Re[4]: Postgresql planning time too high

The CPU is at about 7% when I run the query and 5% are occupied by
postgresql.
CPU is Xeon E3 1240 v6 3.7Gh - not very good, but postgres is not
overloading it.

Tests are done on windows 2016 server so the next step was to try and
change the priority of all the postgresql procesess to realtime.
This setting had some effect as the planning time went down from
5114.959 ms to 2999.542 ms

And then I changed a single line and the planning time went from
2999.542 ms to 175.509 ms: I deleted the line "LIMIT 20 OFFSET 0"
Changing this line in the final query is not an option, can I do
something else to fix this?

Thank you.

------ Original Message ------
From: "Pavel Stehule" <pavel(dot)stehule(at)gmail(dot)com>
To: "Sterpu Victor" <victor(at)caido(dot)ro>
Cc: "Fırat Güleç" <firat(dot)gulec(at)hepsijet(dot)com>; "Pgsql Performance"
<pgsql-performance(at)lists(dot)postgresql(dot)org>
Sent: 2019-11-22 2:59:11 PM
Subject: Re: Re[2]: Postgresql planning time too high

>
>
>pá 22. 11. 2019 v 12:46 odesílatel Sterpu Victor <victor(at)caido(dot)ro>
>napsal:
>>No rows should be returned, DB is empty.
>>I'm testing now on a empty DB trying to find out how to improve this.
>>
>>In this query I have 3 joins like this:
>>
>>SELECT t1.id, t2.valid_from
>>FROM t1
>>JOIN t2 ON (t1.id_t1 = t1.id)
>>LEFT JOIN t3 ON (t3.id_t1 = t1.id AND t3.valid_from<t2.valid_from)
>>WHERE t3.id IS NULL
>>
>>If I delete these 3 joins than the planning time goes down from 5.482
>>ms to 754.708 ms but I'm not sure why this context is so demanding on
>>the planner.
>>I'm tryng now to make a materialized view that will allow me to stop
>>using the syntax above.
>
>This query is little bit crazy - it has more than 40 joins - but 700ms
>for planning is looks too much. Maybe your comp has slow CPU.
>
>Postgres has two planners - deterministic and genetic
>
> https://www.postgresql.org/docs/9.1/geqo-pg-intro.html
>
>Probably slow plan is related to deterministic planner.
>
>
>>
>>I reattached the same files, they should be fine like this.
>>
>>
>>
>>
>>------ Original Message ------
>>From: "Fırat Güleç" <firat(dot)gulec(at)hepsijet(dot)com>
>>To: "Sterpu Victor" <victor(at)caido(dot)ro>
>>Cc: pgsql-performance(at)lists(dot)postgresql(dot)org
>>Sent: 2019-11-22 1:35:15 PM
>>Subject: RE: Postgresql planning time too high
>>
>>>Hello Sterpu,
>>>
>>>
>>>
>>>First, please run vaccum for your Postgresql DB.
>>>
>>>
>>>
>>>No rows returned from your query. Could you double check your query
>>>criteria.
>>>
>>>
>>>
>>>After that could you send explain analyze again .
>>>
>>>
>>>
>>>Regards,
>>>
>>>
>>>
>>>FIRAT GÜLEÇ
>>>Infrastructure & Database Operations Manager
>>>firat(dot)gulec(at)hepsijet(dot)com
>>>
>>>
>>>
>>>M: 0 532 210 57 18
>>>İnönü Mh. Mimar Sinan Cd. No:3 Güzeller Org.San.Bölg. GEBZE / KOCAELİ
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>From: Sterpu Victor <victor(at)caido(dot)ro>
>>>Sent: Friday, November 22, 2019 2:21 PM
>>>To:pgsql-performance(at)lists(dot)postgresql(dot)org
>>>Subject: Postgresql planning time too high
>>>
>>>
>>>
>>>Hello
>>>
>>>
>>>
>>>I'm on a PostgreSQL 12.1 and I just restored a database from a
>>>backup.
>>>
>>>When I run a query I get a big execution time: 5.482 ms
>>>
>>>After running EXPLAIN ANALYZE I can see that the "Planning Time:
>>>5165.742 ms" and the "Execution Time: 6.244 ms".
>>>
>>>The database is new(no need to vacuum) and i'm the only one connected
>>>to it. I use a single partition on the harddrive.
>>>
>>>I also tried this on a postgresql 9.5 and the result was the same.
>>>
>>>I'm not sure what to do to improve this situation.
>>>
>>>The query and the explain is attached.
>>>
>>>
>>>
>>>Thank you
>>>
>>>
>>>
>>>