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207 lines (174 loc) · 5.22 KB
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package pgx
import (
"errors"
"fmt"
)
// Transaction isolation levels
const (
Serializable = "serializable"
RepeatableRead = "repeatable read"
ReadCommitted = "read committed"
ReadUncommitted = "read uncommitted"
)
const (
TxStatusInProgress = 0
TxStatusCommitFailure = -1
TxStatusRollbackFailure = -2
TxStatusCommitSuccess = 1
TxStatusRollbackSuccess = 2
)
var ErrTxClosed = errors.New("tx is closed")
// ErrTxCommitRollback occurs when an error has occurred in a transaction and
// Commit() is called. PostgreSQL accepts COMMIT on aborted transactions, but
// it is treated as ROLLBACK.
var ErrTxCommitRollback = errors.New("commit unexpectedly resulted in rollback")
// Begin starts a transaction with the default isolation level for the current
// connection. To use a specific isolation level see BeginIso.
func (c *Conn) Begin() (*Tx, error) {
return c.begin("")
}
// BeginIso starts a transaction with isoLevel as the transaction isolation
// level.
//
// Valid isolation levels (and their constants) are:
// serializable (pgx.Serializable)
// repeatable read (pgx.RepeatableRead)
// read committed (pgx.ReadCommitted)
// read uncommitted (pgx.ReadUncommitted)
func (c *Conn) BeginIso(isoLevel string) (*Tx, error) {
return c.begin(isoLevel)
}
func (c *Conn) begin(isoLevel string) (*Tx, error) {
var beginSQL string
if isoLevel == "" {
beginSQL = "begin"
} else {
beginSQL = fmt.Sprintf("begin isolation level %s", isoLevel)
}
_, err := c.Exec(beginSQL)
if err != nil {
return nil, err
}
return &Tx{conn: c}, nil
}
// Tx represents a database transaction.
//
// All Tx methods return ErrTxClosed if Commit or Rollback has already been
// called on the Tx.
type Tx struct {
conn *Conn
afterClose func(*Tx)
err error
status int8
}
// Commit commits the transaction
func (tx *Tx) Commit() error {
if tx.status != TxStatusInProgress {
return ErrTxClosed
}
commandTag, err := tx.conn.Exec("commit")
if err == nil && commandTag == "COMMIT" {
tx.status = TxStatusCommitSuccess
} else if err == nil && commandTag == "ROLLBACK" {
tx.status = TxStatusCommitFailure
tx.err = ErrTxCommitRollback
} else {
tx.status = TxStatusCommitFailure
tx.err = err
}
if tx.afterClose != nil {
tx.afterClose(tx)
}
return tx.err
}
// Rollback rolls back the transaction. Rollback will return ErrTxClosed if the
// Tx is already closed, but is otherwise safe to call multiple times. Hence, a
// defer tx.Rollback() is safe even if tx.Commit() will be called first in a
// non-error condition.
func (tx *Tx) Rollback() error {
if tx.status != TxStatusInProgress {
return ErrTxClosed
}
_, tx.err = tx.conn.Exec("rollback")
if tx.err == nil {
tx.status = TxStatusRollbackSuccess
} else {
tx.status = TxStatusRollbackFailure
}
if tx.afterClose != nil {
tx.afterClose(tx)
}
return tx.err
}
// Exec delegates to the underlying *Conn
func (tx *Tx) Exec(sql string, arguments ...interface{}) (commandTag CommandTag, err error) {
if tx.status != TxStatusInProgress {
return CommandTag(""), ErrTxClosed
}
return tx.conn.Exec(sql, arguments...)
}
// Prepare delegates to the underlying *Conn
func (tx *Tx) Prepare(name, sql string) (*PreparedStatement, error) {
return tx.PrepareEx(name, sql, nil)
}
// PrepareEx delegates to the underlying *Conn
func (tx *Tx) PrepareEx(name, sql string, opts *PrepareExOptions) (*PreparedStatement, error) {
if tx.status != TxStatusInProgress {
return nil, ErrTxClosed
}
return tx.conn.PrepareEx(name, sql, opts)
}
// Query delegates to the underlying *Conn
func (tx *Tx) Query(sql string, args ...interface{}) (*Rows, error) {
if tx.status != TxStatusInProgress {
// Because checking for errors can be deferred to the *Rows, build one with the error
err := ErrTxClosed
return &Rows{closed: true, err: err}, err
}
return tx.conn.Query(sql, args...)
}
// QueryRow delegates to the underlying *Conn
func (tx *Tx) QueryRow(sql string, args ...interface{}) *Row {
rows, _ := tx.Query(sql, args...)
return (*Row)(rows)
}
// Deprecated. Use CopyFrom instead. CopyTo delegates to the underlying *Conn
func (tx *Tx) CopyTo(tableName string, columnNames []string, rowSrc CopyToSource) (int, error) {
if tx.status != TxStatusInProgress {
return 0, ErrTxClosed
}
return tx.conn.CopyTo(tableName, columnNames, rowSrc)
}
// CopyFrom delegates to the underlying *Conn
func (tx *Tx) CopyFrom(tableName Identifier, columnNames []string, rowSrc CopyFromSource) (int, error) {
if tx.status != TxStatusInProgress {
return 0, ErrTxClosed
}
return tx.conn.CopyFrom(tableName, columnNames, rowSrc)
}
// Conn returns the *Conn this transaction is using.
func (tx *Tx) Conn() *Conn {
return tx.conn
}
// Status returns the status of the transaction from the set of
// pgx.TxStatus* constants.
func (tx *Tx) Status() int8 {
return tx.status
}
// Err returns the final error state, if any, of calling Commit or Rollback.
func (tx *Tx) Err() error {
return tx.err
}
// AfterClose adds f to a LILO queue of functions that will be called when
// the transaction is closed (either Commit or Rollback).
func (tx *Tx) AfterClose(f func(*Tx)) {
if tx.afterClose == nil {
tx.afterClose = f
} else {
prevFn := tx.afterClose
tx.afterClose = func(tx *Tx) {
f(tx)
prevFn(tx)
}
}
}