MIME-Version: 1.0
From: Kirill Reshke <reshkekirill@gmail.com>
Date: Thu, 15 Jan 2026 12:00:38 +0500
Message-ID: <CALdSSPgZWX_D8+Fx4YQqRN5eW5iSx_rJdqQhCfdWTvqKXVfJ4w@mail.gmail.com>
Subject: Fix gistkillitems & add regression test to microvacuum
To: pgsql-hackers <pgsql-hackers@postgresql.org>
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Archived-At: <https://www.postgresql.org/message-id/CALdSSPgZWX_D8%2BFx4YQqRN5eW5iSx_rJdqQhCfdWTvqKXVfJ4w%40mail.gmail.com>
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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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