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A pretty darn quick cache. Uses asynchronous connections & prefetching to speed up cache calls & eliminate deadlocks & metadata locks on the cache tables.


MySQL 5.5+, PHP 5.3+, and the mysqlnd driver.

Features & Benefits

  • Eliminates deadlocks & metadata locks for all cache tables.
  • Faster page load times for logged in and anonymous users due to cache prefetching.
  • Outputs query information to the devel query log. Will output prefetch info as well.
  • Better handing of the minimum cache lifetime; does smarter garbage collection of the cache bins. Purges caches based on individual records' timestamps instead of just using the expire column, the created column is used as well.
  • Changes the collation of cache tables to utf8_bin. Using the utf8_bin collation is faster and more accurate when matching cache ids since no unicode normalization is done to cache query conditions. D8 backport of (#2352207: Database cache backend does not treat cid as case sensitive).
  • Changes the semaphore table to use the MEMORY engine if using MySQL 5.5 or lower. This will speed up writes to the lock table for older versions of MySQL.
  • Writes to the watchdog table from the dblog module are done using an async query.
  • Session initialization is done with 1 query instead of 2. Session writes use async queries.
  • Configurable, per bin deflate compression of the data blob resulting in smaller cache tables in the database and faster network transfers if MySQL is on a different box.


The quick and easy way to set this up is to install the module and go to the status report page admin/reports/status. Works with MySQL only at this point.

Below is what you'll typically need to add to your settings.php file.

$databases['default']['default']['init_commands']['isolation'] = "SET SESSION tx_isolation='READ-COMMITTED'";
$databases['default']['default']['init_commands']['lock_wait_timeout'] = "SET SESSION innodb_lock_wait_timeout = 20";
$databases['default']['default']['init_commands']['wait_timeout'] = "SET SESSION wait_timeout = 600";
$conf['cache_backends'][] = 'sites/all/modules/apdqc/';
$conf['cache_default_class'] = 'APDQCache';
$conf['lock_inc'] = 'sites/all/modules/apdqc/';
$conf['session_inc'] = 'sites/all/modules/apdqc/';

Known Issues

The current version of Parallels Plesk does not support php-mysqlnd. It should be fixed in the next release of that software.

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