt, err = c.tx.Prepare("SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func (c *concurrentTxStmtQueryTest) finish(t testing.TB) {
+	if c.stmt != nil {
+		c.stmt.Close()
+		c.stmt = nil
+	}
+	if c.tx != nil {
+		c.tx.Rollback()
+		c.tx = nil
+	}
+	c.db = nil
+}
+
+func (c *concurrentTxStmtQueryTest) test(t testing.TB) error {
+	rows, err := c.stmt.Query()
+	if err != nil {
+		t.Errorf("error on query:  %v", err)
+		return err
+	}
+
+	var name string
+	for rows.Next() {
+		rows.Scan(&name)
+	}
+	rows.Close()
+	return nil
+}
+
+type concurrentTxStmtExecTest struct {
+	db   *DB
+	tx   *Tx
+	stmt *Stmt
+}
+
+func (c *concurrentTxStmtExecTest) init(t testing.TB, db *DB) {
+	c.db = db
+	var err error
+	c.tx, err = c.db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	c.stmt, err = c.tx.Prepare("NOSERT|people|name=Chris,age=?,photo=CPHOTO,bdate=?")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func (c *concurrentTxStmtExecTest) finish(t testing.TB) {
+	if c.stmt != nil {
+		c.stmt.Close()
+		c.stmt = nil
+	}
+	if c.tx != nil {
+		c.tx.Rollback()
+		c.tx = nil
+	}
+	c.db = nil
+}
+
+func (c *concurrentTxStmtExecTest) test(t testing.TB) error {
+	_, err := c.stmt.Exec(3, chrisBirthday)
+	if err != nil {
+		t.Errorf("error on exec:  %v", err)
+		return err
+	}
+	return nil
+}
+
+type concurrentRandomTest struct {
+	tests []concurrentTest
+}
+
+func (c *concurrentRandomTest) init(t testing.TB, db *DB) {
+	c.tests = []concurrentTest{
+		new(concurrentDBQueryTest),
+		new(concurrentDBExecTest),
+		new(concurrentStmtQueryTest),
+		new(concurrentStmtExecTest),
+		new(concurrentTxQueryTest),
+		new(concurrentTxExecTest),
+		new(concurrentTxStmtQueryTest),
+		new(concurrentTxStmtExecTest),
+	}
+	for _, ct := range c.tests {
+		ct.init(t, db)
+	}
+}
+
+func (c *concurrentRandomTest) finish(t testing.TB) {
+	for _, ct := range c.tests {
+		ct.finish(t)
+	}
+}
+
+func (c *concurrentRandomTest) test(t testing.TB) error {
+	ct := c.tests[rand.Intn(len(c.tests))]
+	return ct.test(t)
+}
+
+func doConcurrentTest(t testing.TB, ct concurrentTest) {
+	maxProcs, numReqs := 1, 500
+	if testing.Short() {
+		maxProcs, numReqs = 4, 50
+	}
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(maxProcs))
+
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ct.init(t, db)
+	defer ct.finish(t)
+
+	var wg sync.WaitGroup
+	wg.Add(numReqs)
+
+	reqs := make(chan bool)
+	defer close(reqs)
+
+	for i := 0; i < maxProcs*2; i++ {
+		go func() {
+			for range reqs {
+				err := ct.test(t)
+				if err != nil {
+					wg.Done()
+					continue
+				}
+				wg.Done()
+			}
+		}()
+	}
+
+	for i := 0; i < numReqs; i++ {
+		reqs <- true
+	}
+
+	wg.Wait()
+}
+
+func TestIssue6081(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	drv := db.Driver().(*fakeDriver)
+	drv.mu.Lock()
+	opens0 := drv.openCount
+	closes0 := drv.closeCount
+	drv.mu.Unlock()
+
+	stmt, err := db.Prepare("SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	setRowsCloseHook(func(rows *Rows, err *error) {
+		*err = driver.ErrBadConn
+	})
+	defer setRowsCloseHook(nil)
+	for i := 0; i < 10; i++ {
+		rows, err := stmt.Query()
+		if err != nil {
+			t.Fatal(err)
+		}
+		rows.Close()
+	}
+	if n := len(stmt.css); n > 1 {
+		t.Errorf("len(css slice) = %d; want <= 1", n)
+	}
+	stmt.Close()
+	if n := len(stmt.css); n != 0 {
+		t.Errorf("len(css slice) after Close = %d; want 0", n)
+	}
+
+	drv.mu.Lock()
+	opens := drv.openCount - opens0
+	closes := drv.closeCount - closes0
+	drv.mu.Unlock()
+	if opens < 9 {
+		t.Errorf("opens = %d; want >= 9", opens)
+	}
+	if closes < 9 {
+		t.Errorf("closes = %d; want >= 9", closes)
+	}
+}
+
+// TestIssue18429 attempts to stress rolling back the transaction from a
+// context cancel while simultaneously calling Tx.Rollback. Rolling back from a
+// context happens concurrently so tx.rollback and tx.Commit must guard against
+// double entry.
+//
+// In the test, a context is canceled while the query is in process so
+// the internal rollback will run concurrently with the explicitly called
+// Tx.Rollback.
+//
+// The addition of calling rows.Next also tests
+// Issue 21117.
+func TestIssue18429(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx := context.Background()
+	sem := make(chan bool, 20)
+	var wg sync.WaitGroup
+
+	const milliWait = 30
+
+	for i := 0; i < 100; i++ {
+		sem <- true
+		wg.Add(1)
+		go func() {
+			defer func() {
+				<-sem
+				wg.Done()
+			}()
+			qwait := (time.Duration(rand.Intn(milliWait)) * time.Millisecond).String()
+
+			ctx, cancel := context.WithTimeout(ctx, time.Duration(rand.Intn(milliWait))*time.Millisecond)
+			defer cancel()
+
+			tx, err := db.BeginTx(ctx, nil)
+			if err != nil {
+				return
+			}
+			// This is expected to give a cancel error most, but not all the time.
+			// Test failure will happen with a panic or other race condition being
+			// reported.
+			rows, _ := tx.QueryContext(ctx, "WAIT|"+qwait+"|SELECT|people|name|")
+			if rows != nil {
+				var name string
+				// Call Next to test Issue 21117 and check for races.
+				for rows.Next() {
+					// Scan the buffer so it is read and checked for races.
+					rows.Scan(&name)
+				}
+				rows.Close()
+			}
+			// This call will race with the context cancel rollback to complete
+			// if the rollback itself isn't guarded.
+			tx.Rollback()
+		}()
+	}
+	wg.Wait()
+}
+
+// TestIssue20160 attempts to test a short context life on a stmt Query.
+func TestIssue20160(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx := context.Background()
+	sem := make(chan bool, 20)
+	var wg sync.WaitGroup
+
+	const milliWait = 30
+
+	stmt, err := db.PrepareContext(ctx, "SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer stmt.Close()
+
+	for i := 0; i < 100; i++ {
+		sem <- true
+		wg.Add(1)
+		go func() {
+			defer func() {
+				<-sem
+				wg.Done()
+			}()
+			ctx, cancel := context.WithTimeout(ctx, time.Duration(rand.Intn(milliWait))*time.Millisecond)
+			defer cancel()
+
+			// This is expected to give a cancel error most, but not all the time.
+			// Test failure will happen with a panic or other race condition being
+			// reported.
+			rows, _ := stmt.QueryContext(ctx)
+			if rows != nil {
+				rows.Close()
+			}
+		}()
+	}
+	wg.Wait()
+}
+
+// TestIssue18719 closes the context right before use. The sql.driverConn
+// will nil out the ci on close in a lock, but if another process uses it right after
+// it will panic with on the nil ref.
+//
+// See https://golang.org/cl/35550 .
+func TestIssue18719(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	hookTxGrabConn = func() {
+		cancel()
+
+		// Wait for the context to cancel and tx to rollback.
+		for tx.isDone() == false {
+			time.Sleep(3 * time.Millisecond)
+		}
+	}
+	defer func() { hookTxGrabConn = nil }()
+
+	// This call will grab the connection and cancel the context
+	// after it has done so. Code after must deal with the canceled state.
+	_, err = tx.QueryContext(ctx, "SELECT|people|name|")
+	if err != nil {
+		t.Fatalf("expected error %v but got %v", nil, err)
+	}
+
+	// Rows may be ignored because it will be closed when the context is canceled.
+
+	// Do not explicitly rollback. The rollback will happen from the
+	// canceled context.
+
+	cancel()
+}
+
+func TestIssue20647(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	conn.dc.ci.(*fakeConn).skipDirtySession = true
+	defer conn.Close()
+
+	stmt, err := conn.PrepareContext(ctx, "SELECT|people|name|")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer stmt.Close()
+
+	rows1, err := stmt.QueryContext(ctx)
+	if err != nil {
+		t.Fatal("rows1", err)
+	}
+	defer rows1.Close()
+
+	rows2, err := stmt.QueryContext(ctx)
+	if err != nil {
+		t.Fatal("rows2", err)
+	}
+	defer rows2.Close()
+
+	if rows1.dc != rows2.dc {
+		t.Fatal("stmt prepared on Conn does not use same connection")
+	}
+}
+
+func TestConcurrency(t *testing.T) {
+	list := []struct {
+		name string
+		ct   concurrentTest
+	}{
+		{"Query", new(concurrentDBQueryTest)},
+		{"Exec", new(concurrentDBExecTest)},
+		{"StmtQuery", new(concurrentStmtQueryTest)},
+		{"StmtExec", new(concurrentStmtExecTest)},
+		{"TxQuery", new(concurrentTxQueryTest)},
+		{"TxExec", new(concurrentTxExecTest)},
+		{"TxStmtQuery", new(concurrentTxStmtQueryTest)},
+		{"TxStmtExec", new(concurrentTxStmtExecTest)},
+		{"Random", new(concurrentRandomTest)},
+	}
+	for _, item := range list {
+		t.Run(item.name, func(t *testing.T) {
+			doConcurrentTest(t, item.ct)
+		})
+	}
+}
+
+func TestConnectionLeak(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	// Start by opening defaultMaxIdleConns
+	rows := make([]*Rows, defaultMaxIdleConns)
+	// We need to SetMaxOpenConns > MaxIdleConns, so the DB can open
+	// a new connection and we can fill the idle queue with the released
+	// connections.
+	db.SetMaxOpenConns(len(rows) + 1)
+	for ii := range rows {
+		r, err := db.Query("SELECT|people|name|")
+		if err != nil {
+			t.Fatal(err)
+		}
+		r.Next()
+		if err := r.Err(); err != nil {
+			t.Fatal(err)
+		}
+		rows[ii] = r
+	}
+	// Now we have defaultMaxIdleConns busy connections. Open
+	// a new one, but wait until the busy connections are released
+	// before returning control to DB.
+	drv := db.Driver().(*fakeDriver)
+	drv.waitCh = make(chan struct{}, 1)
+	drv.waitingCh = make(chan struct{}, 1)
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		r, err := db.Query("SELECT|people|name|")
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		r.Close()
+		wg.Done()
+	}()
+	// Wait until the goroutine we've just created has started waiting.
+	<-drv.waitingCh
+	// Now close the busy connections. This provides a connection for
+	// the blocked goroutine and then fills up the idle queue.
+	for _, v := range rows {
+		v.Close()
+	}
+	// At this point we give the new connection to DB. This connection is
+	// now useless, since the idle queue is full and there are no pending
+	// requests. DB should deal with this situation without leaking the
+	// connection.
+	drv.waitCh <- struct{}{}
+	wg.Wait()
+}
+
+func TestStatsMaxIdleClosedZero(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	db.SetMaxOpenConns(1)
+	db.SetMaxIdleConns(1)
+	db.SetConnMaxLifetime(0)
+
+	preMaxIdleClosed := db.Stats().MaxIdleClosed
+
+	for i := 0; i < 10; i++ {
+		rows, err := db.Query("SELECT|people|name|")
+		if err != nil {
+			t.Fatal(err)
+		}
+		rows.Close()
+	}
+
+	st := db.Stats()
+	maxIdleClosed := st.MaxIdleClosed - preMaxIdleClosed
+	t.Logf("MaxIdleClosed: %d", maxIdleClosed)
+	if maxIdleClosed != 0 {
+		t.Fatal("expected 0 max idle closed conns, got: ", maxIdleClosed)
+	}
+}
+
+func TestStatsMaxIdleClosedTen(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	db.SetMaxOpenConns(1)
+	db.SetMaxIdleConns(0)
+	db.SetConnMaxLifetime(0)
+
+	preMaxIdleClosed := db.Stats().MaxIdleClosed
+
+	for i := 0; i < 10; i++ {
+		rows, err := db.Query("SELECT|people|name|")
+		if err != nil {
+			t.Fatal(err)
+		}
+		rows.Close()
+	}
+
+	st := db.Stats()
+	maxIdleClosed := st.MaxIdleClosed - preMaxIdleClosed
+	t.Logf("MaxIdleClosed: %d", maxIdleClosed)
+	if maxIdleClosed != 10 {
+		t.Fatal("expected 0 max idle closed conns, got: ", maxIdleClosed)
+	}
+}
+
+func TestMaxIdleTime(t *testing.T) {
+	list := []struct {
+		wantMaxIdleTime time.Duration
+		wantIdleClosed  int64
+		timeOffset      time.Duration
+	}{
+		{time.Nanosecond, 1, 10 * time.Millisecond},
+		{time.Hour, 0, 10 * time.Millisecond},
+	}
+	baseTime := time.Unix(0, 0)
+	defer func() {
+		nowFunc = time.Now
+	}()
+	for _, item := range list {
+		nowFunc = func() time.Time {
+			return baseTime
+		}
+		t.Run(fmt.Sprintf("%v", item.wantMaxIdleTime), func(t *testing.T) {
+			db := newTestDB(t, "people")
+			defer closeDB(t, db)
+
+			db.SetMaxOpenConns(1)
+			db.SetMaxIdleConns(1)
+			db.SetConnMaxIdleTime(item.wantMaxIdleTime)
+			db.SetConnMaxLifetime(0)
+
+			preMaxIdleClosed := db.Stats().MaxIdleTimeClosed
+
+			if err := db.Ping(); err != nil {
+				t.Fatal(err)
+			}
+
+			nowFunc = func() time.Time {
+				return baseTime.Add(item.timeOffset)
+			}
+
+			db.mu.Lock()
+			closing := db.connectionCleanerRunLocked()
+			db.mu.Unlock()
+			for _, c := range closing {
+				c.Close()
+			}
+			if g, w := int64(len(closing)), item.wantIdleClosed; g != w {
+				t.Errorf("got: %d; want %d closed conns", g, w)
+			}
+
+			st := db.Stats()
+			maxIdleClosed := st.MaxIdleTimeClosed - preMaxIdleClosed
+			if g, w := maxIdleClosed, item.wantIdleClosed; g != w {
+				t.Errorf(" got: %d; want %d max idle closed conns", g, w)
+			}
+		})
+	}
+}
+
+type nvcDriver struct {
+	fakeDriver
+	skipNamedValueCheck bool
+}
+
+func (d *nvcDriver) Open(dsn string) (driver.Conn, error) {
+	c, err := d.fakeDriver.Open(dsn)
+	fc := c.(*fakeConn)
+	fc.db.allowAny = true
+	return &nvcConn{fc, d.skipNamedValueCheck}, err
+}
+
+type nvcConn struct {
+	*fakeConn
+	skipNamedValueCheck bool
+}
+
+type decimalInt struct {
+	value int
+}
+
+type doNotInclude struct{}
+
+var _ driver.NamedValueChecker = &nvcConn{}
+
+func (c *nvcConn) CheckNamedValue(nv *driver.NamedValue) error {
+	if c.skipNamedValueCheck {
+		return driver.ErrSkip
+	}
+	switch v := nv.Value.(type) {
+	default:
+		return driver.ErrSkip
+	case Out:
+		switch ov := v.Dest.(type) {
+		default:
+			return errors.New("unknown NameValueCheck OUTPUT type")
+		case *string:
+			*ov = "from-server"
+			nv.Value = "OUT:*string"
+		}
+		return nil
+	case decimalInt, []int64:
+		return nil
+	case doNotInclude:
+		return driver.ErrRemoveArgument
+	}
+}
+
+func TestNamedValueChecker(t *testing.T) {
+	Register("NamedValueCheck", &nvcDriver{})
+	db, err := Open("NamedValueCheck", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	_, err = db.ExecContext(ctx, "WIPE")
+	if err != nil {
+		t.Fatal("exec wipe", err)
+	}
+
+	_, err = db.ExecContext(ctx, "CREATE|keys|dec1=any,str1=string,out1=string,array1=any")
+	if err != nil {
+		t.Fatal("exec create", err)
+	}
+
+	o1 := ""
+	_, err = db.ExecContext(ctx, "INSERT|keys|dec1=?A,str1=?,out1=?O1,array1=?", Named("A", decimalInt{123}), "hello", Named("O1", Out{Dest: &o1}), []int64{42, 128, 707}, doNotInclude{})
+	if err != nil {
+		t.Fatal("exec insert", err)
+	}
+	var (
+		str1 string
+		dec1 decimalInt
+		arr1 []int64
+	)
+	err = db.QueryRowContext(ctx, "SELECT|keys|dec1,str1,array1|").Scan(&dec1, &str1, &arr1)
+	if err != nil {
+		t.Fatal("select", err)
+	}
+
+	list := []struct{ got, want interface{} }{
+		{o1, "from-server"},
+		{dec1, decimalInt{123}},
+		{str1, "hello"},
+		{arr1, []int64{42, 128, 707}},
+	}
+
+	for index, item := range list {
+		if !reflect.DeepEqual(item.got, item.want) {
+			t.Errorf("got %#v wanted %#v for index %d", item.got, item.want, index)
+		}
+	}
+}
+
+func TestNamedValueCheckerSkip(t *testing.T) {
+	Register("NamedValueCheckSkip", &nvcDriver{skipNamedValueCheck: true})
+	db, err := Open("NamedValueCheckSkip", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	_, err = db.ExecContext(ctx, "WIPE")
+	if err != nil {
+		t.Fatal("exec wipe", err)
+	}
+
+	_, err = db.ExecContext(ctx, "CREATE|keys|dec1=any")
+	if err != nil {
+		t.Fatal("exec create", err)
+	}
+
+	_, err = db.ExecContext(ctx, "INSERT|keys|dec1=?A", Named("A", decimalInt{123}))
+	if err == nil {
+		t.Fatalf("expected error with bad argument, got %v", err)
+	}
+}
+
+func TestOpenConnector(t *testing.T) {
+	Register("testctx", &fakeDriverCtx{})
+	db, err := Open("testctx", "people")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	if _, is := db.connector.(*fakeConnector); !is {
+		t.Fatal("not using *fakeConnector")
+	}
+}
+
+type ctxOnlyDriver struct {
+	fakeDriver
+}
+
+func (d *ctxOnlyDriver) Open(dsn string) (driver.Conn, error) {
+	conn, err := d.fakeDriver.Open(dsn)
+	if err != nil {
+		return nil, err
+	}
+	return &ctxOnlyConn{fc: conn.(*fakeConn)}, nil
+}
+
+var (
+	_ driver.Conn           = &ctxOnlyConn{}
+	_ driver.QueryerContext = &ctxOnlyConn{}
+	_ driver.ExecerContext  = &ctxOnlyConn{}
+)
+
+type ctxOnlyConn struct {
+	fc *fakeConn
+
+	queryCtxCalled bool
+	execCtxCalled  bool
+}
+
+func (c *ctxOnlyConn) Begin() (driver.Tx, error) {
+	return c.fc.Begin()
+}
+
+func (c *ctxOnlyConn) Close() error {
+	return c.fc.Close()
+}
+
+// Prepare is still part of the Conn interface, so while it isn't used
+// must be defined for compatibility.
+func (c *ctxOnlyConn) Prepare(q string) (driver.Stmt, error) {
+	panic("not used")
+}
+
+func (c *ctxOnlyConn) PrepareContext(ctx context.Context, q string) (driver.Stmt, error) {
+	return c.fc.PrepareContext(ctx, q)
+}
+
+func (c *ctxOnlyConn) QueryContext(ctx context.Context, q string, args []driver.NamedValue) (driver.Rows, error) {
+	c.queryCtxCalled = true
+	return c.fc.QueryContext(ctx, q, args)
+}
+
+func (c *ctxOnlyConn) ExecContext(ctx context.Context, q string, args []driver.NamedValue) (driver.Result, error) {
+	c.execCtxCalled = true
+	return c.fc.ExecContext(ctx, q, args)
+}
+
+// TestQueryExecContextOnly ensures drivers only need to implement QueryContext
+// and ExecContext methods.
+func TestQueryExecContextOnly(t *testing.T) {
+	// Ensure connection does not implement non-context interfaces.
+	var connType driver.Conn = &ctxOnlyConn{}
+	if _, ok := connType.(driver.Execer); ok {
+		t.Fatalf("%T must not implement driver.Execer", connType)
+	}
+	if _, ok := connType.(driver.Queryer); ok {
+		t.Fatalf("%T must not implement driver.Queryer", connType)
+	}
+
+	Register("ContextOnly", &ctxOnlyDriver{})
+	db, err := Open("ContextOnly", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatal("db.Conn", err)
+	}
+	defer conn.Close()
+	coc := conn.dc.ci.(*ctxOnlyConn)
+	coc.fc.skipDirtySession = true
+
+	_, err = conn.ExecContext(ctx, "WIPE")
+	if err != nil {
+		t.Fatal("exec wipe", err)
+	}
+
+	_, err = conn.ExecContext(ctx, "CREATE|keys|v1=string")
+	if err != nil {
+		t.Fatal("exec create", err)
+	}
+	expectedValue := "value1"
+	_, err = conn.ExecContext(ctx, "INSERT|keys|v1=?", expectedValue)
+	if err != nil {
+		t.Fatal("exec insert", err)
+	}
+	rows, err := conn.QueryContext(ctx, "SELECT|keys|v1|")
+	if err != nil {
+		t.Fatal("query select", err)
+	}
+	v1 := ""
+	for rows.Next() {
+		err = rows.Scan(&v1)
+		if err != nil {
+			t.Fatal("rows scan", err)
+		}
+	}
+	rows.Close()
+
+	if v1 != expectedValue {
+		t.Fatalf("expected %q, got %q", expectedValue, v1)
+	}
+
+	if !coc.execCtxCalled {
+		t.Error("ExecContext not called")
+	}
+	if !coc.queryCtxCalled {
+		t.Error("QueryContext not called")
+	}
+}
+
+type alwaysErrScanner struct{}
+
+var errTestScanWrap = errors.New("errTestScanWrap")
+
+func (alwaysErrScanner) Scan(interface{}) error {
+	return errTestScanWrap
+}
+
+// Issue 38099: Ensure that Rows.Scan properly wraps underlying errors.
+func TestRowsScanProperlyWrapsErrors(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	rows, err := db.Query("SELECT|people|age|")
+	if err != nil {
+		t.Fatalf("Query: %v", err)
+	}
+
+	var res alwaysErrScanner
+
+	for rows.Next() {
+		err = rows.Scan(&res)
+		if err == nil {
+			t.Fatal("expecting back an error")
+		}
+		if !errors.Is(err, errTestScanWrap) {
+			t.Fatalf("errors.Is mismatch\n%v\nWant: %v", err, errTestScanWrap)
+		}
+		// Ensure that error substring matching still correctly works.
+		if !strings.Contains(err.Error(), errTestScanWrap.Error()) {
+			t.Fatalf("Error %v does not contain %v", err, errTestScanWrap)
+		}
+	}
+}
+
+// badConn implements a bad driver.Conn, for TestBadDriver.
+// The Exec method panics.
+type badConn struct{}
+
+func (bc badConn) Prepare(query string) (driver.Stmt, error) {
+	return nil, errors.New("badConn Prepare")
+}
+
+func (bc badConn) Close() error {
+	return nil
+}
+
+func (bc badConn) Begin() (driver.Tx, error) {
+	return nil, errors.New("badConn Begin")
+}
+
+func (bc badConn) Exec(query string, args []driver.Value) (driver.Result, error) {
+	panic("badConn.Exec")
+}
+
+// badDriver is a driver.Driver that uses badConn.
+type badDriver struct{}
+
+func (bd badDriver) Open(name string) (driver.Conn, error) {
+	return badConn{}, nil
+}
+
+// Issue 15901.
+func TestBadDriver(t *testing.T) {
+	Register("bad", badDriver{})
+	db, err := Open("bad", "ignored")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		if r := recover(); r == nil {
+			t.Error("expected panic")
+		} else {
+			if want := "badConn.Exec"; r.(string) != want {
+				t.Errorf("panic was %v, expected %v", r, want)
+			}
+		}
+	}()
+	defer db.Close()
+	db.Exec("ignored")
+}
+
+type pingDriver struct {
+	fails bool
+}
+
+type pingConn struct {
+	badConn
+	driver *pingDriver
+}
+
+var pingError = errors.New("Ping failed")
+
+func (pc pingConn) Ping(ctx context.Context) error {
+	if pc.driver.fails {
+		return pingError
+	}
+	return nil
+}
+
+var _ driver.Pinger = pingConn{}
+
+func (pd *pingDriver) Open(name string) (driver.Conn, error) {
+	return pingConn{driver: pd}, nil
+}
+
+func TestPing(t *testing.T) {
+	driver := &pingDriver{}
+	Register("ping", driver)
+
+	db, err := Open("ping", "ignored")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := db.Ping(); err != nil {
+		t.Errorf("err was %#v, expected nil", err)
+		return
+	}
+
+	driver.fails = true
+	if err := db.Ping(); err != pingError {
+		t.Errorf("err was %#v, expected pingError", err)
+	}
+}
+
+// Issue 18101.
+func TestTypedString(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+
+	type Str string
+	var scanned Str
+
+	err := db.QueryRow("SELECT|people|name|name=?", "Alice").Scan(&scanned)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected := Str("Alice")
+	if scanned != expected {
+		t.Errorf("expected %+v, got %+v", expected, scanned)
+	}
+}
+
+func BenchmarkConcurrentDBExec(b *testing.B) {
+	b.ReportAllocs()
+	ct := new(concurrentDBExecTest)
+	for i := 0; i < b.N; i++ {
+		doConcurrentTest(b, ct)
+	}
+}
+
+func BenchmarkConcurrentStmtQuery(b *testing.B) {
+	b.ReportAllocs()
+	ct := new(concurrentStmtQueryTest)
+	for i := 0; i < b.N; i++ {
+		doConcurrentTest(b, ct)
+	}
+}
+
+func BenchmarkConcurrentStmtExec(b *testing.B) {
+	b.ReportAllocs()
+	ct := new(concurrentStmtExecTest)
+	for i := 0; i < b.N; i++ {
+		doConcurrentTest(b, ct)
+	}
+}
+
+func BenchmarkConcurrentTxQuery(b *testing.B) {
+	b.ReportAllocs()
+	ct := new(concurrentTxQueryTest)
+	for i := 0; i < b.N; i++ {
+		doConcurrentTest(b, ct)
+	}
+}
+
+func BenchmarkConcurrentTxExec(b *testing.B) {
+	b.ReportAllocs()
+	ct := new(concurrentTxExecTest)
+	for i := 0; i < b.N; i++ {
+		doConcurrentTest(b, ct)
+	}
+}
+
+func BenchmarkConcurrentTxStmtQuery(b *testing.B) {
+	b.ReportAllocs()
+	ct := new(concurrentTxStmtQueryTest)
+	for i := 0; i < b.N; i++ {
+		doConcurrentTest(b, ct)
+	}
+}
+
+func BenchmarkConcurrentTxStmtExec(b *testing.B) {
+	b.ReportAllocs()
+	ct := new(concurrentTxStmtExecTest)
+	for i := 0; i < b.N; i++ {
+		doConcurrentTest(b, ct)
+	}
+}
+
+func BenchmarkConcurrentRandom(b *testing.B) {
+	b.ReportAllocs()
+	ct := new(concurrentRandomTest)
+	for i := 0; i < b.N; i++ {
+		doConcurrentTest(b, ct)
+	}
+}
+
+func BenchmarkManyConcurrentQueries(b *testing.B) {
+	b.ReportAllocs()
+	// To see lock contention in Go 1.4, 16~ cores and 128~ goroutines are required.
+	const parallelism = 16
+
+	db := newTestDB(b, "magicquery")
+	defer closeDB(b, db)
+	db.SetMaxIdleConns(runtime.GOMAXPROCS(0) * parallelism)
+
+	stmt, err := db.Prepare("SELECT|magicquery|op|op=?,millis=?")
+	if err != nil {
+		b.Fatal(err)
+	}
+	defer stmt.Close()
+
+	b.SetParallelism(parallelism)
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			rows, err := stmt.Query("sleep", 1)
+			if err != nil {
+				b.Error(err)
+				return
+			}
+			rows.Close()
+		}
+	})
+}