How to calculate storage usage by the cache?

Hello Manos,

I’m going to reply in English. If you need any clarification, please let me know.

Metadata caching is done via the Transients API of WordPress. The temporary data (metadata cache in this case) is stored in the options table of each blog.

The name of each transient is amt_MD5SUM. WordPress prefixes each name with _transient_, so each transient’s name as it appears in the database table is _transient_amt_MD5SUM.

The following query returns two numbers: 1) the total number of stored Add-Meta-Tags transients and 2) the total used space by those transients:

SELECT COUNT(*), SUM(LENGTH(option_value)) FROM wp_options WHERE option_name LIKE '_transient_amt_%';

Of course, the table name needs to be replaced with the actual table name for the specific blog.

I will investigate the use of the SUM(LENGTH(option_value)) calculation in order to provide an indication in the plugin settings page about the used space by the AMT transients.

I will now mark this topic as resolved. If you need more help with this, please feel free to ask.

Kind Regards,
George

I’ve added a note in my issue tracker to add this information about the used space in the amt command of wp-cli.

Thanks for your feedback.

George

BTW, is the database used as the storage for transients in your environment or you use a more advanced configuration?

Hey Manos,

If you are storing the cache on the WP database, here is an improved SQL query to calculate the storage space that is used:

SELECT COUNT(*), SUM(LENGTH(option_value)) \
  FROM wp_options \
  WHERE \
    option_name LIKE '_transient_amt_%' OR \
    option_name LIKE '_transient_timeout_amt_%';

Hope this helps.

George