The rows column in an EXPLAIN is read as a measurement — “this query looked at 8,412 rows”. It is the optimiser’s guess, derived from index statistics, and…
MySQL 5.5 made InnoDB the default engine, which is often read as “we are on 5.5, so we have transactions”. Tables created under 5.1 keep MyISAM through an…
Two pages read the same column and only one of them was right. Dumping, rewriting and reloading 52,000 rows without turning every accent into a question mark.
Every option row marked autoload = yes is fetched on every single request, as one query that loads the lot into memory. add_option() takes an argument to opt…
By default mysqldump locks every table it is reading, which on a busy database means writes queue behind the backup for as long as it runs. –single-transaction instead…