>
>
> 3) Here's the query plan that I get after disabling the seq scan:
>
>
> QUERY PLAN
>
>
>
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Finalize Aggregate (cost=2183938.89..2183938.90 rows=1 width=8) (actual
> time=94972.253..94972.254 rows=1 loops=1)
>
> -> Gather (cost=2183938.16..2183938.87 rows=7 width=8) (actual
> time=94952.895..95132.626 rows=8 loops=1)
>
> Workers Planned: 7
>
> Workers Launched: 7
>
> -> Partial Aggregate (cost=2182938.16..2182938.17 rows=1
> width=8) (actual time=94950.958..94950.958 rows=1 loops=8)
>
> -> Parallel Bitmap Heap Scan on subscriptions
> (cost=50294.50..2180801.47 rows=854677 width=0) (actual
> time=1831.342..94895.208 rows=611828 loops=8)
>
> Recheck Cond: ((project_id = 123) AND (trashed_at IS
> NULL))
>
> Rows Removed by Index Recheck: 2217924
>
> Filter: (NOT (tags @> '{en}'::character varying[]))
>
> Rows Removed by Filter: 288545
>
> Heap Blocks: exact=120301 lossy=134269
>
> -> Bitmap Index Scan on
> index_subscriptions_on_project_id_and_tags (cost=0.00..48798.81
> rows=6518094 width=0) (actual time=1493.823..1493.823 rows=7203173 loops=1)
>
> Index Cond: (project_id = 123)
>
> Planning Time: 1.273 ms
>
> Execution Time: 95132.766 ms
>
> (15 rows)
>
What was the plan for the one that took 500ms? I don't see how it is
possible that this one is 180 times slower than that one. Maybe a hot
cache versus cold cache? Also, it seems weird to me that "trashed_at IS
NULL" shows up in the recheck but not in the original Index Cond.
Increasing work_mem can also help, but since the Bitmap Index Scan itself
took half the time there is only so much it can do.
Cheers,
Jeff
