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.

1 files changed, 44 insertions, 24 deletions

diff --git a/src/backend/access/gin/ginbtree.c b/src/backend/access/gin/ginbtree.c
index 06ba9cb957f..13258cca0ea 100644
--- a/src/backend/access/gin/ginbtree.c
+++ b/src/backend/access/gin/ginbtree.c
@@ -36,7 +36,7 @@ ginTraverseLock(Buffer buffer, bool searchMode)
 	int			access = GIN_SHARE;
 
 	LockBuffer(buffer, GIN_SHARE);
-	page = BufferGetPage(buffer);
+	page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 	if (GinPageIsLeaf(page))
 	{
 		if (searchMode == FALSE)
@@ -89,7 +89,7 @@ ginFindLeafPage(GinBtree btree, bool searchMode)
 
 		stack->off = InvalidOffsetNumber;
 
-		page = BufferGetPage(stack->buffer);
+		page = BufferGetPage(stack->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 		access = ginTraverseLock(stack->buffer, searchMode);
 
@@ -115,7 +115,8 @@ ginFindLeafPage(GinBtree btree, bool searchMode)
 
 			stack->buffer = ginStepRight(stack->buffer, btree->index, access);
 			stack->blkno = rightlink;
-			page = BufferGetPage(stack->buffer);
+			page = BufferGetPage(stack->buffer, NULL, NULL,
+								 BGP_NO_SNAPSHOT_TEST);
 
 			if (!searchMode && GinPageIsIncompleteSplit(page))
 				ginFinishSplit(btree, stack, false, NULL);
@@ -161,7 +162,7 @@ Buffer
 ginStepRight(Buffer buffer, Relation index, int lockmode)
 {
 	Buffer		nextbuffer;
-	Page		page = BufferGetPage(buffer);
+	Page		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 	bool		isLeaf = GinPageIsLeaf(page);
 	bool		isData = GinPageIsData(page);
 	BlockNumber blkno = GinPageGetOpaque(page)->rightlink;
@@ -171,7 +172,7 @@ ginStepRight(Buffer buffer, Relation index, int lockmode)
 	UnlockReleaseBuffer(buffer);
 
 	/* Sanity check that the page we stepped to is of similar kind. */
-	page = BufferGetPage(nextbuffer);
+	page = BufferGetPage(nextbuffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 	if (isLeaf != GinPageIsLeaf(page) || isData != GinPageIsData(page))
 		elog(ERROR, "right sibling of GIN page is of different type");
 
@@ -243,7 +244,7 @@ ginFindParents(GinBtree btree, GinBtreeStack *stack)
 	for (;;)
 	{
 		LockBuffer(buffer, GIN_EXCLUSIVE);
-		page = BufferGetPage(buffer);
+		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 		if (GinPageIsLeaf(page))
 			elog(ERROR, "Lost path");
 
@@ -274,7 +275,7 @@ ginFindParents(GinBtree btree, GinBtreeStack *stack)
 				break;
 			}
 			buffer = ginStepRight(buffer, btree->index, GIN_EXCLUSIVE);
-			page = BufferGetPage(buffer);
+			page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 			/* finish any incomplete splits, as above */
 			if (GinPageIsIncompleteSplit(page))
@@ -325,7 +326,8 @@ ginPlaceToPage(GinBtree btree, GinBtreeStack *stack,
 			   void *insertdata, BlockNumber updateblkno,
 			   Buffer childbuf, GinStatsData *buildStats)
 {
-	Page		page = BufferGetPage(stack->buffer);
+	Page		page = BufferGetPage(stack->buffer, NULL, NULL,
+									 BGP_NO_SNAPSHOT_TEST);
 	GinPlaceToPageRC rc;
 	uint16		xlflags = 0;
 	Page		childpage = NULL;
@@ -344,7 +346,7 @@ ginPlaceToPage(GinBtree btree, GinBtreeStack *stack,
 	{
 		Assert(BufferIsValid(childbuf));
 		Assert(updateblkno != InvalidBlockNumber);
-		childpage = BufferGetPage(childbuf);
+		childpage = BufferGetPage(childbuf, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 	}
 
 	/*
@@ -456,7 +458,8 @@ ginPlaceToPage(GinBtree btree, GinBtreeStack *stack,
 		data.flags = xlflags;
 		if (childbuf != InvalidBuffer)
 		{
-			Page		childpage = BufferGetPage(childbuf);
+			Page		childpage = BufferGetPage(childbuf, NULL, NULL,
+												  BGP_NO_SNAPSHOT_TEST);
 
 			GinPageGetOpaque(childpage)->flags &= ~GIN_INCOMPLETE_SPLIT;
 
@@ -538,14 +541,21 @@ ginPlaceToPage(GinBtree btree, GinBtreeStack *stack,
 		if (stack->parent == NULL)
 		{
 			MarkBufferDirty(lbuffer);
-			memcpy(BufferGetPage(stack->buffer), newrootpg, BLCKSZ);
-			memcpy(BufferGetPage(lbuffer), newlpage, BLCKSZ);
-			memcpy(BufferGetPage(rbuffer), newrpage, BLCKSZ);
+			memcpy(BufferGetPage(stack->buffer, NULL, NULL,
+								 BGP_NO_SNAPSHOT_TEST),
+				   newrootpg, BLCKSZ);
+			memcpy(BufferGetPage(lbuffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST),
+				   newlpage, BLCKSZ);
+			memcpy(BufferGetPage(rbuffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST),
+				   newrpage, BLCKSZ);
 		}
 		else
 		{
-			memcpy(BufferGetPage(stack->buffer), newlpage, BLCKSZ);
-			memcpy(BufferGetPage(rbuffer), newrpage, BLCKSZ);
+			memcpy(BufferGetPage(stack->buffer, NULL, NULL,
+								 BGP_NO_SNAPSHOT_TEST),
+				   newlpage, BLCKSZ);
+			memcpy(BufferGetPage(rbuffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST),
+				   newrpage, BLCKSZ);
 		}
 
 		/* write WAL record */
@@ -577,10 +587,16 @@ ginPlaceToPage(GinBtree btree, GinBtreeStack *stack,
 			XLogRegisterData((char *) &data, sizeof(ginxlogSplit));
 
 			recptr = XLogInsert(RM_GIN_ID, XLOG_GIN_SPLIT);
-			PageSetLSN(BufferGetPage(stack->buffer), recptr);
-			PageSetLSN(BufferGetPage(rbuffer), recptr);
+			PageSetLSN(BufferGetPage(stack->buffer, NULL, NULL,
+									 BGP_NO_SNAPSHOT_TEST),
+					   recptr);
+			PageSetLSN(BufferGetPage(rbuffer, NULL, NULL,
+									 BGP_NO_SNAPSHOT_TEST),
+					   recptr);
 			if (stack->parent == NULL)
-				PageSetLSN(BufferGetPage(lbuffer), recptr);
+				PageSetLSN(BufferGetPage(lbuffer, NULL, NULL,
+										 BGP_NO_SNAPSHOT_TEST),
+						   recptr);
 			if (BufferIsValid(childbuf))
 				PageSetLSN(childpage, recptr);
 		}
@@ -662,11 +678,12 @@ ginFinishSplit(GinBtree btree, GinBtreeStack *stack, bool freestack,
 		 * page that has no downlink in the parent, and splitting it further
 		 * would fail.
 		 */
-		if (GinPageIsIncompleteSplit(BufferGetPage(parent->buffer)))
+		if (GinPageIsIncompleteSplit(BufferGetPage(parent->buffer, NULL, NULL,
+												   BGP_NO_SNAPSHOT_TEST)))
 			ginFinishSplit(btree, parent, false, buildStats);
 
 		/* move right if it's needed */
-		page = BufferGetPage(parent->buffer);
+		page = BufferGetPage(parent->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 		while ((parent->off = btree->findChildPtr(btree, page, stack->blkno, parent->off)) == InvalidOffsetNumber)
 		{
 			if (GinPageRightMost(page))
@@ -684,15 +701,17 @@ ginFinishSplit(GinBtree btree, GinBtreeStack *stack, bool freestack,
 
 			parent->buffer = ginStepRight(parent->buffer, btree->index, GIN_EXCLUSIVE);
 			parent->blkno = BufferGetBlockNumber(parent->buffer);
-			page = BufferGetPage(parent->buffer);
+			page = BufferGetPage(parent->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
-			if (GinPageIsIncompleteSplit(BufferGetPage(parent->buffer)))
+			if (GinPageIsIncompleteSplit(BufferGetPage(parent->buffer, NULL, NULL,
+													   BGP_NO_SNAPSHOT_TEST)))
 				ginFinishSplit(btree, parent, false, buildStats);
 		}
 
 		/* insert the downlink */
 		insertdata = btree->prepareDownlink(btree, stack->buffer);
-		updateblkno = GinPageGetOpaque(BufferGetPage(stack->buffer))->rightlink;
+		updateblkno = GinPageGetOpaque(BufferGetPage(stack->buffer, NULL, NULL,
+													 BGP_NO_SNAPSHOT_TEST))->rightlink;
 		done = ginPlaceToPage(btree, parent,
 							  insertdata, updateblkno,
 							  stack->buffer, buildStats);
@@ -742,7 +761,8 @@ ginInsertValue(GinBtree btree, GinBtreeStack *stack, void *insertdata,
 	bool		done;
 
 	/* If the leaf page was incompletely split, finish the split first */
-	if (GinPageIsIncompleteSplit(BufferGetPage(stack->buffer)))
+	if (GinPageIsIncompleteSplit(BufferGetPage(stack->buffer, NULL, NULL,
+											   BGP_NO_SNAPSHOT_TEST)))
 		ginFinishSplit(btree, stack, false, buildStats);
 
 	done = ginPlaceToPage(btree, stack,