Add VacuumHorizonHook instead of just hint bits horizon

Author: akorotkov

src/backend/access/heap/heapam_visibility.c

@@ -80,7 +80,7 @@
 #include "utils/combocid.h"
 #include "utils/snapmgr.h"
 
-static TransactionId hint_bit_horizon = InvalidTransactionId;
+VacuumHorizonHookType VacuumHorizonHook = NULL;
 
 /*
  * SetHintBits()
@@ -130,10 +130,14 @@ SetHintBits(HeapTupleHeader tuple, Buffer buffer,
 		}
 	}
 
-	if (TransactionIdIsValid(hint_bit_horizon) &&
-		TransactionIdIsValid(xid) &&
-		TransactionIdFollows(xid, hint_bit_horizon))
-		return;
+	if (TransactionIdIsValid(xid) && VacuumHorizonHook)
+	{
+		TransactionId horizon = VacuumHorizonHook();
+
+		if (TransactionIdIsValid(horizon) &&
+			TransactionIdFollows(xid, horizon))
+			return;
+	}
 
 	tuple->t_infomask |= infomask;
 	MarkBufferDirtyHint(buffer, true);
@@ -1794,9 +1798,3 @@ HeapTupleSatisfiesVisibility(HeapTuple htup, Snapshot snapshot, Buffer buffer)
 
 	return false;				/* keep compiler quiet */
 }
-
-void
-SetHintBitsHorizon(TransactionId new_horizon)
-{
-	hint_bit_horizon = new_horizon;
-}

src/backend/commands/vacuum.c

@@ -1119,6 +1119,14 @@ vacuum_get_cutoffs(Relation rel, const VacuumParams *params,
 	 * any time, and that each vacuum is always an independent transaction.
 	 */
 	cutoffs->OldestXmin = GetOldestNonRemovableTransactionId(rel);
+	if (VacuumHorizonHook)
+	{
+		TransactionId horizon = VacuumHorizonHook();
+
+		if (TransactionIdIsValid(horizon) &&
+			TransactionIdFollows(cutoffs->OldestXmin, horizon))
+			cutoffs->OldestXmin = horizon;
+	}
 
 	if (OldSnapshotThresholdActive())
 	{
@@ -1635,6 +1643,14 @@ vac_update_datfrozenxid(void)
 	 * cannot produce a wrong minimum by starting with this.
 	 */
 	newFrozenXid = GetOldestNonRemovableTransactionId(NULL);
+	if (VacuumHorizonHook)
+	{
+		TransactionId horizon = VacuumHorizonHook();
+
+		if (TransactionIdIsValid(horizon) &&
+			TransactionIdFollows(newFrozenXid, horizon))
+			newFrozenXid = horizon;
+	}
 
 	/*
 	 * Similarly, initialize the MultiXact "min" with the value that would be

src/include/access/heapam.h

@@ -314,6 +314,10 @@ extern void heap_vacuum_rel(Relation rel,
 							struct VacuumParams *params, BufferAccessStrategy bstrategy);
 
 /* in heap/heapam_visibility.c */
+typedef TransactionId (*VacuumHorizonHookType) (void);
+
+extern VacuumHorizonHookType VacuumHorizonHook;
+
 extern bool HeapTupleSatisfiesVisibility(HeapTuple htup, Snapshot snapshot,
 										 Buffer buffer);
 extern TM_Result HeapTupleSatisfiesUpdate(HeapTuple htup, CommandId curcid,
@@ -328,8 +332,6 @@ extern bool HeapTupleHeaderIsOnlyLocked(HeapTupleHeader tuple);
 extern bool HeapTupleIsSurelyDead(HeapTuple htup,
 								  struct GlobalVisState *vistest);
 
-extern void SetHintBitsHorizon(TransactionId new_horizon);
-
 /*
  * To avoid leaking too much knowledge about reorderbuffer implementation
  * details this is implemented in reorderbuffer.c not heapam_visibility.c