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From: Kirill Reshke <[email protected]>
To: pgsql-hackers <[email protected]>
Subject: Re: Fix gistkillitems & add regression test to microvacuum
Date: Thu, 15 Jan 2026 12:46:44 +0500
Message-ID: <CALdSSPgPs=gKWkKN0=4yBd49FBY=ijxBz4YGV64vfVMK7YQhpw@mail.gmail.com> (raw)
In-Reply-To: <CALdSSPgZWX_D8+Fx4YQqRN5eW5iSx_rJdqQhCfdWTvqKXVfJ4w@mail.gmail.com>
References: <CALdSSPgZWX_D8+Fx4YQqRN5eW5iSx_rJdqQhCfdWTvqKXVfJ4w@mail.gmail.com>

On Thu, 15 Jan 2026 at 12:00, Kirill Reshke <[email protected]> wrote:
>
> Hi hackers.
>
> While looking at [0] I noticed that XLOG_GIST_DELETE &  XLOG_GIST_PAGE_DELETE
> records are not covered.
>
> This thread addresses XLOG_GIST_DELETE, which is also known as a
> microvacuum feature.
>
> test.sql contains regression test that trigger this code to be
> exercised in stream_regress.pl TAP test.
>
> Test is as follows: we create a gist index on the table, then we
> insert exactly 407 records, making the root page full (next insert
> will trigger page split). Then I delete all tuples from relation and
> trigger Index Only scan to do kill-on-select (killtuples). It marks
> gist 0 page (which is root and is leaf) as has_garbage. Then, the next
> insertion triggers xlog_gist_delete record.
>
> To verify this I use pageinspect and pg_waldimp (locally). Also this
> test is dependent on block size being 8192 which is not good.
>
>
> And all of this does not work actually without v1-0001, because there
> is a bug in GiST which does not call gistkillitmes for the very first
> (root) page.
>
> There is also test2.sql which inserts a single tuple, not 407. It can
> be used to verify v1-0001.
>
> [0] coverage.postgresql.org/src/backend/access/gist/gistxlog.c.gcov.html
>
>
> --
> Best regards,
> Kirill Reshke

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