DML drivers

Newer Version Available

This documentation is for Moodle 4.4.
You may also want to read the documentation for the upcoming version of Moodle.

A number of native drivers are included with Moodle, including those with support for:

• MySQLi
• MariaDB
• PostgreSQL
• Oracle
• Microsoft SQL Server

These drivers are supported using DML Database Driver layer, which has a number of discreet benefits:

• more optimised and probably faster
• consume less memory
• better possibility to improve logging, debugging, profiling, etc.
• less code, easier to fix and maintain
• and more

Query logging

The native DML drivers support logging of database queries to database table, which can be enabled in config.php:

config.php

$CFG->dboptions = [
    'dbpersist' => 0,
    //'logall'   => true,
    'logslow'  => 5,
    'logerrors'  => true,
];

• logall - log all queries - suitable only for developers, causes high server loads
• logslow - log queries that take longer than specified number of seconds (float values are accepted)
• logerrors - log all error queries

See also

• DML functions: Where all the functions used to handle DB data (DML) are defined.
• DML exceptions: New DML code is throwing exceptions instead of returning false if anything goes wrong