Package driver

import "database/sql/driver"
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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.

Variables

Bool is a ValueConverter that converts input values to bool.

The conversion rules are: 

var Bool boolType

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, defaultConverter.ConvertValue returns a nil Value. If the argument is a non-nil pointer, it is dereferenced and defaultConverter.ConvertValue is called recursively. Other types are an error. 

var DefaultParameterConverter defaultConverter

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")

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")

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")

Int32 is a ValueConverter that converts input values to int64, respecting the limits of an int32 value. 

var Int32 int32Type

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

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

func IsScanValue 

func IsScanValue(v any) bool

IsScanValue is equivalent to IsValue. It exists for compatibility.

func IsValue 

func IsValue(v any) bool

IsValue reports whether v is a valid Value parameter type.

type ColumnConverter

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, [DefaultParameterConverter]
    // can be returned.
    ColumnConverter(idx int) ValueConverter
}

type Conn

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)
}

type ConnBeginTx 1.8

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)
}

type ConnPrepareContext 1.8

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)
}

type Connector 1.10

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
}

type Driver

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)
}

type DriverContext 1.10

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)
}

type Execer

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)
}

type ExecerContext 1.8

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)
}

type IsolationLevel 1.8

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

type NamedValue 1.8

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
}

type NamedValueChecker 1.9

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
}

type NotNull

NotNull is a type that implements ValueConverter by disallowing nil values but otherwise delegating to another ValueConverter. 

type NotNull struct {
    Converter ValueConverter
}

func (NotNull) ConvertValue 

func (n NotNull) ConvertValue(v any) (Value, error)

type Null

Null is a type that implements ValueConverter by allowing nil values but otherwise delegating to another ValueConverter. 

type Null struct {
    Converter ValueConverter
}

func (Null) ConvertValue 

func (n Null) ConvertValue(v any) (Value, error)

type Pinger 1.8

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
}

type Queryer 1.1

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)
}

type QueryerContext 1.8

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)
}

type Result

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)
}

type Rows

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
}

type RowsAffected

RowsAffected implements Result for an INSERT or UPDATE operation which mutates a number of rows. 

type RowsAffected int64

func (RowsAffected) LastInsertId 

func (RowsAffected) LastInsertId() (int64, error)

func (RowsAffected) RowsAffected 

func (v RowsAffected) RowsAffected() (int64, error)

type RowsColumnTypeDatabaseTypeName 1.8

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
}

type RowsColumnTypeLength 1.8

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)
}

type RowsColumnTypeNullable 1.8

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)
}

type RowsColumnTypePrecisionScale 1.8

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)
}

type RowsColumnTypeScanType 1.8

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
}

type RowsNextResultSet 1.8

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
}

type SessionResetter 1.10

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
}

type Stmt

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)
}

type StmtExecContext 1.8

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)
}

type StmtQueryContext 1.8

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)
}

type Tx

Tx is a transaction. 

type Tx interface {
    Commit() error
    Rollback() error
}

type TxOptions 1.8

TxOptions holds the transaction options.

This type should be considered identical to database/sql.TxOptions. 

type TxOptions struct {
    Isolation IsolationLevel
    ReadOnly  bool
}

type Validator 1.15

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
}

type Value

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

type ValueConverter

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: 

type ValueConverter interface {
    // ConvertValue converts a value to a driver Value.
    ConvertValue(v any) (Value, error)
}

type Valuer

Valuer is the interface providing the Value method.

Errors returned by the Value method are wrapped by the database/sql package. This allows callers to use errors.Is for precise error handling after operations like database/sql.Query, database/sql.Exec, or database/sql.QueryRow.

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)
}
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