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|
package pq
import (
"context"
"database/sql"
"database/sql/driver"
"fmt"
"io"
"io/ioutil"
"time"
)
const (
watchCancelDialContextTimeout = time.Second * 10
)
// Implement the "QueryerContext" interface
func (cn *conn) QueryContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Rows, error) {
list := make([]driver.Value, len(args))
for i, nv := range args {
list[i] = nv.Value
}
finish := cn.watchCancel(ctx)
r, err := cn.query(query, list)
if err != nil {
if finish != nil {
finish()
}
return nil, err
}
r.finish = finish
return r, nil
}
// Implement the "ExecerContext" interface
func (cn *conn) ExecContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Result, error) {
list := make([]driver.Value, len(args))
for i, nv := range args {
list[i] = nv.Value
}
if finish := cn.watchCancel(ctx); finish != nil {
defer finish()
}
return cn.Exec(query, list)
}
// Implement the "ConnPrepareContext" interface
func (cn *conn) PrepareContext(ctx context.Context, query string) (driver.Stmt, error) {
if finish := cn.watchCancel(ctx); finish != nil {
defer finish()
}
return cn.Prepare(query)
}
// Implement the "ConnBeginTx" interface
func (cn *conn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, error) {
var mode string
switch sql.IsolationLevel(opts.Isolation) {
case sql.LevelDefault:
// Don't touch mode: use the server's default
case sql.LevelReadUncommitted:
mode = " ISOLATION LEVEL READ UNCOMMITTED"
case sql.LevelReadCommitted:
mode = " ISOLATION LEVEL READ COMMITTED"
case sql.LevelRepeatableRead:
mode = " ISOLATION LEVEL REPEATABLE READ"
case sql.LevelSerializable:
mode = " ISOLATION LEVEL SERIALIZABLE"
default:
return nil, fmt.Errorf("pq: isolation level not supported: %d", opts.Isolation)
}
if opts.ReadOnly {
mode += " READ ONLY"
} else {
mode += " READ WRITE"
}
tx, err := cn.begin(mode)
if err != nil {
return nil, err
}
cn.txnFinish = cn.watchCancel(ctx)
return tx, nil
}
func (cn *conn) Ping(ctx context.Context) error {
if finish := cn.watchCancel(ctx); finish != nil {
defer finish()
}
rows, err := cn.simpleQuery(";")
if err != nil {
return driver.ErrBadConn // https://golang.org/pkg/database/sql/driver/#Pinger
}
rows.Close()
return nil
}
func (cn *conn) watchCancel(ctx context.Context) func() {
if done := ctx.Done(); done != nil {
finished := make(chan struct{}, 1)
go func() {
select {
case <-done:
select {
case finished <- struct{}{}:
default:
// We raced with the finish func, let the next query handle this with the
// context.
return
}
// Set the connection state to bad so it does not get reused.
cn.err.set(ctx.Err())
// At this point the function level context is canceled,
// so it must not be used for the additional network
// request to cancel the query.
// Create a new context to pass into the dial.
ctxCancel, cancel := context.WithTimeout(context.Background(), watchCancelDialContextTimeout)
defer cancel()
_ = cn.cancel(ctxCancel)
case <-finished:
}
}()
return func() {
select {
case <-finished:
cn.err.set(ctx.Err())
cn.Close()
case finished <- struct{}{}:
}
}
}
return nil
}
func (cn *conn) cancel(ctx context.Context) error {
// Create a new values map (copy). This makes sure the connection created
// in this method cannot write to the same underlying data, which could
// cause a concurrent map write panic. This is necessary because cancel
// is called from a goroutine in watchCancel.
o := make(values)
for k, v := range cn.opts {
o[k] = v
}
c, err := dial(ctx, cn.dialer, o)
if err != nil {
return err
}
defer c.Close()
{
can := conn{
c: c,
}
err = can.ssl(o)
if err != nil {
return err
}
w := can.writeBuf(0)
w.int32(80877102) // cancel request code
w.int32(cn.processID)
w.int32(cn.secretKey)
if err := can.sendStartupPacket(w); err != nil {
return err
}
}
// Read until EOF to ensure that the server received the cancel.
{
_, err := io.Copy(ioutil.Discard, c)
return err
}
}
// Implement the "StmtQueryContext" interface
func (st *stmt) QueryContext(ctx context.Context, args []driver.NamedValue) (driver.Rows, error) {
list := make([]driver.Value, len(args))
for i, nv := range args {
list[i] = nv.Value
}
finish := st.watchCancel(ctx)
r, err := st.query(list)
if err != nil {
if finish != nil {
finish()
}
return nil, err
}
r.finish = finish
return r, nil
}
// Implement the "StmtExecContext" interface
func (st *stmt) ExecContext(ctx context.Context, args []driver.NamedValue) (driver.Result, error) {
list := make([]driver.Value, len(args))
for i, nv := range args {
list[i] = nv.Value
}
if finish := st.watchCancel(ctx); finish != nil {
defer finish()
}
return st.Exec(list)
}
// watchCancel is implemented on stmt in order to not mark the parent conn as bad
func (st *stmt) watchCancel(ctx context.Context) func() {
if done := ctx.Done(); done != nil {
finished := make(chan struct{})
go func() {
select {
case <-done:
// At this point the function level context is canceled,
// so it must not be used for the additional network
// request to cancel the query.
// Create a new context to pass into the dial.
ctxCancel, cancel := context.WithTimeout(context.Background(), watchCancelDialContextTimeout)
defer cancel()
_ = st.cancel(ctxCancel)
finished <- struct{}{}
case <-finished:
}
}()
return func() {
select {
case <-finished:
case finished <- struct{}{}:
}
}
}
return nil
}
func (st *stmt) cancel(ctx context.Context) error {
return st.cn.cancel(ctx)
}
|
