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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.
//
// Code simply using databases should use package sql.
//
// Drivers only need to be aware of a subset of Go's types. The db package
// will convert all types into one of the following:
//
// int64
// float64
// bool
// nil
// []byte
// string [*] everywhere except from Rows.Next.
//
package driver
import "errors"
// Driver is the interface that must be implemented by a database
// driver.
type Driver interface {
// Open returns a new or cached connection to the database.
// The name is a string in a driver-specific format.
//
// The returned connection is only used by one goroutine at a
// time.
Open(name string) (Conn, error)
}
// Execer is an optional interface that may be implemented by a Driver
// or a Conn.
//
// If a Driver does not implement Execer, the sql package's DB.Exec
// method first obtains a free connection from its free pool or from
// the driver's Open method. Execer should only be implemented by
// drivers that can provide a more efficient implementation.
//
// If a Conn does not implement Execer, the db package's DB.Exec will
// first prepare a query, execute the statement, and then close the
// statement.
//
// All arguments are of a subset type as defined in the package docs.
type Execer interface {
Exec(query string, args []interface{}) (Result, 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. The driver may cache or
// close its underlying connection to its database.
Close() error
// Begin starts and returns a new transaction.
Begin() (Tx, error)
}
// 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.
Close() error
// NumInput returns the number of placeholder parameters.
NumInput() int
// Exec executes a query that doesn't return rows, such
// as an INSERT or UPDATE. The args are all of a subset
// type as defined above.
Exec(args []interface{}) (Result, error)
// Exec executes a query that may return rows, such as a
// SELECT. The args of all of a subset type as defined above.
Query(args []interface{}) (Rows, error)
}
// ColumnConverter may be optionally implemented by Stmt if the
// the statement is aware of its own columns' types and can
// convert from any type to a driver subset type.
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.
//
// The dest slice may be populated with only with values
// of subset types defined above, but excluding string.
// All string values must be converted to []byte.
Next(dest []interface{}) error
}
// 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("no LastInsertId available")
}
func (v RowsAffected) RowsAffected() (int64, error) {
return int64(v), nil
}
// DDLSuccess is a pre-defined Result for drivers to return when a DDL
// command succeeds.
var DDLSuccess ddlSuccess
type ddlSuccess struct{}
var _ Result = ddlSuccess{}
func (ddlSuccess) LastInsertId() (int64, error) {
return 0, errors.New("no LastInsertId available after DDL statement")
}
func (ddlSuccess) RowsAffected() (int64, error) {
return 0, errors.New("no RowsAffected available after DDL statement")
}
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