On Tue, Apr 30, 2024 at 3:34 PM Anthonin Bonnefoy <anthonin.bonne...@datadoghq.com> wrote: > > I've done some additional tests to validate the reported numbers. Using > pg_statio, it's possible to get the minimum number of block hits (Full script > attached). > > -- Save block hits before vacuum > SELECT pg_stat_force_next_flush(); > SELECT heap_blks_hit, idx_blks_hit FROM pg_statio_all_tables where > relname='vestat' \gset > vacuum (verbose, index_cleanup on) vestat; > -- Check the difference > SELECT pg_stat_force_next_flush(); > SELECT heap_blks_hit - :heap_blks_hit as delta_heap_hit, > idx_blks_hit - :idx_blks_hit as delta_idx_hit, > heap_blks_hit - :heap_blks_hit + idx_blks_hit - :idx_blks_hit as sum > FROM pg_statio_all_tables where relname='vestat'; > > Output: > ... > buffer usage: 14676 hits, 0 misses, 667 dirtied > buffer usage (new): 16081 hits, 0 misses, 667 dirtied > ... > -[ RECORD 1 ]--+------ > delta_heap_hit | 9747 > delta_idx_hit | 6325 > sum | 16072 > > From pg_statio, we had 16072 blocks for the relation + indexes. > Pre-patch, we are under reporting with 14676. > Post-patch, we have 16081. The 9 additional block hits come from vacuum > accessing catalog tables like pg_class or pg_class_oid_index. >
Thank you for further testing! I've pushed the patch. Regards, -- Masahiko Sawada Amazon Web Services: https://aws.amazon.com
