WordCamp 2019 - Intro to WP Transients API

talk about caching basically
very specific type

transient - bit of data cached for indeterminate amount of time

two primary uses:

• time consuming queries - meta queries, cache the results in transient
• remote data fetched via the HTTP API - from external site, can set lifecycle

How do they work?

• give a name
• check to see if exists
• use it if there
• get it if not and save it for next time

Transient storage is handled by WP

• WP first checks for memcache redis apc etc
• falls back to wp options table, still faster though

Transient functions are just set/get/delete - set updates anything that exists
nofoundrows = true (turn off for not worrying about pagination)

Ugly query:

Transients:

WP has time constants like HOURINSECONDS so you can multiply that out

Managing changed data:

• have a hook that fires after update
• make sure it isn't a revision, other subtle gotchas to look out for
• can set transient to never die
• if you can regenerate the transient after deletion, you should

Plugins

• Pippin's Transient Manager (Williamson) - see all transients for your site
• Delete Expired Transients - what it says, because they are not always deleted
• Query Monitor - can show you which transients were changed in this page load

WordPress doesn't delete expired data, you always have to refresh
How to do transient deletion with wildcards?
$wpdb->query( "DELETE FROM $wpdb->options WHERE option_name LIKE ('transientgalleries_%')" );
unless in memcached or redis, then you have to use their way to interact with it