A nightly dump that has exited zero for two years proves the dump command works, which is a different claim from the data being recoverable. Asserting on a…
The default dump contains tables and data and none of the stored programs, so a restore produces a database that looks complete and behaves differently. –single-transaction gives a…
The aggregate boundary is not a modelling preference — it is the answer to which invariants have to hold at every instant, and everything else can be eventually…
Window functions are computed after WHERE and GROUP BY, so a predicate on the result has nowhere to go in the same query block. Putting the restriction inside…
The slow log ranks by individual duration, so a query taking two seconds once appears above one taking 40 milliseconds two hundred thousand times — and the second…
Indexing an expression is not possible directly, so a query filtering on YEAR(placed_at) or on a JSON path scans the table regardless of what indexes exist. The optimiser…
3.6 added lookup tables, which is WooCommerce admitting postmeta does not scale. What they contain, what they do not, and the regeneration nobody schedules.