An expression in a WHERE clause makes an index unusable, and a generated column moves the expression into something indexable. The automatic substitution is the good part —…
Seconds_Behind_Source is derived from the timestamp of the event being applied, so an idle source reports zero lag on a replica that is minutes behind. The failure that…
Checking whether a key exists and then inserting it is two statements and a race, and the race is precisely the concurrent-retry case the key exists to handle.…
8.0.22 deprecated the old replication vocabulary in favour of source and replica, and every script and runbook contains the old words. The column renames are what break monitoring…
EXPLAIN shows the plan and the optimiser’s estimates, and the estimates are frequently wrong — a query planned for 40 rows that reads 400,000 looks entirely healthy. The…
Each condition in a meta_query becomes another self-join against a table that is usually the largest in the database. Modelling a filterable attribute as a taxonomy rather than…