Return data from heap_page_prune via a struct.

Previously, one of the values in the struct was returned as the return
value, and another was returned via an output parameter. In
preparation for returning more stuff, consolidate both values into a
struct returned via an output parameter.

Melanie Plageman, reviewed by Andres Freund and by me.

Discussion: https://postgr.es/m/CAAKRu_br124qsGJieuYA0nGjywEukhK1dKBfRdby_4yY3E9SXA%40mail.gmail.com

1 files changed, 15 insertions, 18 deletions

diff --git a/src/backend/access/heap/pruneheap.c b/src/backend/access/heap/pruneheap.c
index 18193efa238..d5892a2db46 100644
--- a/src/backend/access/heap/pruneheap.c
+++ b/src/backend/access/heap/pruneheap.c
@@ -155,15 +155,13 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
 		 */
 		if (PageIsFull(page) || PageGetHeapFreeSpace(page) < minfree)
 		{
-			int			ndeleted,
-						nnewlpdead;
+			PruneResult presult;
 
-			ndeleted = heap_page_prune(relation, buffer, vistest,
-									   &nnewlpdead, NULL);
+			heap_page_prune(relation, buffer, vistest, &presult, NULL);
 
 			/*
 			 * Report the number of tuples reclaimed to pgstats.  This is
-			 * ndeleted minus the number of newly-LP_DEAD-set items.
+			 * presult.ndeleted minus the number of newly-LP_DEAD-set items.
 			 *
 			 * We derive the number of dead tuples like this to avoid totally
 			 * forgetting about items that were set to LP_DEAD, since they
@@ -175,9 +173,9 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
 			 * tracks ndeleted, since it will set the same LP_DEAD items to
 			 * LP_UNUSED separately.
 			 */
-			if (ndeleted > nnewlpdead)
+			if (presult.ndeleted > presult.nnewlpdead)
 				pgstat_update_heap_dead_tuples(relation,
-											   ndeleted - nnewlpdead);
+											   presult.ndeleted - presult.nnewlpdead);
 		}
 
 		/* And release buffer lock */
@@ -204,21 +202,19 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
  * (see heap_prune_satisfies_vacuum and
  * HeapTupleSatisfiesVacuum).
  *
- * Sets *nnewlpdead for caller, indicating the number of items that were
- * newly set LP_DEAD during prune operation.
- *
  * off_loc is the offset location required by the caller to use in error
  * callback.
  *
- * Returns the number of tuples deleted from the page during this call.
+ * presult contains output parameters needed by callers such as the number of
+ * tuples removed and the number of line pointers newly marked LP_DEAD.
+ * heap_page_prune() is responsible for initializing it.
  */
-int
+void
 heap_page_prune(Relation relation, Buffer buffer,
 				GlobalVisState *vistest,
-				int *nnewlpdead,
+				PruneResult *presult,
 				OffsetNumber *off_loc)
 {
-	int			ndeleted = 0;
 	Page		page = BufferGetPage(buffer);
 	BlockNumber blockno = BufferGetBlockNumber(buffer);
 	OffsetNumber offnum,
@@ -244,6 +240,9 @@ heap_page_prune(Relation relation, Buffer buffer,
 	prstate.nredirected = prstate.ndead = prstate.nunused = 0;
 	memset(prstate.marked, 0, sizeof(prstate.marked));
 
+	presult->ndeleted = 0;
+	presult->nnewlpdead = 0;
+
 	maxoff = PageGetMaxOffsetNumber(page);
 	tup.t_tableOid = RelationGetRelid(prstate.rel);
 
@@ -318,7 +317,7 @@ heap_page_prune(Relation relation, Buffer buffer,
 			continue;
 
 		/* Process this item or chain of items */
-		ndeleted += heap_prune_chain(buffer, offnum, &prstate);
+		presult->ndeleted += heap_prune_chain(buffer, offnum, &prstate);
 	}
 
 	/* Clear the offset information once we have processed the given page. */
@@ -419,9 +418,7 @@ heap_page_prune(Relation relation, Buffer buffer,
 	END_CRIT_SECTION();
 
 	/* Record number of newly-set-LP_DEAD items for caller */
-	*nnewlpdead = prstate.ndead;
-
-	return ndeleted;
+	presult->nnewlpdead = prstate.ndead;
 }