mysqli::autocommit

mysqli_autocommit

(PHP 5)

mysqli::autocommit -- mysqli_autocommitAtiva ou desativa o salvar automaticamente as modificações no banco de dados

Descrição

Estilo orientado a objeto(metodo)

bool mysqli::autocommit ( bool $mode )

Estilo de procedimento:

bool mysqli_autocommit ( mysqli $link , bool $mode )

mysqli_autocommit() é usado para ativar ou desativar o modo de salvar automaticamente as consultas para a conexão com o banco dedados representado por link. object.

Nota:

Para determinar o estado do salvar automaticamente use o comando SQL 'SELECT @@autocommit'.

Valor Retornado

Retorna TRUE em caso de sucesso ou FALSE em caso de falha.

Notas

Nota:

mysqli_autocommit() Não funciona com tabelas de tipos não baseadas em transações (como MyISAM ou ISAM).

Exemplos

Exemplo #1 Estilo orientado a objeto

<?php
$mysqli 
= new mysqli("localhost""my_user""my_password""world");

if (
mysqli_connect_errno()) {
    
printf("Connect failed: %s\n"mysqli_connect_error());
    exit();
}

/* turn autocommit on */
$mysqli->autocommit(TRUE);

if (
$result $mysqli->query("SELECT @@autocommit")) {
    
$row $result->fetch_row();
    
printf("Autocommit is %s\n"$row[0]);
    
$result->free();
}

/* close connection */
$mysqli->close();
?>

Exemplo #2 Estilo de procedimento

<?php
$link 
mysqli_connect("localhost""my_user""my_password""world");

if (!
$link) {
    
printf("Can't connect to localhost. Error: %s\n"mysqli_connect_error());
    exit();
}

/* turn autocommit on */
mysqli_autocommit($linkTRUE);

if (
$result mysqli_query($link"SELECT @@autocommit")) {
    
$row mysqli_fetch_row($result);
    
printf("Autocommit is %s\n"$row[0]);
    
mysqli_free_result($result);
}

/* close connection */
mysqli_close($link);
?>

O exemplo acima irá imprimir:

Autocommit is 1

Veja Também

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User Contributed Notes 5 notes

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8
jcwebb at dicoe dot com
6 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.
up
3
Geoffrey Thubron
7 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.
up
2
Glen
7 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.
up
1
rusxakep
7 days ago
Glen,

In persistent connection's, you should run autocommit (true) in shutdown function, otherwise, you got lock's in "post" (not transactional) query's.

No commit and not rollback function's don't back autocommit value.

<?php
   
/**
     * @return bool
     */
   
public function begin_transaction() {
        if (!
$this->link->autocommit(false)) return FALSE;
       
$this->t_in_progress = true;
       
register_shutdown_function([$this, "__shutdown_check"]);
       
$this->link->begin_transaction();
        return
TRUE;
    }

   
/**
     *
     */
   
public function __shutdown_check() {
        if (
$this->t_in_progress) {
           
$this->rollback();
        }
        if (!
$this->link->autocommit(true)) return FALSE;
    }

   
/**
     * @return bool
     */
   
public function commit() {
        if (!
$this->link->commit()) return FALSE;
       
$this->t_in_progress = false;
        return
TRUE;
    }

   
/**
     * @return bool
     */
   
public function rollback() {
        if (!
$this->link->rollback()) return FALSE;
       
$this->t_in_progress = false;
        return
TRUE;
    }
?>
up
0
will at phpfever dot com
8 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.
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