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Re: Parallel hints in PostgreSQL with consistent perfromance - Mailing list pgsql-performance

From Jeff Janes
Subject Re: Parallel hints in PostgreSQL with consistent perfromance
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Msg-id CAMkU=1wjnBOxpiK1Wn4LyQ9OCh0wSHUo7VwrZqxfpRpRvTWdJg@mail.gmail.com
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In response to Parallel hints in PostgreSQL with consistent perfromance  (mohini mane <mohini.android@gmail.com>)
Responses Re: Parallel hints in PostgreSQL with consistent perfromance  (mohini mane <mohini.android@gmail.com>)
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On Wed, Dec 27, 2023 at 8:15 AM mohini mane <mohini.android@gmail.com> wrote:
Hello Team,
I observed that increasing the degree of parallel hint in the SELECT query did not show performance improvements.
Below are the details of sample execution with EXPLAIN ANALYZE

PostgreSQL doesn't have hints, unless you are using pg_hint_plan. Which you should say if you are.

Output:
PSQL query execution with hints 6 for 1st time => 203505.402 ms
PSQL query execution with hints 6 for 2nd time => 27920.272 ms
PSQL query execution with hints 6 for 3rd time => 27666.770 ms
Only 6 workers launched, and there is no reduction in execution time even after increasing the degree of parallel hints in select query.

All you are showing here is the effect of caching the data in memory.  You allude to changing the degree, but didn't show any results, or even describe what the change was.  Is 6 the base from which you increased, or is it the result of having done the increase?

Cheers,

Jeff

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