Revert no-op changes to BufferGetPage()

The reverted changes were intended to force a choice of whether any
newly-added BufferGetPage() calls needed to be accompanied by a
test of the snapshot age, to support the "snapshot too old"
feature.  Such an accompanying test is needed in about 7% of the
cases, where the page is being used as part of a scan rather than
positioning for other purposes (such as DML or vacuuming).  The
additional effort required for back-patching, and the doubt whether
the intended benefit would really be there, have indicated it is
best just to rely on developers to do the right thing based on
comments and existing usage, as we do with many other conventions.

This change should have little or no effect on generated executable
code.

Motivated by the back-patching pain of Tom Lane and Robert Haas

1 files changed, 21 insertions, 20 deletions

diff --git a/src/backend/access/gin/ginget.c b/src/backend/access/gin/ginget.c
index 610829852a6..9ed9fd2dc56 100644
--- a/src/backend/access/gin/ginget.c
+++ b/src/backend/access/gin/ginget.c
@@ -19,7 +19,6 @@
 #include "miscadmin.h"
 #include "utils/datum.h"
 #include "utils/memutils.h"
-#include "utils/rel.h"
 
 /* GUC parameter */
 int			GinFuzzySearchLimit = 0;
@@ -40,8 +39,7 @@ typedef struct pendingPosition
 static bool
 moveRightIfItNeeded(GinBtreeData *btree, GinBtreeStack *stack)
 {
-	Page		page = BufferGetPage(stack->buffer, NULL, NULL,
-									 BGP_NO_SNAPSHOT_TEST);
+	Page		page = BufferGetPage(stack->buffer);
 
 	if (stack->off > PageGetMaxOffsetNumber(page))
 	{
@@ -84,7 +82,7 @@ scanPostingTree(Relation index, GinScanEntry scanEntry,
 	 */
 	for (;;)
 	{
-		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
+		page = BufferGetPage(buffer);
 		if ((GinPageGetOpaque(page)->flags & GIN_DELETED) == 0)
 		{
 			int			n = GinDataLeafPageGetItemsToTbm(page, scanEntry->matchBitmap);
@@ -146,8 +144,8 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
 		if (moveRightIfItNeeded(btree, stack) == false)
 			return true;
 
-		page = BufferGetPage(stack->buffer, snapshot, btree->index,
-							 BGP_TEST_FOR_OLD_SNAPSHOT);
+		page = BufferGetPage(stack->buffer);
+		TestForOldSnapshot(snapshot, btree->index, page);
 		itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stack->off));
 
 		/*
@@ -227,14 +225,15 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
 			LockBuffer(stack->buffer, GIN_UNLOCK);
 
 			/* Collect all the TIDs in this entry's posting tree */
-			scanPostingTree(btree->index, scanEntry, rootPostingTree, snapshot);
+			scanPostingTree(btree->index, scanEntry, rootPostingTree,
+							snapshot);
 
 			/*
 			 * We lock again the entry page and while it was unlocked insert
 			 * might have occurred, so we need to re-find our position.
 			 */
 			LockBuffer(stack->buffer, GIN_SHARE);
-			page = BufferGetPage(stack->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
+			page = BufferGetPage(stack->buffer);
 			if (!GinPageIsLeaf(page))
 			{
 				/*
@@ -254,7 +253,7 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
 				if (moveRightIfItNeeded(btree, stack) == false)
 					elog(ERROR, "lost saved point in index");	/* must not happen !!! */
 
-				page = BufferGetPage(stack->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
+				page = BufferGetPage(stack->buffer);
 				itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stack->off));
 
 				if (gintuple_get_attrnum(btree->ginstate, itup) != attnum)
@@ -323,7 +322,8 @@ restartScanEntry:
 						entry->queryKey, entry->queryCategory,
 						ginstate);
 	stackEntry = ginFindLeafPage(&btreeEntry, true, snapshot);
-	page = BufferGetPage(stackEntry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
+	page = BufferGetPage(stackEntry->buffer);
+	/* ginFindLeafPage() will have already checked snapshot age. */
 	needUnlock = TRUE;
 
 	entry->isFinished = TRUE;
@@ -339,7 +339,8 @@ restartScanEntry:
 		 * for the entry type.
 		 */
 		btreeEntry.findItem(&btreeEntry, stackEntry);
-		if (!collectMatchBitmap(&btreeEntry, stackEntry, entry, snapshot))
+		if (collectMatchBitmap(&btreeEntry, stackEntry, entry, snapshot)
+			== false)
 		{
 			/*
 			 * GIN tree was seriously restructured, so we will cleanup all
@@ -397,7 +398,7 @@ restartScanEntry:
 			 */
 			IncrBufferRefCount(entry->buffer);
 
-			page = BufferGetPage(entry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
+			page = BufferGetPage(entry->buffer);
 
 			/*
 			 * Load the first page into memory.
@@ -643,7 +644,7 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry,
 		 GinItemPointerGetOffsetNumber(&advancePast),
 		 !stepright);
 
-	page = BufferGetPage(entry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
+	page = BufferGetPage(entry->buffer);
 	for (;;)
 	{
 		entry->offset = InvalidOffsetNumber;
@@ -675,7 +676,7 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry,
 			entry->buffer = ginStepRight(entry->buffer,
 										 ginstate->index,
 										 GIN_SHARE);
-			page = BufferGetPage(entry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
+			page = BufferGetPage(entry->buffer);
 		}
 		stepright = true;
 
@@ -1337,8 +1338,8 @@ scanGetCandidate(IndexScanDesc scan, pendingPosition *pos)
 	ItemPointerSetInvalid(&pos->item);
 	for (;;)
 	{
-		page = BufferGetPage(pos->pendingBuffer, scan->xs_snapshot,
-							 scan->indexRelation, BGP_TEST_FOR_OLD_SNAPSHOT);
+		page = BufferGetPage(pos->pendingBuffer);
+		TestForOldSnapshot(scan->xs_snapshot, scan->indexRelation, page);
 
 		maxoff = PageGetMaxOffsetNumber(page);
 		if (pos->firstOffset > maxoff)
@@ -1518,8 +1519,8 @@ collectMatchesForHeapRow(IndexScanDesc scan, pendingPosition *pos)
 		memset(datumExtracted + pos->firstOffset - 1, 0,
 			   sizeof(bool) * (pos->lastOffset - pos->firstOffset));
 
-		page = BufferGetPage(pos->pendingBuffer, scan->xs_snapshot,
-							 scan->indexRelation, BGP_TEST_FOR_OLD_SNAPSHOT);
+		page = BufferGetPage(pos->pendingBuffer);
+		TestForOldSnapshot(scan->xs_snapshot, scan->indexRelation, page);
 
 		for (i = 0; i < so->nkeys; i++)
 		{
@@ -1712,8 +1713,8 @@ scanPendingInsert(IndexScanDesc scan, TIDBitmap *tbm, int64 *ntids)
 	*ntids = 0;
 
 	LockBuffer(metabuffer, GIN_SHARE);
-	page = BufferGetPage(metabuffer, scan->xs_snapshot, scan->indexRelation,
-						 BGP_TEST_FOR_OLD_SNAPSHOT);
+	page = BufferGetPage(metabuffer);
+	TestForOldSnapshot(scan->xs_snapshot, scan->indexRelation, page);
 	blkno = GinPageGetMeta(page)->head;
 
 	/*