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commit    ee3838b1d35cffec21ca40dbfc409ec40ddf3e28
Author:   Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date:     Fri Mar 04 13:37:09 2011 +0000
First released in: 9.1.0

    You must hold a lock on the heap page when you call
    CheckForSerializableConflictOut(), because it can set hint bits.
    
    YAMAMOTO Takashi


 src/backend/access/heap/heapam.c     | 4 ++--
 src/backend/storage/lmgr/predicate.c | 7 ++++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 7dcc6015de9..89697f6ff5e 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -1472,10 +1472,10 @@ heap_fetch(Relation relation,
 	if (valid)
 		PredicateLockTuple(relation, tuple);
 
-	LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
-
 	CheckForSerializableConflictOut(valid, relation, tuple, buffer);
 
+	LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+
 	if (valid)
 	{
 		/*
diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c
index aa657fab579..700c0db9278 100644
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -3366,9 +3366,10 @@ XidIsConcurrent(TransactionId xid)
  * If the transactions overlap (i.e., they cannot see each other's writes),
  * then we have a conflict out.
  *
- * This function should be called just about anywhere in heapam.c that a
- * tuple has been read.  There is currently no known reason to call this
- * function from an index AM.
+ * This function should be called just about anywhere in heapam.c where a
+ * tuple has been read. The caller must hold at least a shared lock on the
+ * buffer, because this function might set hint bits on the tuple. There is
+ * currently no known reason to call this function from an index AM.
  */
 void
 CheckForSerializableConflictOut(const bool visible, const Relation relation,


[parent: 12bf602f3fe9]