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help / color / mirror / Atom feedFrom: Kirill Reshke <[email protected]>
To: pgsql-hackers <[email protected]>
Subject: Fix gistkillitems & add regression test to microvacuum
Date: Thu, 15 Jan 2026 12:00:38 +0500
Message-ID: <CALdSSPgZWX_D8+Fx4YQqRN5eW5iSx_rJdqQhCfdWTvqKXVfJ4w@mail.gmail.com> (raw)
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
Attachments:
[application/octet-stream] test2.sql (501B, 2-test2.sql)
download
[application/octet-stream] test.sql (529B, 3-test.sql)
download
[application/octet-stream] v1-0001-Fix-gistkillitems-for-GiST-ROOT-page.patch (1.6K, 4-v1-0001-Fix-gistkillitems-for-GiST-ROOT-page.patch)
download | inline diff:
From 84b0fb6e1ce58c7b917fbcc32e73cadcd265d535 Mon Sep 17 00:00:00 2001
From: reshke <[email protected]>
Date: Thu, 15 Jan 2026 06:34:42 +0000
Subject: [PATCH v1] Fix gistkillitems for GiST ROOT page.
---
src/backend/access/gist/gist.c | 1 +
src/backend/access/gist/gistget.c | 6 +++---
2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 9c219cadf07..2f341df9058 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -1681,6 +1681,7 @@ gistprunepage(Relation rel, Page page, Buffer buffer, Relation heapRel)
maxoff;
Assert(GistPageIsLeaf(page));
+ Assert(BufferIsLockedByMeInMode(buffer, BUFFER_LOCK_EXCLUSIVE));
/*
* Scan over all items to see which ones need to be deleted according to
diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
index 11b214eb99b..7dc34680e2d 100644
--- a/src/backend/access/gist/gistget.c
+++ b/src/backend/access/gist/gistget.c
@@ -407,6 +407,9 @@ gistScanPage(IndexScanDesc scan, GISTSearchItem *pageItem,
*/
so->curPageLSN = BufferGetLSNAtomic(buffer);
+ /* save current item BlockNumber for gistkillitems() call */
+ so->curBlkno = pageItem->blkno;
+
/*
* check all tuples on page
*/
@@ -722,9 +725,6 @@ gistgettuple(IndexScanDesc scan, ScanDirection dir)
CHECK_FOR_INTERRUPTS();
- /* save current item BlockNumber for next gistkillitems() call */
- so->curBlkno = item->blkno;
-
/*
* While scanning a leaf page, ItemPointers of matching heap
* tuples are stored in so->pageData. If there are any on
--
2.43.0
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