Finding and killing long running MySQL queries

Sometimes (Woocommerce?) related queries on a MySQL server can seemingly run forever and eventually lead to the server being clogged up (and few free connections). Something like this can help …. (i.e. kill all MySQL queries which have been running longer than 900 seconds, and aren’t from the ‘root’ user).

Cleaning up a lot of WordPress _transients

WordPress seems to like hiding a load of ‘transient’ (cacheable) stuff in it’s wp_options table. Unfortunately for one site, it seems it didn’t bother to clean up the transient stuff, leaving behind about 750,000 records… which made a WP version upgrade painful, as MySQL locks the wp_option table which causes all other page loads to… Continue reading Cleaning up a lot of WordPress _transients

PostgreSQL unbuffered queries and PHP (cursors)

From using MySQL, I’ve used the ‘unbuffered queries‘ feature a number of times. It’s where you don’t fetch the entire resultset into memory at once – which is necessary if you’re retrieving more data than you have memory available. If’s often also generally gets results/data back to you sooner.

MySQL update/write query analysis (query profiling)

Do you have a slow MySQL update/insert/delete query? Obviously, for ‘SELECT’ queries you can prepend the query with “EXPLAIN ” – however that doesn’t work for the other query types (UPDATE/INSERT/DELETE). So, one solution which may explain why the query is slow is to turn on MySQL’s profiling functionality, like in the following example :