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| -rw-r--r-- | src/database/sql/driver/driver.go | 544 |
1 files changed, 544 insertions, 0 deletions
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") +} |