Introduce 'options' argument to heap_page_prune()

Currently there is only one option, HEAP_PAGE_PRUNE_MARK_UNUSED_NOW
which replaces the old boolean argument, but upcoming patches will
introduce at least one more. Having a lot of boolean arguments makes
it hard to see at the call sites what the arguments mean, so prefer a
bitmask of options with human-readable names.

Author: Melanie Plageman <melanieplageman@gmail.com>
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Discussion: https://www.postgresql.org/message-id/20240401172219.fngjosaqdgqqvg4e@liskov

src/backend/access/heap/pruneheap.c

@@ -166,7 +166,7 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
 			 * not the relation has indexes, since we cannot safely determine
 			 * that during on-access pruning with the current implementation.
 			 */
-			heap_page_prune(relation, buffer, vistest, false,
+			heap_page_prune(relation, buffer, vistest, 0,
 							&presult, PRUNE_ON_ACCESS, &dummy_off_loc);
 
 			/*
@@ -211,8 +211,9 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
  * vistest is used to distinguish whether tuples are DEAD or RECENTLY_DEAD
  * (see heap_prune_satisfies_vacuum).
  *
- * mark_unused_now indicates whether or not dead items can be set LP_UNUSED
+ * options:
- * during pruning.
+ *   MARK_UNUSED_NOW indicates that dead items can be set LP_UNUSED during
+ *   pruning.
  *
  * presult contains output parameters needed by callers such as the number of
  * tuples removed and the number of line pointers newly marked LP_DEAD.
@@ -227,7 +228,7 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
 void
 heap_page_prune(Relation relation, Buffer buffer,
 				GlobalVisState *vistest,
-				bool mark_unused_now,
+				int options,
 				PruneResult *presult,
 				PruneReason reason,
 				OffsetNumber *off_loc)
@@ -252,7 +253,7 @@ heap_page_prune(Relation relation, Buffer buffer,
 	 */
 	prstate.new_prune_xid = InvalidTransactionId;
 	prstate.vistest = vistest;
-	prstate.mark_unused_now = mark_unused_now;
+	prstate.mark_unused_now = (options & HEAP_PAGE_PRUNE_MARK_UNUSED_NOW) != 0;
 	prstate.snapshotConflictHorizon = InvalidTransactionId;
 	prstate.nredirected = prstate.ndead = prstate.nunused = 0;
 	prstate.ndeleted = 0;

src/backend/access/heap/vacuumlazy.c

@@ -1425,6 +1425,7 @@ lazy_scan_prune(LVRelState *vacrel,
 	bool		all_visible,
 				all_frozen;
 	TransactionId visibility_cutoff_xid;
+	int			prune_options = 0;
 	int64		fpi_before = pgWalUsage.wal_fpi;
 	OffsetNumber deadoffsets[MaxHeapTuplesPerPage];
 	HeapTupleFreeze frozen[MaxHeapTuplesPerPage];
@@ -1458,10 +1459,12 @@ lazy_scan_prune(LVRelState *vacrel,
 	 * that were deleted from indexes.
 	 *
 	 * If the relation has no indexes, we can immediately mark would-be dead
-	 * items LP_UNUSED, so mark_unused_now should be true if no indexes and
+	 * items LP_UNUSED.
-	 * false otherwise.
 	 */
-	heap_page_prune(rel, buf, vacrel->vistest, vacrel->nindexes == 0,
+	prune_options = 0;
+	if (vacrel->nindexes == 0)
+		prune_options = HEAP_PAGE_PRUNE_MARK_UNUSED_NOW;
+	heap_page_prune(rel, buf, vacrel->vistest, prune_options,
 					&presult, PRUNE_VACUUM_SCAN, &vacrel->offnum);
 
 	/*

src/include/access/heapam.h

@@ -36,6 +36,9 @@
 #define HEAP_INSERT_NO_LOGICAL	TABLE_INSERT_NO_LOGICAL
 #define HEAP_INSERT_SPECULATIVE 0x0010
 
+/* "options" flag bits for heap_page_prune */
+#define HEAP_PAGE_PRUNE_MARK_UNUSED_NOW		(1 << 0)
+
 typedef struct BulkInsertStateData *BulkInsertState;
 struct TupleTableSlot;
 struct VacuumCutoffs;
@@ -331,7 +334,7 @@ struct GlobalVisState;
 extern void heap_page_prune_opt(Relation relation, Buffer buffer);
 extern void heap_page_prune(Relation relation, Buffer buffer,
 							struct GlobalVisState *vistest,
-							bool mark_unused_now,
+							int options,
 							PruneResult *presult,
 							PruneReason reason,
 							OffsetNumber *off_loc);