Applies on top of v2-0001 and v2-0002 upthread.  Not for the CF bot.
Skip xmax == xmin and MultiXact xmax in the second hint.

diff --git a/src/backend/access/heap/heapam_visibility.c b/src/backend/access/heap/heapam_visibility.c
--- a/src/backend/access/heap/heapam_visibility.c
+++ b/src/backend/access/heap/heapam_visibility.c
@@ -1191,12 +1191,15 @@ HeapTupleSatisfiesVacuumHorizon(HeapTuple htup, Buffer buffer, TransactionId *de
 			 * from an updated one.
 			 */
 			if (!(tuple->t_infomask & HEAP_XMAX_INVALID) &&
+				!(tuple->t_infomask & HEAP_XMAX_IS_MULTI) &&
 				!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask) &&
 				!HeapTupleHeaderIsOnlyLocked(tuple))
 			{
 				TransactionId xmax = HeapTupleHeaderGetUpdateXid(tuple);
 
-				if (!TransactionIdIsInProgress(xmax) &&
+				/* xmax == xmin: xmax is in progress too, nothing to do */
+				if (!TransactionIdEquals(xmax, HeapTupleHeaderGetRawXmin(tuple)) &&
+					!TransactionIdIsInProgress(xmax) &&
 					!TransactionIdDidCommit(xmax))
 					SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
 								InvalidTransactionId);