Re: Terribly slow query with very good plan? - Mailing list pgsql-performance
| From | Laurenz Albe |
|---|---|
| Subject | Re: Terribly slow query with very good plan? |
| Date | |
| Msg-id | 64f14cb61b82fc8bd2d03963d03b7da252b1ba59.camel@cybertec.at Whole thread Raw |
| In response to | Terribly slow query with very good plan? (Les <nagylzs@gmail.com>) |
| Responses |
Re: Terribly slow query with very good plan?
(Les <nagylzs@gmail.com>)
|
| List | 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..25414.969rows=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) (actualtime=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
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