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, 32 insertions, 16 deletions

diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 996363c2de..999e71cafc 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);