It's worth noting that you can perform transactions without disabling autocommit just using standard sql. "START TRANSACTION;" will start a transaction. "COMMIT;" will commit the results and "ROLLBACK;" will revert to the pre-transaction state.
CREATE TABLE and CREATE DATABASE (and probably others) are always commited immediately and your transaction appears to terminate. Thus any commands before and after will be commited, even if a subsequent rollback is attempted.
If you are in the middle of a transaction and you call mysqli_close() it appears that you get the funcitonality of an implicit rollback.
I can't reproduce the "code bug causes lock" problem outlined below (I always get a successful rollback and the script will run umtine times successfully). Therefore, I would suggest that the problem is fixed in php-5.2.2.
mysqli::autocommit
mysqli_autocommit
(PHP 5, PHP 7, PHP 8)
mysqli::autocommit -- mysqli_autocommit — Activa o desactiva las modificaciones de la base de datos autoconsignadas
Descripción
Estilo orientado a objetos
Estilo por procedimientos
Activa o desactiva el modo 'auto-commit' en consultas para la conexión a la base de datos.
Para determinar el estado actual de la autoconsigna se ha de utilzar el comando SQL
SELECT @@autocommit.
Parámetros
-
link -
Sólo estilo por procediminetos: Un identificador de enlace devuelto por mysqli_connect() o mysqli_init()
-
mode -
Si activar o no el modo 'auto-commit'.
Valores devueltos
Devuelve true en caso de éxito o false en caso de error.
Notas
Nota:
Esta función no puede aplicarse a tipos de tablas no transaccionales (como MyISAM o ISAM).
Ejemplos
Ejemplo #1 Ejemplo de mysqli::autocommit()
Estilo orientado a objetos
<?php
$mysqli = new mysqli("localhost", "mi_usuario", "mi_contraseña", "world");
if (mysqli_connect_errno()) {
printf("Fallo la conexión: %s\n", mysqli_connect_error());
exit();
}
/* activar la autoconsigna */
$mysqli->autocommit(TRUE);
if ($resultado = $mysqli->query("SELECT @@autocommit")) {
$fila = $resultado->fetch_row();
printf("El estado de la autoconsigna es %s\n", $fila[0]);
$resultado->free();
}
/* Cerrar conexión */
$mysqli->close();
?>Estilo por procedimientos
<?php
$enlace = mysqli_connect("localhost", "mi_usuario", "mi_contraseña", "world");
if (!$enlace) {
printf("Imposible conectar a localhost. Error: %s\n", mysqli_connect_error());
exit();
}
/* activar la autoconsigna */
mysqli_autocommit($enlace, TRUE);
if ($resultado = mysqli_query($enlace, "SELECT @@autocommit")) {
$fila = mysqli_fetch_row($resultado);
printf("El estado de la autoconsigna es %s\n", $fila[0]);
mysqli_free_result($resultado);
}
/* close connection */
mysqli_close($enlace);
?>El resultado de los ejemplos sería:
El estado de la autoconsigna es 1
Ver también
- mysqli_begin_transaction() - Inicia una transacción
- mysqli_commit() - Consigna la transacción actual
- mysqli_rollback() - Revierte la transacción actual
add a note
User Contributed Notes 4 notes
Geoffrey Thubron ¶
17 years ago
jcwebb at dicoe dot com ¶
17 years ago
Just to be clear, autocommit not only turns on/off transactions, but will also 'commit' any waiting queries.
<?php
mysqli_autocommit($link, FALSE); // turn OFF auto
-some query 1;
-some query 2;
mysqli_commit($link); // process ALL queries so far
-some query 3;
-some query 4;
mysqli_autocommit($link, TRUE); // turn ON auto
?>
All 4 will be processed.
Glen ¶
17 years ago
I've found that if PHP exits due to a code bug during a transaction, an InnoDB table can remain locked until Apache is restarted.
The simple test is to start a transaction by setting $mysqli_obj->autocommit(false) and executing an insert statement. Before getting to a $mysqli_obj->commit statement - have a runtime code bug bomb PHP. You check the database, no insert happened (you assume a rollback occurred) .. and you go fix the bug, and try again... but this time the script takes about 50 seconds to timeout - the insert statement returning with a “1205 - Lock wait timeout exceeded; try restarting transaction”. No rollback occurred. And this error will not go away until you restart Apache - for whatever reason, the resources are not released until the process is killed.
I found that an ‘exit’, instead of a PHP code bug, will not cause a problem. So there is an auto-rollback mechanism in place - it just fails miserably when PHP dies unexpectantly. Having to restarting apache is a pretty drastic measure to overcome a code bug.
To avoid this problem, I use “register_shutdown_function()” when I start a transaction, and set a flag to indicate a transaction is in process (because there is no unregister_shutdown_function()). See below. So the __shutdown_check() routine (I beleive it needs to be public) is called when the script bombs - which is able to invoke the rollback().
these are just the relevant bits to give u an idea...
<?php
public function begin_transaction() {
$ret = $this->mysqli_obj->autocommit(false);
$this->transaction_in_progress = true;
register_shutdown_function(array($this, "__shutdown_check"));
}
public function __shutdown_check() {
if ($this->transaction_in_progress) {
$this->rollback();
}
}
public function commit() {
$ret = $this->mysqli_obj->commit();
$this->transaction_in_progress = false;
}
public function rollback() {
$ret = $this->mysqli_obj->rollback();
$this->transaction_in_progress = false;
}
?>
True for PHP 5.1.6 + MySQL 5.0.24a.
will at phpfever dot com ¶
18 years ago
If you are using the mysql command line tool, here are some helpful hints for the autocommit feature:
1. To view the current autocommit setting, you can use this query: select @@autocommit; It will return the current setting as 1 or 0 (on or off)
2. You can manage the default autocommit feature in you my.cnf or my.ini by adding the following line: init_connect='set autocommit=0'. I'm pretty sure this isn't in the documentation, but it does work.
Here are the current engines, as of MySQL 5.1dev that support transactions:
InnoDB
BerkeleyDB
Falcon
Falcon is very new, so beware using it on production systems.
