Hello, Hou zj!
> In my test, if the tuple is updated and new tuple is in the same page,
> heapam_index_fetch_tuple should find the new tuple using HOT chain. So,
it's a
> bit unclear to me how the updated tuple is missing. Maybe I missed some
other
> conditions for this issue.
Yeah, I think the pgbench-based reproducer may also cause page splits in
btree.
But we may add an index to the table to disable HOT.
I have attached a reproducer for this case using a spec and injection
points.
I hope it helps, check the attached files.
Best regards,
Mikhail.
From e3c1beb4d2739fb3b1cb7e068a7ef91b0da61fc6 Mon Sep 17 00:00:00 2001
From: nkey <n...@toloka.ai>
Date: Mon, 12 Aug 2024 13:07:15 +0200
Subject: [PATCH v2 2/2] additional test spec to reproduce dirty snapshot scan
issue
---
src/backend/access/index/indexam.c | 8 ++++
src/backend/executor/execIndexing.c | 1 +
src/test/modules/injection_points/Makefile | 2 +-
.../expected/dirty_index_scan.out | 39 +++++++++++++++++
src/test/modules/injection_points/meson.build | 1 +
.../specs/dirty_index_scan.spec | 43 +++++++++++++++++++
6 files changed, 93 insertions(+), 1 deletion(-)
create mode 100644 src/test/modules/injection_points/expected/dirty_index_scan.out
create mode 100644 src/test/modules/injection_points/specs/dirty_index_scan.spec
diff --git a/src/backend/access/index/indexam.c b/src/backend/access/index/indexam.c
index dcd04b813d..78b3a58b3b 100644
--- a/src/backend/access/index/indexam.c
+++ b/src/backend/access/index/indexam.c
@@ -57,6 +57,7 @@
#include "utils/ruleutils.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
+#include "utils/injection_point.h"
/* ----------------------------------------------------------------
@@ -694,6 +695,13 @@ index_getnext_slot(IndexScanDesc scan, ScanDirection direction, TupleTableSlot *
* the index.
*/
Assert(ItemPointerIsValid(&scan->xs_heaptid));
+#ifdef USE_INJECTION_POINTS
+ if (!IsCatalogRelationOid(scan->indexRelation->rd_id))
+ {
+ INJECTION_POINT("index_getnext_slot_before_fetch");
+ }
+#endif
+
if (index_fetch_heap(scan, slot))
return true;
}
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 45767b4e20..479f145d99 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -775,6 +775,7 @@ check_exclusion_or_unique_constraint(Relation heap, Relation index,
* May have to restart scan from this point if a potential conflict is
* found.
*/
+ INJECTION_POINT("check_exclusion_or_unique_constraint_before_index_scan");
retry:
conflict = false;
found_self = false;
diff --git a/src/test/modules/injection_points/Makefile b/src/test/modules/injection_points/Makefile
index 2ffd2f77ed..981dff4e6f 100644
--- a/src/test/modules/injection_points/Makefile
+++ b/src/test/modules/injection_points/Makefile
@@ -9,7 +9,7 @@ PGFILEDESC = "injection_points - facility for injection points"
REGRESS = injection_points
REGRESS_OPTS = --dlpath=$(top_builddir)/src/test/regress
-ISOLATION = inplace
+ISOLATION = inplace dirty_index_scan
# The injection points are cluster-wide, so disable installcheck
NO_INSTALLCHECK = 1
diff --git a/src/test/modules/injection_points/expected/dirty_index_scan.out b/src/test/modules/injection_points/expected/dirty_index_scan.out
new file mode 100644
index 0000000000..249e69cb72
--- /dev/null
+++ b/src/test/modules/injection_points/expected/dirty_index_scan.out
@@ -0,0 +1,39 @@
+Parsed test spec with 3 sessions
+
+starting permutation: s1_s1 s3_s1 s2_s1 s3_s2
+injection_points_attach
+-----------------------
+
+(1 row)
+
+step s1_s1: INSERT INTO test.tbl VALUES(42, 1) on conflict(i) do update set n = EXCLUDED.n + 1; <waiting ...>
+step s3_s1:
+ SELECT injection_points_wakeup('check_exclusion_or_unique_constraint_before_index_scan');
+ SELECT injection_points_detach('check_exclusion_or_unique_constraint_before_index_scan');
+
+injection_points_wakeup
+-----------------------
+
+(1 row)
+
+injection_points_detach
+-----------------------
+
+(1 row)
+
+step s2_s1: UPDATE test.tbl SET n = n + 1 WHERE i = 42;
+step s3_s2:
+ SELECT injection_points_wakeup('index_getnext_slot_before_fetch');
+ SELECT injection_points_detach('index_getnext_slot_before_fetch');
+
+injection_points_wakeup
+-----------------------
+
+(1 row)
+
+injection_points_detach
+-----------------------
+
+(1 row)
+
+step s1_s1: <... completed>
diff --git a/src/test/modules/injection_points/meson.build b/src/test/modules/injection_points/meson.build
index 3c23c14d81..4969952797 100644
--- a/src/test/modules/injection_points/meson.build
+++ b/src/test/modules/injection_points/meson.build
@@ -40,6 +40,7 @@ tests += {
'isolation': {
'specs': [
'inplace',
+ 'dirty_index_scan',
],
},
}
diff --git a/src/test/modules/injection_points/specs/dirty_index_scan.spec b/src/test/modules/injection_points/specs/dirty_index_scan.spec
new file mode 100644
index 0000000000..17c5ec37e6
--- /dev/null
+++ b/src/test/modules/injection_points/specs/dirty_index_scan.spec
@@ -0,0 +1,43 @@
+setup
+{
+ CREATE EXTENSION injection_points;
+ CREATE SCHEMA test;
+ CREATE UNLOGGED TABLE test.tbl(i int primary key, n int);
+ CREATE INDEX tbl_n_idx ON test.tbl(n);
+ INSERT INTO test.tbl VALUES(42,1);
+}
+
+teardown
+{
+ DROP SCHEMA test CASCADE;
+ DROP EXTENSION injection_points;
+}
+
+session s1
+setup {
+ SELECT injection_points_set_local();
+ SELECT injection_points_attach('check_exclusion_or_unique_constraint_no_conflict', 'error');
+ SELECT injection_points_attach('check_exclusion_or_unique_constraint_before_index_scan', 'wait');
+ SELECT injection_points_attach('index_getnext_slot_before_fetch', 'wait');
+}
+
+step s1_s1 { INSERT INTO test.tbl VALUES(42, 1) on conflict(i) do update set n = EXCLUDED.n + 1; }
+
+session s2
+step s2_s1 { UPDATE test.tbl SET n = n + 1 WHERE i = 42; }
+
+session s3
+step s3_s1 {
+ SELECT injection_points_wakeup('check_exclusion_or_unique_constraint_before_index_scan');
+ SELECT injection_points_detach('check_exclusion_or_unique_constraint_before_index_scan');
+}
+step s3_s2 {
+ SELECT injection_points_wakeup('index_getnext_slot_before_fetch');
+ SELECT injection_points_detach('index_getnext_slot_before_fetch');
+}
+
+permutation
+ s1_s1
+ s3_s1
+ s2_s1
+ s3_s2
\ No newline at end of file
--
2.34.1
From b639379c393c70ca322bab57222513e71c96ad78 Mon Sep 17 00:00:00 2001
From: nkey <n...@toloka.ai>
Date: Fri, 2 Aug 2024 16:20:32 +0200
Subject: [PATCH v2 1/2] fix for lost record in case of DirtySnapshot index
scans + docs + test
---
contrib/pgstattuple/pgstattuple.c | 2 +-
src/backend/access/heap/heapam_handler.c | 2 +-
src/backend/access/heap/heapam_visibility.c | 20 +++++++-
src/backend/access/nbtree/README | 10 ++++
src/backend/access/nbtree/nbtinsert.c | 2 +-
src/backend/access/transam/varsup.c | 11 +++++
src/backend/executor/execIndexing.c | 29 +++++++++++-
src/backend/executor/execReplication.c | 26 +++++++++-
src/backend/replication/logical/origin.c | 2 +-
src/include/access/transam.h | 16 +++++++
src/include/utils/snapmgr.h | 8 +++-
src/include/utils/snapshot.h | 5 +-
.../test_misc/t/006_dirty_index_scan.pl | 47 +++++++++++++++++++
13 files changed, 168 insertions(+), 12 deletions(-)
create mode 100644 src/test/modules/test_misc/t/006_dirty_index_scan.pl
diff --git a/contrib/pgstattuple/pgstattuple.c b/contrib/pgstattuple/pgstattuple.c
index 3bd8b96197..4d1b469d8e 100644
--- a/contrib/pgstattuple/pgstattuple.c
+++ b/contrib/pgstattuple/pgstattuple.c
@@ -332,7 +332,7 @@ pgstat_heap(Relation rel, FunctionCallInfo fcinfo)
scan = table_beginscan_strat(rel, SnapshotAny, 0, NULL, true, false);
hscan = (HeapScanDesc) scan;
- InitDirtySnapshot(SnapshotDirty);
+ InitDirtySnapshot(SnapshotDirty, NULL);
nblocks = hscan->rs_nblocks; /* # blocks to be scanned */
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index 6f8b1b7929..7ea4b205d5 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -404,7 +404,7 @@ tuple_lock_retry:
*
* Loop here to deal with updated or busy tuples
*/
- InitDirtySnapshot(SnapshotDirty);
+ InitDirtySnapshot(SnapshotDirty, NULL);
for (;;)
{
if (ItemPointerIndicatesMovedPartitions(tid))
diff --git a/src/backend/access/heap/heapam_visibility.c b/src/backend/access/heap/heapam_visibility.c
index 9243feed01..91de5dcea1 100644
--- a/src/backend/access/heap/heapam_visibility.c
+++ b/src/backend/access/heap/heapam_visibility.c
@@ -719,6 +719,12 @@ HeapTupleSatisfiesUpdate(HeapTuple htup, CommandId curcid,
return TM_Deleted; /* deleted by other */
}
+inline static void UpdateDirtyMaxXmax(Snapshot snapshot, TransactionId xmax)
+{
+ if (snapshot->xip != NULL)
+ snapshot->xip[0] = TransactionIdNewer(xmax, snapshot->xip[0]);
+}
+
/*
* HeapTupleSatisfiesDirty
* True iff heap tuple is valid including effects of open transactions.
@@ -737,7 +743,9 @@ HeapTupleSatisfiesUpdate(HeapTuple htup, CommandId curcid,
* Similarly for snapshot->xmax and the tuple's xmax. If the tuple was
* inserted speculatively, meaning that the inserter might still back down
* on the insertion without aborting the whole transaction, the associated
- * token is also returned in snapshot->speculativeToken.
+ * token is also returned in snapshot->speculativeToken. If xip is != NULL
+ * xip[0] may be set to xid of deleter if it newer than previously store
+ * value.
*/
static bool
HeapTupleSatisfiesDirty(HeapTuple htup, Snapshot snapshot,
@@ -750,6 +758,10 @@ HeapTupleSatisfiesDirty(HeapTuple htup, Snapshot snapshot,
snapshot->xmin = snapshot->xmax = InvalidTransactionId;
snapshot->speculativeToken = 0;
+ /*
+ * We intentionally keep snapshot->xip values unchanged as they should
+ * be reset by logic out of the single heap fetch.
+ */
if (!HeapTupleHeaderXminCommitted(tuple))
{
@@ -870,6 +882,7 @@ HeapTupleSatisfiesDirty(HeapTuple htup, Snapshot snapshot,
{
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
return true;
+ UpdateDirtyMaxXmax(snapshot, HeapTupleHeaderGetRawXmax(tuple));
return false; /* updated by other */
}
@@ -893,7 +906,10 @@ HeapTupleSatisfiesDirty(HeapTuple htup, Snapshot snapshot,
return true;
}
if (TransactionIdDidCommit(xmax))
+ {
+ UpdateDirtyMaxXmax(snapshot, xmax);
return false;
+ }
/* it must have aborted or crashed */
return true;
}
@@ -902,6 +918,7 @@ HeapTupleSatisfiesDirty(HeapTuple htup, Snapshot snapshot,
{
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
return true;
+ UpdateDirtyMaxXmax(snapshot, HeapTupleHeaderGetRawXmax(tuple));
return false;
}
@@ -931,6 +948,7 @@ HeapTupleSatisfiesDirty(HeapTuple htup, Snapshot snapshot,
SetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
HeapTupleHeaderGetRawXmax(tuple));
+ UpdateDirtyMaxXmax(snapshot, HeapTupleHeaderGetRawXmax(tuple));
return false; /* updated by other */
}
diff --git a/src/backend/access/nbtree/README b/src/backend/access/nbtree/README
index 52e646c7f7..6de72a29ca 100644
--- a/src/backend/access/nbtree/README
+++ b/src/backend/access/nbtree/README
@@ -489,6 +489,16 @@ on the leaf page at all when the page's LSN has changed. (That won't work
with an unlogged index, so for now we don't ever apply the "don't hold
onto pin" optimization there.)
+Despite the locking protocol in place, it is still possible to receive an
+incorrect result during non-MVCC scans. This issue can occur if a concurrent
+transaction deletes a tuple and inserts a new tuple with a new TID in the
+same page. If the scan has already visited the page and cached its content
+in the buffer cache, it might skip the old tuple due to deletion and miss
+the new tuple because of the cache. This is a known limitation of the
+SnapshotDirty and SnapshotAny non-MVCC scans. However, for SnapshotDirty,
+it is possible to work around this limitation by using the returned max(xmax)
+to compare it with the latest committed transaction before the scan started.
+
Fastpath For Index Insertion
----------------------------
diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c
index 7e8902e48c..943aee087a 100644
--- a/src/backend/access/nbtree/nbtinsert.c
+++ b/src/backend/access/nbtree/nbtinsert.c
@@ -427,7 +427,7 @@ _bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
/* Assume unique until we find a duplicate */
*is_unique = true;
- InitDirtySnapshot(SnapshotDirty);
+ InitDirtySnapshot(SnapshotDirty, NULL);
page = BufferGetPage(insertstate->buf);
opaque = BTPageGetOpaque(page);
diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fb6a86afcb..52109635b4 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -296,6 +296,17 @@ ReadNextFullTransactionId(void)
return fullXid;
}
+FullTransactionId ReadLastCompletedFullTransactionId(void)
+{
+ FullTransactionId fullXid;
+
+ LWLockAcquire(XidGenLock, LW_SHARED);
+ fullXid = TransamVariables->latestCompletedXid;
+ LWLockRelease(XidGenLock);
+
+ return fullXid;
+}
+
/*
* Advance nextXid to the value after a given xid. The epoch is inferred.
* This must only be called during recovery or from two-phase start-up code.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..45767b4e20 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -115,6 +115,7 @@
#include "nodes/nodeFuncs.h"
#include "storage/lmgr.h"
#include "utils/snapmgr.h"
+#include "utils/injection_point.h"
/* waitMode argument to check_exclusion_or_unique_constraint() */
typedef enum
@@ -702,6 +703,8 @@ check_exclusion_or_unique_constraint(Relation heap, Relation index,
IndexScanDesc index_scan;
ScanKeyData scankeys[INDEX_MAX_KEYS];
SnapshotData DirtySnapshot;
+ TransactionId maxXmax,
+ latestCompletedXid;
int i;
bool conflict;
bool found_self;
@@ -738,9 +741,10 @@ check_exclusion_or_unique_constraint(Relation heap, Relation index,
/*
* Search the tuples that are in the index for any violations, including
- * tuples that aren't visible yet.
+ * tuples that aren't visible yet. Also, detect cases index scan skip the
+ * tuple in case of parallel update after index page content was cached.
*/
- InitDirtySnapshot(DirtySnapshot);
+ InitDirtySnapshot(DirtySnapshot, &maxXmax);
for (i = 0; i < indnkeyatts; i++)
{
@@ -774,6 +778,12 @@ check_exclusion_or_unique_constraint(Relation heap, Relation index,
retry:
conflict = false;
found_self = false;
+ /*
+ * Each time we retry - remember last completed transaction before start
+ * of the scan. Aso reset maxXmax.
+ */
+ latestCompletedXid = XidFromFullTransactionId(ReadLastCompletedFullTransactionId());
+ maxXmax = InvalidTransactionId;
index_scan = index_beginscan(heap, index, &DirtySnapshot, indnkeyatts, 0);
index_rescan(index_scan, scankeys, indnkeyatts, NULL, 0);
@@ -889,6 +899,19 @@ retry:
}
index_endscan(index_scan);
+ /*
+ * Check for the case when index scan fetched records before some other
+ * transaction deleted tuple and inserted a new one.
+ */
+ if (!conflict && TransactionIdIsValid(maxXmax) && !TransactionIdIsCurrentTransactionId(maxXmax))
+ {
+ /*
+ * If we have skipped some tuple because it was deleted, but deletion happened after
+ * start of the index scan - retry to be sure.
+ */
+ if (TransactionIdPrecedes(latestCompletedXid, maxXmax))
+ goto retry;
+ }
/*
* Ordinarily, at this point the search should have found the originally
@@ -902,6 +925,8 @@ retry:
ExecDropSingleTupleTableSlot(existing_slot);
+ if (!conflict)
+ INJECTION_POINT("check_exclusion_or_unique_constraint_no_conflict");
return !conflict;
}
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..fbddb6442b 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -183,6 +183,8 @@ RelationFindReplTupleByIndex(Relation rel, Oid idxoid,
IndexScanDesc scan;
SnapshotData snap;
TransactionId xwait;
+ TransactionId maxXmax,
+ latestCompletedXid;
Relation idxrel;
bool found;
TypeCacheEntry **eq = NULL;
@@ -193,7 +195,7 @@ RelationFindReplTupleByIndex(Relation rel, Oid idxoid,
isIdxSafeToSkipDuplicates = (GetRelationIdentityOrPK(rel) == idxoid);
- InitDirtySnapshot(snap);
+ InitDirtySnapshot(snap, &maxXmax);
/* Build scan key. */
skey_attoff = build_replindex_scan_key(skey, rel, idxrel, searchslot);
@@ -203,6 +205,12 @@ RelationFindReplTupleByIndex(Relation rel, Oid idxoid,
retry:
found = false;
+ /*
+ * Each time we retry - remember last completed transaction before start
+ * of the scan. Aso reset maxXmax.
+ */
+ maxXmax = InvalidTransactionId;
+ latestCompletedXid = XidFromFullTransactionId(ReadLastCompletedFullTransactionId());
index_rescan(scan, skey, skey_attoff, NULL, 0);
@@ -242,6 +250,20 @@ retry:
break;
}
+ /*
+ * Check for the case when index scan fetched records before some other
+ * transaction deleted tuple and inserted a new one.
+ */
+ if (!found && TransactionIdIsValid(maxXmax) && !TransactionIdIsCurrentTransactionId(maxXmax))
+ {
+ /*
+ * If we have skipped some tuple because it was deleted, but deletion happened after
+ * start of the index scan - retry to be sure.
+ */
+ if (TransactionIdPrecedes(latestCompletedXid, maxXmax))
+ goto retry;
+ }
+
/* Found tuple, try to lock it in the lockmode. */
if (found)
{
@@ -391,7 +413,7 @@ RelationFindReplTupleSeq(Relation rel, LockTupleMode lockmode,
eq = palloc0(sizeof(*eq) * outslot->tts_tupleDescriptor->natts);
/* Start a heap scan. */
- InitDirtySnapshot(snap);
+ InitDirtySnapshot(snap, NULL);
scan = table_beginscan(rel, &snap, 0, NULL);
scanslot = table_slot_create(rel, NULL);
diff --git a/src/backend/replication/logical/origin.c b/src/backend/replication/logical/origin.c
index 419e4814f0..04ba0d9ba1 100644
--- a/src/backend/replication/logical/origin.c
+++ b/src/backend/replication/logical/origin.c
@@ -278,7 +278,7 @@ replorigin_create(const char *roname)
* to the exclusive lock there's no danger that new rows can appear while
* we're checking.
*/
- InitDirtySnapshot(SnapshotDirty);
+ InitDirtySnapshot(SnapshotDirty, NULL);
rel = table_open(ReplicationOriginRelationId, ExclusiveLock);
diff --git a/src/include/access/transam.h b/src/include/access/transam.h
index 28a2d287fd..aae0ad90c2 100644
--- a/src/include/access/transam.h
+++ b/src/include/access/transam.h
@@ -288,6 +288,7 @@ extern void VarsupShmemInit(void);
extern FullTransactionId GetNewTransactionId(bool isSubXact);
extern void AdvanceNextFullTransactionIdPastXid(TransactionId xid);
extern FullTransactionId ReadNextFullTransactionId(void);
+extern FullTransactionId ReadLastCompletedFullTransactionId(void);
extern void SetTransactionIdLimit(TransactionId oldest_datfrozenxid,
Oid oldest_datoid);
extern void AdvanceOldestClogXid(TransactionId oldest_datfrozenxid);
@@ -344,6 +345,21 @@ TransactionIdOlder(TransactionId a, TransactionId b)
return b;
}
+/* return the newer of the two IDs */
+static inline TransactionId
+TransactionIdNewer(TransactionId a, TransactionId b)
+{
+ if (!TransactionIdIsValid(a))
+ return b;
+
+ if (!TransactionIdIsValid(b))
+ return a;
+
+ if (TransactionIdPrecedes(a, b))
+ return b;
+ return a;
+}
+
/* return the older of the two IDs, assuming they're both normal */
static inline TransactionId
NormalTransactionIdOlder(TransactionId a, TransactionId b)
diff --git a/src/include/utils/snapmgr.h b/src/include/utils/snapmgr.h
index 9398a84051..5e6f3a7e76 100644
--- a/src/include/utils/snapmgr.h
+++ b/src/include/utils/snapmgr.h
@@ -36,9 +36,13 @@ extern PGDLLIMPORT SnapshotData CatalogSnapshotData;
* We don't provide a static SnapshotDirty variable because it would be
* non-reentrant. Instead, users of that snapshot type should declare a
* local variable of type SnapshotData, and initialize it with this macro.
+ * pxid is optional and can be NULL. If it is not NULL, pxid[0] will be set
+ * to the transaction ID of deleting transaction if the tuple is deleted
+ * and it newer than pxid[0].
*/
-#define InitDirtySnapshot(snapshotdata) \
- ((snapshotdata).snapshot_type = SNAPSHOT_DIRTY)
+#define InitDirtySnapshot(snapshotdata, pxid) \
+ ((snapshotdata).snapshot_type = SNAPSHOT_DIRTY, \
+ (snapshotdata).xip = (pxid))
/*
* Similarly, some initialization is required for a NonVacuumable snapshot.
diff --git a/src/include/utils/snapshot.h b/src/include/utils/snapshot.h
index 8d1e31e888..a68114e500 100644
--- a/src/include/utils/snapshot.h
+++ b/src/include/utils/snapshot.h
@@ -96,7 +96,10 @@ typedef enum SnapshotType
* xmax. If the tuple was inserted speculatively, meaning that the
* inserter might still back down on the insertion without aborting the
* whole transaction, the associated token is also returned in
- * snapshot->speculativeToken. See also InitDirtySnapshot().
+ * snapshot->speculativeToken. If xip is non-NULL, the xid of the
+ * deleting transaction is stored into xip[0] if it newer than existing
+ * xip[0] value.
+ * See also InitDirtySnapshot().
* -------------------------------------------------------------------------
*/
SNAPSHOT_DIRTY,
diff --git a/src/test/modules/test_misc/t/006_dirty_index_scan.pl b/src/test/modules/test_misc/t/006_dirty_index_scan.pl
new file mode 100644
index 0000000000..4d116e659e
--- /dev/null
+++ b/src/test/modules/test_misc/t/006_dirty_index_scan.pl
@@ -0,0 +1,47 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+# Test issue with lost tuple in case of DirtySnapshot index scans
+use strict;
+use warnings;
+
+use Config;
+use Errno;
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+if ($ENV{enable_injection_points} ne 'yes')
+{
+ plan skip_all => 'Injection points not supported by this build';
+}
+
+my ($node, $result);
+$node = PostgreSQL::Test::Cluster->new('DirtyScan_test');
+$node->init;
+$node->append_conf('postgresql.conf', 'fsync = off');
+$node->append_conf('postgresql.conf', 'autovacuum = off');
+$node->start;
+$node->safe_psql('postgres', q(CREATE EXTENSION injection_points));
+$node->safe_psql('postgres', q(CREATE TABLE tbl(i int primary key, n int)));
+
+$node->safe_psql('postgres', q(INSERT INTO tbl VALUES(42,1)));
+$node->safe_psql('postgres', q(SELECT injection_points_attach('check_exclusion_or_unique_constraint_no_conflict', 'error')));
+
+$node->pgbench(
+ '--no-vacuum --client=40 --transactions=1000',
+ 0,
+ [qr{actually processed}],
+ [qr{^$}],
+ 'concurrent UPSERT',
+ {
+ 'on_conflicts' => q(
+ INSERT INTO tbl VALUES(42,1) on conflict(i) do update set n = EXCLUDED.n + 1;
+ )
+ });
+
+$node->safe_psql('postgres', q(SELECT injection_points_detach('check_exclusion_or_unique_constraint_no_conflict')));
+
+$node->stop;
+done_testing();
\ No newline at end of file
--
2.34.1
