Re: [HACKERS] [PATCH] Push limit to sort through a subquery
| От | Douglas Doole |
|---|---|
| Тема | Re: [HACKERS] [PATCH] Push limit to sort through a subquery |
| Дата | |
| Msg-id | CADE5jY+VaJgOxAhRXiUuj8BSO4FMj_Hrkba5dbXApvCokEi_-Q@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: [HACKERS] [PATCH] Push limit to sort through a subquery (Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>) |
| Ответы |
Re: [HACKERS] [PATCH] Push limit to sort through a subquery
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| Список | pgsql-hackers |
If you add this to the commitfest app, more people might look at it when the next commitfest opens.
I have added it. https://commitfest.postgresql.org/14/1119/
Also, it might help if you can provide a query/ies with numbers where this optimization shows improvement.
I can't provide the real queries where we encountered the problem because they are internal. However I showed a simplified version of the queries in my first post.
On our queries, the change made quite a difference - execution time dropped from 31.4 seconds to 7.2 seconds. Explain analyze also shows that memory use dropped significantly and we didn't have to spill the sort to disk
From:
-> Sort (cost=989.95..1013.27 rows=9326 width=30) (node_startup_time/loop=31328.891, node_total_time/loop: 31329.756 rows=2001 loops=1) Buffers: temp read=772 written=11201 lsm_bufmgr hits=3392 Sort Key: *** Sort Method: external merge Sort Space Used: 89592 Sort Space Type: Disk
To:
-> Sort (cost=989.95..1013.27 rows=9326 width=30) (node_startup_time/loop=7123.275, node_total_time/loop: 7123.504 rows=2001 loops=1) Buffers: lsm_bufmgr hits=3387 Sort Key: *** Sort Method: top-N heapsort Sort Space Used: 3256 Sort Space Type: Memory
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