caching – Page 12 – Türker Yıldırım

WooCommerce sessions are not PHP sessions

NoteSeptember 7, 20161 min read

WooCommerce maintains its own session handler backed by a database table and a cookie, entirely separate from $_SESSION. Code that starts a PHP session to store something cart-related…

Object cache groups, and which ones are global

NoteAugust 16, 20161 min read

On multisite the object cache prefixes keys with the current blog id, so the same key on two sites does not collide. Some groups must not be prefixed…

One large autoloaded option is on every single request

NoteJune 9, 20161 min read

The failure mode is not a slow query. It is one option holding a megabyte of serialised data, fetched and unserialised on every request, quietly adding both to…

The N+1 queries you did not write

Deep diveJune 3, 20168 min read

1,400 queries on a page showing 40 rows. Eager loading, the difference between with() and load(), and the accessor that no eager load can fix.

Moving catalogue search off MySQL and onto Elasticsearch

Deep diveMay 18, 201615 min read

LIKE cannot use an index and everyone knows it. The mapping, the analyzers that decide what matching means, the indexing pipeline, and the drift it introduces.

wp_cache_add refuses to overwrite; wp_cache_set does not

NoteApril 7, 20161 min read

The two look interchangeable and differ on whether the key already exists: set() overwrites unconditionally, add() fails and returns false. That failure is the useful part. With a…

Finding the 200 milliseconds nobody could account for

Deep diveMarch 31, 20168 min read

The page took 340ms and the parts added up to 140. Measuring from the first byte nginx sees rather than from the framework boot, and what was hiding…

Reading EXPLAIN until a slow catalogue query gets fast

Deep diveOctober 30, 20158 min read

4.2 seconds on 60,000 rows. Following EXPLAIN from a full table scan to a covering index, and why the composite index that existed was never used.

Filtering a WooCommerce catalogue without the meta tables

Deep diveOctober 6, 201516 min read

Five filters over 30,000 variations, and a request that never returns. Replacing EAV meta joins with a denormalised index table kept in sync by product hooks.

SETEX is atomic where SET plus EXPIRE is not

NoteJuly 29, 20152 min read

Writing a cache entry and then setting its TTL is two commands, and the process can die between them. The result is a key with no expiry that…