From: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
---|---|
To: | Les <nagylzs(at)gmail(dot)com>, pgsql-performance(at)lists(dot)postgresql(dot)org |
Subject: | Re: Terribly slow query with very good plan? |
Date: | 2022-02-04 09:18:43 |
Message-ID: | 64f14cb61b82fc8bd2d03963d03b7da252b1ba59.camel@cybertec.at |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
On Fri, 2022-02-04 at 10:11 +0100, Les wrote:
> EXPLAIN (ANALYZE, COSTS, VERBOSE, BUFFERS)
>
> select id, title,
> (exists (select f2.id from media.oo_file f2 where f2.relpath like f.relpath || '%')) as has_file
> from media.oo_folder f where f.parent_id is null
>
> QUERY PLAN |
> --------------------------------------------------------------------------------------------------------------------------------------------------------------+
> Index Scan using oo_folder_idx_parent on media.oo_folder f (cost=0.42..488.02 rows=20 width=26) (actual time=713.419..25414.969 rows=45 loops=1) |
> Output: f.id, f.title, (SubPlan 1) |
> Index Cond: (f.parent_id IS NULL) |
> Buffers: shared hit=7014170 |
> SubPlan 1 |
> -> Index Only Scan using oo_file_idx_relpath on media.oo_file f2 (cost=0.55..108499.27 rows=5381 width=0) (actual time=564.756..564.756 rows=0 loops=45)|
> Filter: (f2.relpath ~~ (f.relpath || '%'::text)) |
> Rows Removed by Filter: 792025 |
> Heap Fetches: 768960 |
> Buffers: shared hit=7014130 |
> Planning Time: 0.361 ms |
> Execution Time: 25415.088 ms |
>
> It also returns 45 rows, but in 25 seconds which is unacceptable.
You should create an index that supports LIKE; for example
CREATE INDEX ON media.oo_file (relpath COLLATE "C");
Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com
From | Date | Subject | |
---|---|---|---|
Next Message | Pavel Stehule | 2022-02-04 09:23:03 | Re: Terribly slow query with very good plan? |
Previous Message | Les | 2022-02-04 09:11:31 | Terribly slow query with very good plan? |