mysqli::autocommit

mysqli_autocommit

(PHP 5, PHP 7, PHP 8)

mysqli::autocommit -- mysqli_autocommit — Active ou désactive le mode auto-commit

Description

Style orienté objet

public mysqli::autocommit(bool $enable): bool

Style procédural

mysqli_autocommit(mysqli $mysql, bool $enable): bool

Active ou désactive le mode auto-commit pour les requêtes sur la connexion.

Pour vérifier l'état de l'auto-commit, utilisez la commande SQL SELECT @@autocommit.

Liste de paramètres

mysql: Seulement en style procédural : Un objet mysqli retourné par la fonction mysqli_connect() ou mysqli_init().
enable: Si l'on doit activer ou non l'auto-commit.

Valeurs de retour

Cette fonction retourne true en cas de succès ou false si une erreur survient.

Erreurs / Exceptions

Si le rapport d'erreurs mysqli est activé (MYSQLI_REPORT_ERROR) et que l'opération demandée échoue, un avertissement est généré. Si, en plus, le mode est défini sur MYSQLI_REPORT_STRICT, une mysqli_sql_exception est lancée à la place.

Exemples

Exemple #1 Exemple avec mysqli::autocommit()

Style orienté objet

<?php

/* Demande à mysqli de lancer une exception si une erreur survient */
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);

$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

/* Le moteur de table supporte les transactions */
$mysqli->query("CREATE TABLE IF NOT EXISTS language (
    Code text NOT NULL,
    Speakers int(11) NOT NULL
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;");

/* Désactive l'autocommit */
$mysqli->autocommit(false);

$result = $mysqli->query("SELECT @@autocommit");
$row = $result->fetch_row();
printf("L'Autocommit vaut %s\n", $row[0]);

try {
    /* Prépare une requête d'insertion */
    $stmt = $mysqli->prepare('INSERT INTO language(Code, Speakers) VALUES (?,?)');
    $stmt->bind_param('ss', $language_code, $native_speakers);

    /* Insère plusieurs valeurs */
    $language_code = 'DE';
    $native_speakers = 50_123_456;
    $stmt->execute();
    $language_code = 'FR';
    $native_speakers = 40_546_321;
    $stmt->execute();

    /* Commit les données dans la base de données. Ceci n'active pas l'autocommit */
    $mysqli->commit();
    print "Validation de 2 lignes dans la base de données\n";

    $result = $mysqli->query("SELECT @@autocommit");
    $row = $result->fetch_row();
    printf("L'autocommit vaut %s\n", $row[0]);

    /* Tente d'insérer plusieurs valeurs */
    $language_code = 'PL';
    $native_speakers = 30_555_444;
    $stmt->execute();
    $language_code = 'DK';
    $native_speakers = 5_222_444;
    $stmt->execute();

    /* Le fait de définir autocommit=true va déclencher le commit */
    $mysqli->autocommit(true);

    print "Validation de 2 lignes dans la base de données\n";
} catch (mysqli_sql_exception $exception) {
    $mysqli->rollback();

    throw $exception;
}

Style procédural

<?php

/* Demande à mysqli de lancer une exception si une erreur survient */
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);

$mysqli = mysqli_connect("localhost", "my_user", "my_password", "world");

/* Le moteur de table supporte les transactions */
mysqli_query($mysqli, "CREATE TABLE IF NOT EXISTS language (
    Code text NOT NULL,
    Speakers int(11) NOT NULL
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;");

/* Désactive l'autocommit */
mysqli_autocommit($mysqli, false);

$result = mysqli_query($mysqli, "SELECT @@autocommit");
$row = mysqli_fetch_row($result);
printf("L'Autocommit vaut %s\n", $row[0]);

try {
    /* Prépare une requête d'insertion */
    $stmt = mysqli_prepare($mysqli, 'INSERT INTO language(Code, Speakers) VALUES (?,?)');
    mysqli_stmt_bind_param($stmt, 'ss', $language_code, $native_speakers);

    /* Insère plusieurs valeurs */
    $language_code = 'DE';
    $native_speakers = 50_123_456;
    mysqli_stmt_execute($stmt);
    $language_code = 'FR';
    $native_speakers = 40_546_321;
    mysqli_stmt_execute($stmt);

    /* Commit les données dans la base de données. Ceci n'active pas l'autocommit */
    mysqli_commit($mysqli);
    print "Validation de 2 lignes dans la base de données\n";

    $result = mysqli_query($mysqli, "SELECT @@autocommit");
    $row = mysqli_fetch_row($result);
    printf("L'autocommit vaut %s\n", $row[0]);

    /* Tente d'insérer plusieurs valeurs */
    $language_code = 'PL';
    $native_speakers = 30_555_444;
    mysqli_stmt_execute($stmt);
    $language_code = 'DK';
    $native_speakers = 5_222_444;
    mysqli_stmt_execute($stmt);

    /* Le fait de définir autocommit=true va déclencher le commit */
    mysqli_autocommit($mysqli, true);

    print "Validation de 2 lignes dans la base de données\n";
} catch (mysqli_sql_exception $exception) {
    mysqli_rollback($mysqli);

    throw $exception;
}

Les exemples ci-dessus vont afficher :

L'autocommit vaut 0
Validation de 2 lignes dans la base de données
L'autocommit vaut 0
Validation de 2 lignes dans la base de données
L'autocommit vaut 0
Validation de 2 lignes dans la base de données
L'autocommit vaut 0
Validation de 2 lignes dans la base de données

Notes

Note:
Cette fonction ne fonctionne pas avec les types de tables non transactionnelles, comme MyISAM ou ISAM.

Voir aussi

mysqli_begin_transaction() - Démarre une transaction
mysqli_commit() - Valide la transaction courante
mysqli_rollback() - Annule la transaction courante

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User Contributed Notes 3 notes

down

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.

down

Geoffrey Thubron ¶

17 years ago

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.

down

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.

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