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authorhiddenpath <hiddenpath@yandex-team.com>2024-04-02 23:50:23 +0300
committerhiddenpath <hiddenpath@yandex-team.com>2024-04-03 00:02:31 +0300
commit8923c6d2c438e0aeed2e06b8b0275e1864eeee33 (patch)
tree6b5e476699fc0be5091cb650654ef5f602c8afff /contrib/go/_std_1.22/src/database/sql/driver/driver.go
parentd18afd09df2a08cd023012593b46109b77713a6c (diff)
downloadydb-8923c6d2c438e0aeed2e06b8b0275e1864eeee33.tar.gz
Update golang to 1.22.1
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+// 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 the [database/sql] package.
+//
+// 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.
+//
+// If a [Conn] implements [Validator], then the IsValid method is called
+// before returning the connection to the connection pool. If an entry in the
+// connection pool implements [SessionResetter], then ResetSession
+// is called before reusing the connection for another query. If a connection is
+// never returned to the connection pool but is 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 any
+
+// 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 [database/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 [database/sql.OpenDB], to allow drivers
+// to implement their own [database/sql.DB] constructors, or returned by
+// [DriverContext]'s OpenConnector method, to allow drivers
+// access to context and to avoid repeated parsing of driver
+// configuration.
+//
+// If a Connector implements [io.Closer], the [database/sql.DB.Close]
+// method will call the Close method and return error (if any).
+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 [database/sql]
+// package that a driver.[Conn] is in a bad state (such as the server
+// having earlier closed the connection) and the [database/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.
+//
+// Errors will be checked using [errors.Is]. An error may
+// wrap ErrBadConn or implement the Is(error) bool method.
+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 [database/sql.DB.Ping] and
+// [database/sql.DB.PingContext] will check if there is at least one [Conn] available.
+//
+// If Conn.Ping returns [ErrBadConn], [database/sql.DB.Ping] and [database/sql.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 [database/sql.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 [database/sql.DB.Exec]
+// will fall back to [Execer]; if the Conn does not implement Execer either,
+// [database/sql.DB.Exec] will first prepare a query, execute the statement, and then
+// close the statement.
+//
+// ExecContext may return [ErrSkip].
+//
+// ExecContext 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 [database/sql.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 [database/sql.DB.Query]
+// will fall back to [Queryer]; if the [Conn] does not implement [Queryer] either,
+// [database/sql.DB.Query] will first prepare a query, execute the statement, and then
+// close the statement.
+//
+// QueryContext may return [ErrSkip].
+//
+// QueryContext 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 [database/sql.IsolationLevel] along
+// with any values defined on it.
+type IsolationLevel int
+
+// TxOptions holds the transaction options.
+//
+// This type should be considered identical to [database/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
+// [database/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
+// [Value] types allowed.
+//
+// The [database/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")
+}