On Thu, Aug 22, 2019 at 02:44:15PM +0200, Marco Colli wrote: > SELECT COUNT(*) FROM "subscriptions" WHERE "subscriptions"."project_id" = 123; > SELECT COUNT(*) FROM "subscriptions" WHERE "subscriptions"."project_id" = 123 AND "subscriptions"."trashed_at" IS NULL; > -> Bitmap Heap Scan on subscriptions (cost=199573.94..2055635.23 rows=4996823 width=0) (actual time=1666.409..16855.610 rows=4994254 loops=1) > Recheck Cond: (project_id = 123) > Rows Removed by Index Recheck: 23746378 > Heap Blocks: exact=131205 lossy=1480411 > -> Bitmap Index Scan on index_subscriptions_on_project_id_and_trashed_at (cost=0.00..198324.74 rows=4996823 width=0) (actual time=1582.717..1582.717 rows=4994877 loops=1) > -> Bitmap Heap Scan on subscriptions (cost=187953.70..2036810.19 rows=4428599 width=0) (actual time=1644.966..17078.378 rows=4994130 loops=1) > Recheck Cond: ((project_id = 123) AND (trashed_at IS NULL)) > Rows Removed by Index Recheck: 23746273 > Heap Blocks: exact=131144 lossy=1480409 > -> Bitmap Index Scan on index_subscriptions_on_project_id_and_trashed_at (cost=0.00..186846.55 rows=4428599 width=0) (actual time=1566.163..1566.163 rows=4994749 loops=1) You can see it used the same index in both cases, and the index scan was reasonably fast (compared to your goal), but the heap component was slow. I suggest to run VACUUM FREEZE on the table, to try to encourage index only scan. If that works, you should condider setting aggressive autovacuum parameter, at least for the table: ALTER TABLE subscriptions SET (AUTOVACUUM_VACUUM_SCALE_FACTOR=0.005); -- And possibly lower value of autovacuum_freeze_max_age Or, running manual vacuum possibly during quiet hours (possibly setting vacuum_freeze_table_age to encourage aggressive vacuum). > Even an approximate count would be enough. You can SELECT reltuples FROM pg_class WHERE oid='subscriptions'::oid, but its accuracy depends on frequency of vacuum (and if a large delete/insert happened since the most recent vacuum/analyze). Justin
