mysql – Page 34 – Türker Yıldırım

no_found_rows removes a COUNT query you are not using

NoteDecember 16, 20151 min read

Every WP_Query runs a second query to count the total number of matching rows, so that pagination can be rendered. If the query is powering a sidebar widget…

A first serious attempt at Docker for local development

Deep diveNovember 27, 201515 min read

Two days lost to PHP extension mismatches. A container per service, what the shared-folder performance problem costs on a VM, and whether it was worth it.

Convert a MySQL database to utf8mb4

SnippetNovember 17, 20151 min read

The slow query log costs less than you think to leave on

NoteNovember 17, 20151 min read

The slow query log is usually described as a debugging tool to switch on when there is a problem, which means it is off at exactly the moment…

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.

Reset a MySQL root password

SnippetOctober 7, 20151 min read

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.

SQL_CALC_FOUND_ROWS is usually slower than a second COUNT

NoteSeptember 25, 20151 min read

SQL_CALC_FOUND_ROWS promises the total row count for free alongside a LIMITed page, in one query. The catch is that it forces MySQL to evaluate every matching row rather…

A covering index answers the query without touching rows

NoteSeptember 24, 20151 min read

An index lookup normally finds a primary key and then goes to the table to fetch the columns you asked for — a second read per row. If…

WP_Query fields => ids when you only need the IDs

NoteSeptember 8, 20151 min read

A normal WP_Query hydrates every result into a WP_Post object and primes the meta and term caches for all of them. When the only thing you want is…