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commit    8171d2dae93d8463f2cbba0ce18e3f5c85cac096
Author:   Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date:     Mon Mar 10 15:07:38 2025 +0000
First released in: 18.0, 13.21, 14.18, 15.13, 16.9, 17.5

    Fix snapshot used in logical replication index lookup
    
    The function calls GetLatestSnapshot() to acquire a fresh snapshot,
    makes it active, and was meant to pass it to table_tuple_lock(), but
    instead called GetLatestSnapshot() again to acquire yet another
    snapshot. It was harmless because the heap AM and all other known
    table AMs ignore the 'snapshot' argument anyway, but let's be tidy.
    
    In the long run, this perhaps should be redesigned so that snapshot
    was not needed in the first place. The table AM API uses TID +
    snapshot as the unique identifier for the row version, which is
    questionable when the row came from an index scan with a Dirty
    snapshot. You might lock a different row version when you use a
    different snapshot in the table_tuple_lock() call (a fresh MVCC
    snapshot) than in the index scan (DirtySnapshot). However, in the heap
    AM and other AMs where the TID alone identifies the row version, it
    doesn't matter. So for now, just fix the obvious albeit harmless bug.
    
    This has been wrong ever since the table AM API was introduced in
    commit 5db6df0c01, so backpatch to all supported versions.
    
    Discussion: https://www.postgresql.org/message-id/83d243d6-ad8d-4307-8b51-2ee5844f6230@iki.fi
    Backpatch-through: 13


 src/backend/executor/execReplication.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index 42383ed299b..603af4eabe1 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -209,7 +209,7 @@ retry:
 
 		PushActiveSnapshot(GetLatestSnapshot());
 
-		res = table_tuple_lock(rel, &(outslot->tts_tid), GetLatestSnapshot(),
+		res = table_tuple_lock(rel, &(outslot->tts_tid), GetActiveSnapshot(),
 							   outslot,
 							   GetCurrentCommandId(false),
 							   lockmode,


[parent: 778f9dd0d2aa]