From: Tom Lane <tgl@sss.pgh.pa.us>
To: efremov20081@gmail.com
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18330: The query planner chooses the wrong plan when using the parallel aggregation function
Date: Sun, 04 Feb 2024 19:16:40 -0500
Message-ID: <4148241.1707092200@sss.pgh.pa.us> (raw)
In-Reply-To: <18330-1823d6d59e6936c3@postgresql.org>
References: <18330-1823d6d59e6936c3@postgresql.org>
PG Bug reporting form <noreply@postgresql.org> writes:
> Below is an example of queries. It shows that the query planner chooses
> sequential aggregation instead of parallel, although limit should not have
> affected this.
On what grounds do you assert that LIMIT can be parallelized?
AFAICS it has to be done by a single process to ensure that the
limit is enforced accurately. So LIMIT below an aggregation
removes the opportunity to parallelize the aggregation.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, efremov20081@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18330: The query planner chooses the wrong plan when using the parallel aggregation function
In-Reply-To: <4148241.1707092200@sss.pgh.pa.us>
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