Modify BufferGetPage() to prepare for "snapshot too old" feature

This patch is a no-op patch which is intended to reduce the chances
of failures of omission once the functional part of the "snapshot
too old" patch goes in.  It adds parameters for snapshot, relation,
and an enum to specify whether the snapshot age check needs to be
done for the page at this point.  This initial patch passes NULL
for the first two new parameters and BGP_NO_SNAPSHOT_TEST for the
third.  The follow-on patch will change the places where the test
needs to be made.

6 files changed, 52 insertions, 34 deletions

diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 996363c2ded..999e71cafca 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -211,7 +211,8 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 				bool markfollowright)
 {
 	BlockNumber blkno = BufferGetBlockNumber(buffer);
-	Page		page = BufferGetPage(buffer);
+	Page		page = BufferGetPage(buffer, NULL, NULL,
+									 BGP_NO_SNAPSHOT_TEST);
 	bool		is_leaf = (GistPageIsLeaf(page)) ? true : false;
 	XLogRecPtr	recptr;
 	int			i;
@@ -316,7 +317,9 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 
 			dist->buffer = buffer;
 			dist->block.blkno = BufferGetBlockNumber(buffer);
-			dist->page = PageGetTempPageCopySpecial(BufferGetPage(buffer));
+			dist->page =
+				PageGetTempPageCopySpecial(BufferGetPage(buffer, NULL, NULL,
+														 BGP_NO_SNAPSHOT_TEST));
 
 			/* clean all flags except F_LEAF */
 			GistPageGetOpaque(dist->page)->flags = (is_leaf) ? F_LEAF : 0;
@@ -328,7 +331,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 			/* Allocate new page */
 			ptr->buffer = gistNewBuffer(rel);
 			GISTInitBuffer(ptr->buffer, (is_leaf) ? F_LEAF : 0);
-			ptr->page = BufferGetPage(ptr->buffer);
+			ptr->page = BufferGetPage(ptr->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 			ptr->block.blkno = BufferGetBlockNumber(ptr->buffer);
 		}
 
@@ -354,7 +357,10 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 			int			i;
 
 			rootpg.buffer = buffer;
-			rootpg.page = PageGetTempPageCopySpecial(BufferGetPage(rootpg.buffer));
+			rootpg.page =
+				PageGetTempPageCopySpecial(BufferGetPage(rootpg.buffer,
+														 NULL, NULL,
+														 BGP_NO_SNAPSHOT_TEST));
 			GistPageGetOpaque(rootpg.page)->flags = 0;
 
 			/* Prepare a vector of all the downlinks */
@@ -462,8 +468,11 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 		 * The first page in the chain was a temporary working copy meant to
 		 * replace the old page. Copy it over the old page.
 		 */
-		PageRestoreTempPage(dist->page, BufferGetPage(dist->buffer));
-		dist->page = BufferGetPage(dist->buffer);
+		PageRestoreTempPage(dist->page, BufferGetPage(dist->buffer,
+													  NULL, NULL,
+													  BGP_NO_SNAPSHOT_TEST));
+		dist->page = BufferGetPage(dist->buffer, NULL, NULL,
+								   BGP_NO_SNAPSHOT_TEST);
 
 		/* Write the WAL record */
 		if (RelationNeedsWAL(rel))
@@ -554,7 +563,8 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 	 */
 	if (BufferIsValid(leftchildbuf))
 	{
-		Page		leftpg = BufferGetPage(leftchildbuf);
+		Page		leftpg = BufferGetPage(leftchildbuf, NULL, NULL,
+										   BGP_NO_SNAPSHOT_TEST);
 
 		GistPageSetNSN(leftpg, recptr);
 		GistClearFollowRight(leftpg);
@@ -614,7 +624,8 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace, GISTSTATE *giststate)
 			gistcheckpage(state.r, stack->buffer);
 		}
 
-		stack->page = (Page) BufferGetPage(stack->buffer);
+		stack->page = BufferGetPage(stack->buffer, NULL, NULL,
+									BGP_NO_SNAPSHOT_TEST);
 		stack->lsn = PageGetLSN(stack->page);
 		Assert(!RelationNeedsWAL(state.r) || !XLogRecPtrIsInvalid(stack->lsn));
 
@@ -699,7 +710,8 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace, GISTSTATE *giststate)
 					LockBuffer(stack->buffer, GIST_UNLOCK);
 					LockBuffer(stack->buffer, GIST_EXCLUSIVE);
 					xlocked = true;
-					stack->page = (Page) BufferGetPage(stack->buffer);
+					stack->page = BufferGetPage(stack->buffer, NULL, NULL,
+												BGP_NO_SNAPSHOT_TEST);
 
 					if (PageGetLSN(stack->page) != stack->lsn)
 					{
@@ -763,7 +775,8 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace, GISTSTATE *giststate)
 				LockBuffer(stack->buffer, GIST_UNLOCK);
 				LockBuffer(stack->buffer, GIST_EXCLUSIVE);
 				xlocked = true;
-				stack->page = (Page) BufferGetPage(stack->buffer);
+				stack->page = BufferGetPage(stack->buffer, NULL, NULL,
+											BGP_NO_SNAPSHOT_TEST);
 				stack->lsn = PageGetLSN(stack->page);
 
 				if (stack->blkno == GIST_ROOT_BLKNO)
@@ -853,7 +866,7 @@ gistFindPath(Relation r, BlockNumber child, OffsetNumber *downlinkoffnum)
 		buffer = ReadBuffer(r, top->blkno);
 		LockBuffer(buffer, GIST_SHARE);
 		gistcheckpage(r, buffer);
-		page = (Page) BufferGetPage(buffer);
+		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 		if (GistPageIsLeaf(page))
 		{
@@ -941,7 +954,8 @@ gistFindCorrectParent(Relation r, GISTInsertStack *child)
 	GISTInsertStack *parent = child->parent;
 
 	gistcheckpage(r, parent->buffer);
-	parent->page = (Page) BufferGetPage(parent->buffer);
+	parent->page = BufferGetPage(parent->buffer, NULL, NULL,
+								 BGP_NO_SNAPSHOT_TEST);
 
 	/* here we don't need to distinguish between split and page update */
 	if (child->downlinkoffnum == InvalidOffsetNumber ||
@@ -982,7 +996,8 @@ gistFindCorrectParent(Relation r, GISTInsertStack *child)
 			parent->buffer = ReadBuffer(r, parent->blkno);
 			LockBuffer(parent->buffer, GIST_EXCLUSIVE);
 			gistcheckpage(r, parent->buffer);
-			parent->page = (Page) BufferGetPage(parent->buffer);
+			parent->page = BufferGetPage(parent->buffer, NULL, NULL,
+										 BGP_NO_SNAPSHOT_TEST);
 		}
 
 		/*
@@ -1006,7 +1021,8 @@ gistFindCorrectParent(Relation r, GISTInsertStack *child)
 		while (ptr)
 		{
 			ptr->buffer = ReadBuffer(r, ptr->blkno);
-			ptr->page = (Page) BufferGetPage(ptr->buffer);
+			ptr->page = BufferGetPage(ptr->buffer, NULL, NULL,
+									  BGP_NO_SNAPSHOT_TEST);
 			ptr = ptr->parent;
 		}
 
@@ -1028,7 +1044,7 @@ static IndexTuple
 gistformdownlink(Relation rel, Buffer buf, GISTSTATE *giststate,
 				 GISTInsertStack *stack)
 {
-	Page		page = BufferGetPage(buf);
+	Page		page = BufferGetPage(buf, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 	OffsetNumber maxoff;
 	OffsetNumber offset;
 	IndexTuple	downlink = NULL;
@@ -1109,7 +1125,7 @@ gistfixsplit(GISTInsertState *state, GISTSTATE *giststate)
 		GISTPageSplitInfo *si = palloc(sizeof(GISTPageSplitInfo));
 		IndexTuple	downlink;
 
-		page = BufferGetPage(buf);
+		page = BufferGetPage(buf, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 		/* Form the new downlink tuples to insert to parent */
 		downlink = gistformdownlink(state->r, buf, giststate, stack);
diff --git a/src/backend/access/gist/gistbuild.c b/src/backend/access/gist/gistbuild.c
index 4e43a6932a4..8e7389c05f3 100644
--- a/src/backend/access/gist/gistbuild.c
+++ b/src/backend/access/gist/gistbuild.c
@@ -169,7 +169,7 @@ gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	/* initialize the root page */
 	buffer = gistNewBuffer(index);
 	Assert(BufferGetBlockNumber(buffer) == GIST_ROOT_BLKNO);
-	page = BufferGetPage(buffer);
+	page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 	START_CRIT_SECTION();
 
@@ -589,7 +589,7 @@ gistProcessItup(GISTBuildState *buildstate, IndexTuple itup,
 		buffer = ReadBuffer(indexrel, blkno);
 		LockBuffer(buffer, GIST_EXCLUSIVE);
 
-		page = (Page) BufferGetPage(buffer);
+		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 		childoffnum = gistchoose(indexrel, page, itup, giststate);
 		iid = PageGetItemId(page, childoffnum);
 		idxtuple = (IndexTuple) PageGetItem(page, iid);
@@ -699,7 +699,8 @@ gistbufferinginserttuples(GISTBuildState *buildstate, Buffer buffer, int level,
 	 */
 	if (is_split && BufferGetBlockNumber(buffer) == GIST_ROOT_BLKNO)
 	{
-		Page		page = BufferGetPage(buffer);
+		Page		page = BufferGetPage(buffer, NULL, NULL,
+										 BGP_NO_SNAPSHOT_TEST);
 		OffsetNumber off;
 		OffsetNumber maxoff;
 
@@ -866,7 +867,7 @@ gistBufferingFindCorrectParent(GISTBuildState *buildstate,
 	}
 
 	buffer = ReadBuffer(buildstate->indexrel, parent);
-	page = BufferGetPage(buffer);
+	page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 	LockBuffer(buffer, GIST_EXCLUSIVE);
 	gistcheckpage(buildstate->indexrel, buffer);
 	maxoff = PageGetMaxOffsetNumber(page);
@@ -1067,7 +1068,7 @@ gistGetMaxLevel(Relation index)
 		 * pro forma.
 		 */
 		LockBuffer(buffer, GIST_SHARE);
-		page = (Page) BufferGetPage(buffer);
+		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 		if (GistPageIsLeaf(page))
 		{
@@ -1167,7 +1168,8 @@ gistMemorizeAllDownlinks(GISTBuildState *buildstate, Buffer parentbuf)
 	OffsetNumber maxoff;
 	OffsetNumber off;
 	BlockNumber parentblkno = BufferGetBlockNumber(parentbuf);
-	Page		page = BufferGetPage(parentbuf);
+	Page		page = BufferGetPage(parentbuf, NULL, NULL,
+									 BGP_NO_SNAPSHOT_TEST);
 
 	Assert(!GistPageIsLeaf(page));
 
diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
index 81383835c88..13a039947ba 100644
--- a/src/backend/access/gist/gistget.c
+++ b/src/backend/access/gist/gistget.c
@@ -54,7 +54,7 @@ gistkillitems(IndexScanDesc scan)
 
 	LockBuffer(buffer, GIST_SHARE);
 	gistcheckpage(scan->indexRelation, buffer);
-	page = BufferGetPage(buffer);
+	page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 	/*
 	 * If page LSN differs it means that the page was modified since the last read.
@@ -336,7 +336,7 @@ gistScanPage(IndexScanDesc scan, GISTSearchItem *pageItem, double *myDistances,
 	buffer = ReadBuffer(scan->indexRelation, pageItem->blkno);
 	LockBuffer(buffer, GIST_SHARE);
 	gistcheckpage(scan->indexRelation, buffer);
-	page = BufferGetPage(buffer);
+	page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 	opaque = GistPageGetOpaque(page);
 
 	/*
diff --git a/src/backend/access/gist/gistutil.c b/src/backend/access/gist/gistutil.c
index fac166d4c29..5d16cf51e8f 100644
--- a/src/backend/access/gist/gistutil.c
+++ b/src/backend/access/gist/gistutil.c
@@ -701,7 +701,7 @@ GISTInitBuffer(Buffer b, uint32 f)
 	Size		pageSize;
 
 	pageSize = BufferGetPageSize(b);
-	page = BufferGetPage(b);
+	page = BufferGetPage(b, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 	PageInit(page, pageSize, sizeof(GISTPageOpaqueData));
 
 	opaque = GistPageGetOpaque(page);
@@ -718,7 +718,7 @@ GISTInitBuffer(Buffer b, uint32 f)
 void
 gistcheckpage(Relation rel, Buffer buf)
 {
-	Page		page = BufferGetPage(buf);
+	Page		page = BufferGetPage(buf, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 	/*
 	 * ReadBuffer verifies that every newly-read page passes
@@ -776,7 +776,7 @@ gistNewBuffer(Relation r)
 		 */
 		if (ConditionalLockBuffer(buffer))
 		{
-			Page		page = BufferGetPage(buffer);
+			Page		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 			if (PageIsNew(page))
 				return buffer;	/* OK to use, if never initialized */
diff --git a/src/backend/access/gist/gistvacuum.c b/src/backend/access/gist/gistvacuum.c
index 7947ff9dbe6..9d9f5dcf41c 100644
--- a/src/backend/access/gist/gistvacuum.c
+++ b/src/backend/access/gist/gistvacuum.c
@@ -75,7 +75,7 @@ gistvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
 		buffer = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL,
 									info->strategy);
 		LockBuffer(buffer, GIST_SHARE);
-		page = (Page) BufferGetPage(buffer);
+		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 		if (PageIsNew(page) || GistPageIsDeleted(page))
 		{
@@ -166,7 +166,7 @@ gistbulkdelete(IndexVacuumInfo *info, IndexBulkDeleteResult *stats,
 									RBM_NORMAL, info->strategy);
 		LockBuffer(buffer, GIST_SHARE);
 		gistcheckpage(rel, buffer);
-		page = (Page) BufferGetPage(buffer);
+		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 		if (GistPageIsLeaf(page))
 		{
@@ -176,7 +176,7 @@ gistbulkdelete(IndexVacuumInfo *info, IndexBulkDeleteResult *stats,
 			LockBuffer(buffer, GIST_UNLOCK);
 			LockBuffer(buffer, GIST_EXCLUSIVE);
 
-			page = (Page) BufferGetPage(buffer);
+			page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 			if (stack->blkno == GIST_ROOT_BLKNO && !GistPageIsLeaf(page))
 			{
 				/* only the root can become non-leaf during relock */
diff --git a/src/backend/access/gist/gistxlog.c b/src/backend/access/gist/gistxlog.c
index b48e97cc66e..8ef6e98e7d4 100644
--- a/src/backend/access/gist/gistxlog.c
+++ b/src/backend/access/gist/gistxlog.c
@@ -46,7 +46,7 @@ gistRedoClearFollowRight(XLogReaderState *record, uint8 block_id)
 	action = XLogReadBufferForRedo(record, block_id, &buffer);
 	if (action == BLK_NEEDS_REDO || action == BLK_RESTORED)
 	{
-		page = BufferGetPage(buffer);
+		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 		GistPageSetNSN(page, lsn);
 		GistClearFollowRight(page);
@@ -78,7 +78,7 @@ gistRedoPageUpdateRecord(XLogReaderState *record)
 
 		data = begin = XLogRecGetBlockData(record, 0, &datalen);
 
-		page = (Page) BufferGetPage(buffer);
+		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 		/* Delete old tuples */
 		if (xldata->ntodelete > 0)
@@ -199,7 +199,7 @@ gistRedoPageSplitRecord(XLogReaderState *record)
 		}
 
 		buffer = XLogInitBufferForRedo(record, i + 1);
-		page = (Page) BufferGetPage(buffer);
+		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 		data = XLogRecGetBlockData(record, i + 1, &datalen);
 
 		tuples = decodePageSplitRecord(data, datalen, &num);
@@ -265,7 +265,7 @@ gistRedoCreateIndex(XLogReaderState *record)
 
 	buffer = XLogInitBufferForRedo(record, 0);
 	Assert(BufferGetBlockNumber(buffer) == GIST_ROOT_BLKNO);
-	page = (Page) BufferGetPage(buffer);
+	page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 	GISTInitBuffer(buffer, F_LEAF);