Nikita wrote: > 1. pg_total_relation_size return predictable approximately correct table size > (apart from some preallocation) without subsequent VACUUM/ANALYZE/anything > call as long as I don't DELETE/UPDATE rows; > > 2. DROP/TRUNCATE table reclaim disc space without subsequent VACUUM; > > These assumptions are correct? Is it fixed in doc if so?
Sort of, if you consider the source as documentation. Ad pg_total_relation_size: See the function definition in backend/utils/adt/dbsize.c and the functions that it calls, especially "calculate_relation_size": PostgreSQL uses the stat(2) system call to determine the actual size of the files on disk. Ad TRUNCATE (from backend/commands/tablecmds.c): /* * Need the full transaction-safe pushups. * * Create a new empty storage file for the relation, and assign it * as the relfilenode value. The old storage file is scheduled for * deletion at commit. */ Yours, Laurenz Albe
