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From: Robert Haas <[email protected]>
To: Andres Freund <[email protected]>
Cc: Drouvot, Bertrand <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: Ibrar Ahmed <[email protected]>
Cc: Amit Khandekar <[email protected]>
Cc: [email protected]
Cc: tushar <[email protected]>
Cc: Rahila Syed <[email protected]>
Cc: pgsql-hackers <[email protected]>
Subject: Re: Minimal logical decoding on standbys
Date: Tue, 20 Dec 2022 16:41:54 -0500
Message-ID: <CA+TgmoYTTsxP8y6uknZvCBNCRq+1FJ4zGbX8Px1TGW459fGsaQ@mail.gmail.com> (raw)
In-Reply-To: <CA+TgmoaOsoQuXEo6gMq0GP8SyvCaS=ptYqdYc0uzDMoeShf_nw@mail.gmail.com>
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On Tue, Dec 20, 2022 at 3:39 PM Robert Haas <[email protected]> wrote:
> I think this might be the only WAL record type where there's a
> problem, but I haven't fully confirmed that yet.

It's not. GIST has the same issue. The same test case demonstrates the
problem there, if you substitute this test script for
kpt_hash_setup.sql and possibly also run it for somewhat longer. One
might think that this wouldn't be a problem, because the comments for
gistxlogDelete say this:

     /*
      * In payload of blk 0 : todelete OffsetNumbers
      */

But it's not in the payload of blk 0. It follows the main payload.

This is the reverse of xl_heap_freeze_page, which claims that freeze
plans and offset numbers follow, but they don't: they're in the data
for block 0. xl_btree_delete is also wrong, claiming that the data
follows when it's really attached to block 0. I guess whatever else we
do here, we should fix the comments.

Bottom line is that I think the two cases that have alignment issues
as coded are xl_hash_vacuum_one_page and gistxlogDelete. Everything
else is OK, as far as I can tell right now.

-- 
Robert Haas
EDB: http://www.enterprisedb.com


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