rihad <rihad@xxxxxxx> writes: > If an autovacuum job on a huge table runs for 5-6 hours, do its freed > pages/tuples become available for reuse immediately when they are marked > as free, or only at the end of the multi-hour vacuum operation? They'll be freed in batches, where the size of a batch depends on the autovacuum_work_mem or maintenance_work_mem setting. The basic work cycle is * scan table to find dead tuples, save their TIDs in working memory; continue until end of table or working memory full * scan indexes to find index entries matching those TIDs, remove 'em * go back to table and remove the previously-found tuples * if not end of table, repeat So a larger work-mem setting means fewer passes over the indexes, but a longer time until space is reclaimed. regards, tom lane
