Thanks for your response, Justin!
Here's the plan if we disable the custom_2 index. It uses the index I expect and it's much faster.
Here's a plan if we disable index scans. It uses both indexes and is much faster.
Here are the stats you asked for:
And here are the table stats for other_events_1004175222_pim_core_custom_2_8e65d072fbdd_idx and other_events_1004175222_pim_evdef_67951aef14bc_idx:
Thanks again for your help!
On Wed, Aug 11, 2021 at 8:38 AM Justin Pryzby <pryzby@xxxxxxxxxxxxx> wrote:
On Tue, Aug 10, 2021 at 12:47:20PM -0400, Matt Dupree wrote:
> Here's the plan: https://explain.depesz.com/s/uNGg
>
> Note that the index being used is
Could you show the plan if you force use of the intended index ?
For example by doing begin; DROP INDEX indexbeingused; explain thequery; rollback;
Or: begin; UPDATE pg_index SET indisvalid=false WHERE indexrelid='indexbeingused'::regclass explain thequery; rollback;
Could you show the table statistics for the time, user_id, and type columns on
all 4 tables ?
| SELECT (SELECT sum(x) FROM unnest(most_common_freqs) x) frac_MCV, tablename, attname, inherited, null_frac, n_distinct, array_length(most_common_vals,1) n_mcv, array_length(histogram_bounds,1) n_hist, correlation FROM pg_stats WHERE attname='...' AND tablename='...' ORDER BY 1 DESC;
It might be interesting to see both query plans when index scans are disabled
and bitmap scan are used instead (this might be as simple as begin; SET LOCAL
enable_indexscan=off ...; rollback;);
> Also note that these child tables have 100s of partial indexes. You
> can find history on why we have things set up this way here
> <https://heap.io/blog/running-10-million-postgresql-indexes-in-production>.
I have read it before :)
> SELECT relname, relpages, reltuples, relallvisible, pg_table_size(oid)
> FROM pg_class WHERE relname = 'other_events_1004175222';
Could you also show the table stats for the two indexes ?
One problem is that the rowcount estimate is badly off:
| Index Scan using other_events_1004175222_pim_core_custom_2_8e65d072fbdd_idx on public.other_events_1004175222 (cost=0.57..1,213,327.64 rows=1,854,125 width=32) (actual time=450.588..29,057.269 rows=23 loops=1)
To my eyes, this looks like a typo ; it's used in the index predicate as well
as the query, but maybe it's still relevant ?
| #close_onborading
--
Justin
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