Re: Documentation refinement for Parallel Scans

From: David Rowley <dgrowleyml(at)gmail(dot)com>
To: Zhang Mingli <zmlpostgres(at)gmail(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Documentation refinement for Parallel Scans
Date: 2022-10-20 06:33:34
Message-ID: CAApHDvrzaSUEyoEOORrZXvELddXaoit1e+Pp07qOu+9o6K390A@mail.gmail.com
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On Thu, 20 Oct 2022 at 16:03, Zhang Mingli <zmlpostgres(at)gmail(dot)com> wrote:
> As said in parallel.smgl:
>
> In a parallel sequential scan, the table's blocks will be divided among the cooperating processes. Blocks are handed out one at a time, so that access to the table remains sequential.

> Shall we update the documents?

Yeah, 56788d215 should have updated that. Seems I didn't expect that
level of detail in the docs. I've attached a patch to address this.

I didn't feel the need to go into too much detail about how the sizes
of the ranges are calculated. I tried to be brief, but I think I did
leave enough in there so that a reader will know that we don't just
make the range length <nblocks> / <nworkers>.

I'll push this soon if nobody has any other wording suggestions.

Thanks for the report.

David

Attachment Content-Type Size
fix_parallel_seqscan_docs.patch text/plain 786 bytes

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