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PHP : Function Reference : MySQL Improved Extension : mysqli_autocommit

mysqli_autocommit

Turns on or off auto-commiting database modifications (PHP 5)
bool mysqli_autocommit ( mysqli link, bool mode )

Example 1470. Object oriented style

<?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();
?>

Example 1471. Procedural style

<?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($link, TRUE);

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);
?>

Code Examples / Notes » mysqli_autocommit

geoffrey thubron

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.


will

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.


glen

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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mysqli_affected_rows
mysqli_autocommit
mysqli_bind_param
mysqli_bind_result
mysqli_change_user
mysqli_character_set_name
mysqli_client_encoding
mysqli_close
mysqli_commit
mysqli_connect_errno
mysqli_connect_error
mysqli_connect
mysqli_data_seek
mysqli_debug
mysqli_disable_reads_from_master
mysqli_disable_rpl_parse
mysqli_dump_debug_info
mysqli_embedded_server_end
mysqli_embedded_server_start
mysqli_enable_reads_from_master
mysqli_enable_rpl_parse
mysqli_errno
mysqli_error
mysqli_escape_string
mysqli_execute
mysqli_fetch_array
mysqli_fetch_assoc
mysqli_fetch_field_direct
mysqli_fetch_field
mysqli_fetch_fields
mysqli_fetch_lengths
mysqli_fetch_object
mysqli_fetch_row
mysqli_fetch
mysqli_field_count
mysqli_field_seek
mysqli_field_tell
mysqli_free_result
mysqli_get_charset
mysqli_get_client_info
mysqli_get_client_version
mysqli_get_host_info
mysqli_get_metadata
mysqli_get_proto_info
mysqli_get_server_info
mysqli_get_server_version
mysqli_get_warnings
mysqli_info
mysqli_init
mysqli_insert_id
mysqli_kill
mysqli_master_query
mysqli_more_results
mysqli_multi_query
mysqli_next_result
mysqli_num_fields
mysqli_num_rows
mysqli_options
mysqli_param_count
mysqli_ping
mysqli_prepare
mysqli_query
mysqli_real_connect
mysqli_real_escape_string
mysqli_real_query
mysqli_report
mysqli_rollback
mysqli_rpl_parse_enabled
mysqli_rpl_probe
mysqli_rpl_query_type
mysqli_select_db
mysqli_send_long_data
mysqli_send_query
mysqli_server_end
mysqli_server_init
mysqli_set_charset
mysqli_set_local_infile_default
mysqli_set_local_infile_handler
mysqli_set_opt
mysqli_slave_query
mysqli_sqlstate
mysqli_ssl_set
mysqli_stat
mysqli_stmt_affected_rows
mysqli_stmt_attr_get
mysqli_stmt_attr_set
mysqli_stmt_bind_param
mysqli_stmt_bind_result
mysqli_stmt_close
mysqli_stmt_data_seek
mysqli_stmt_errno
mysqli_stmt_error
mysqli_stmt_execute
mysqli_stmt_fetch
mysqli_stmt_field_count
mysqli_stmt_free_result
mysqli_stmt_get_warnings
mysqli_stmt_init
mysqli_stmt_insert_id
mysqli_stmt_num_rows
mysqli_stmt_param_count
mysqli_stmt_prepare
mysqli_stmt_reset
mysqli_stmt_result_metadata
mysqli_stmt_send_long_data
mysqli_stmt_sqlstate
mysqli_stmt_store_result
mysqli_store_result
mysqli_thread_id
mysqli_thread_safe
mysqli_use_result
mysqli_warning_count
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