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, 33 insertions, 25 deletions

diff --git a/src/backend/access/gin/ginget.c b/src/backend/access/gin/ginget.c
index 53290a4279b..33683278e10 100644
--- a/src/backend/access/gin/ginget.c
+++ b/src/backend/access/gin/ginget.c
@@ -19,6 +19,7 @@
 #include "miscadmin.h"
 #include "utils/datum.h"
 #include "utils/memutils.h"
+#include "utils/rel.h"
 
 /* GUC parameter */
 int			GinFuzzySearchLimit = 0;
@@ -39,7 +40,8 @@ typedef struct pendingPosition
 static bool
 moveRightIfItNeeded(GinBtreeData *btree, GinBtreeStack *stack)
 {
-	Page		page = BufferGetPage(stack->buffer);
+	Page		page = BufferGetPage(stack->buffer, NULL, NULL,
+									 BGP_NO_SNAPSHOT_TEST);
 
 	if (stack->off > PageGetMaxOffsetNumber(page))
 	{
@@ -63,7 +65,7 @@ moveRightIfItNeeded(GinBtreeData *btree, GinBtreeStack *stack)
  */
 static void
 scanPostingTree(Relation index, GinScanEntry scanEntry,
-				BlockNumber rootPostingTree)
+				BlockNumber rootPostingTree, Snapshot snapshot)
 {
 	GinBtreeData btree;
 	GinBtreeStack *stack;
@@ -82,7 +84,7 @@ scanPostingTree(Relation index, GinScanEntry scanEntry,
 	 */
 	for (;;)
 	{
-		page = BufferGetPage(buffer);
+		page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 		if ((GinPageGetOpaque(page)->flags & GIN_DELETED) == 0)
 		{
 			int			n = GinDataLeafPageGetItemsToTbm(page, scanEntry->matchBitmap);
@@ -114,7 +116,7 @@ scanPostingTree(Relation index, GinScanEntry scanEntry,
  */
 static bool
 collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
-				   GinScanEntry scanEntry)
+				   GinScanEntry scanEntry, Snapshot snapshot)
 {
 	OffsetNumber attnum;
 	Form_pg_attribute attr;
@@ -144,7 +146,7 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
 		if (moveRightIfItNeeded(btree, stack) == false)
 			return true;
 
-		page = BufferGetPage(stack->buffer);
+		page = BufferGetPage(stack->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 		itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stack->off));
 
 		/*
@@ -224,14 +226,14 @@ 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);
+			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);
+			page = BufferGetPage(stack->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 			if (!GinPageIsLeaf(page))
 			{
 				/*
@@ -251,7 +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);
+				page = BufferGetPage(stack->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 				itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stack->off));
 
 				if (gintuple_get_attrnum(btree->ginstate, itup) != attnum)
@@ -291,7 +293,7 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
  * Start* functions setup beginning state of searches: finds correct buffer and pins it.
  */
 static void
-startScanEntry(GinState *ginstate, GinScanEntry entry)
+startScanEntry(GinState *ginstate, GinScanEntry entry, Snapshot snapshot)
 {
 	GinBtreeData btreeEntry;
 	GinBtreeStack *stackEntry;
@@ -319,7 +321,7 @@ restartScanEntry:
 						entry->queryKey, entry->queryCategory,
 						ginstate);
 	stackEntry = ginFindLeafPage(&btreeEntry, true);
-	page = BufferGetPage(stackEntry->buffer);
+	page = BufferGetPage(stackEntry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 	needUnlock = TRUE;
 
 	entry->isFinished = TRUE;
@@ -335,7 +337,7 @@ restartScanEntry:
 		 * for the entry type.
 		 */
 		btreeEntry.findItem(&btreeEntry, stackEntry);
-		if (collectMatchBitmap(&btreeEntry, stackEntry, entry) == false)
+		if (!collectMatchBitmap(&btreeEntry, stackEntry, entry, snapshot))
 		{
 			/*
 			 * GIN tree was seriously restructured, so we will cleanup all
@@ -393,7 +395,7 @@ restartScanEntry:
 			 */
 			IncrBufferRefCount(entry->buffer);
 
-			page = BufferGetPage(entry->buffer);
+			page = BufferGetPage(entry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 
 			/*
 			 * Load the first page into memory.
@@ -535,7 +537,7 @@ startScan(IndexScanDesc scan)
 	uint32		i;
 
 	for (i = 0; i < so->totalentries; i++)
-		startScanEntry(ginstate, so->entries[i]);
+		startScanEntry(ginstate, so->entries[i], scan->xs_snapshot);
 
 	if (GinFuzzySearchLimit > 0)
 	{
@@ -580,7 +582,8 @@ startScan(IndexScanDesc scan)
  * keep it pinned to prevent interference with vacuum.
  */
 static void
-entryLoadMoreItems(GinState *ginstate, GinScanEntry entry, ItemPointerData advancePast)
+entryLoadMoreItems(GinState *ginstate, GinScanEntry entry,
+				   ItemPointerData advancePast, Snapshot snapshot)
 {
 	Page		page;
 	int			i;
@@ -638,7 +641,7 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry, ItemPointerData advan
 		 GinItemPointerGetOffsetNumber(&advancePast),
 		 !stepright);
 
-	page = BufferGetPage(entry->buffer);
+	page = BufferGetPage(entry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 	for (;;)
 	{
 		entry->offset = InvalidOffsetNumber;
@@ -670,7 +673,7 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry, ItemPointerData advan
 			entry->buffer = ginStepRight(entry->buffer,
 										 ginstate->index,
 										 GIN_SHARE);
-			page = BufferGetPage(entry->buffer);
+			page = BufferGetPage(entry->buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
 		}
 		stepright = true;
 
@@ -734,7 +737,7 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry, ItemPointerData advan
  */
 static void
 entryGetItem(GinState *ginstate, GinScanEntry entry,
-			 ItemPointerData advancePast)
+			 ItemPointerData advancePast, Snapshot snapshot)
 {
 	Assert(!entry->isFinished);
 
@@ -857,7 +860,7 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
 			/* If we've processed the current batch, load more items */
 			while (entry->offset >= entry->nlist)
 			{
-				entryLoadMoreItems(ginstate, entry, advancePast);
+				entryLoadMoreItems(ginstate, entry, advancePast, snapshot);
 
 				if (entry->isFinished)
 				{
@@ -896,7 +899,7 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
  */
 static void
 keyGetItem(GinState *ginstate, MemoryContext tempCtx, GinScanKey key,
-		   ItemPointerData advancePast)
+		   ItemPointerData advancePast, Snapshot snapshot)
 {
 	ItemPointerData minItem;
 	ItemPointerData curPageLossy;
@@ -943,7 +946,7 @@ keyGetItem(GinState *ginstate, MemoryContext tempCtx, GinScanKey key,
 		 */
 		if (ginCompareItemPointers(&entry->curItem, &advancePast) <= 0)
 		{
-			entryGetItem(ginstate, entry, advancePast);
+			entryGetItem(ginstate, entry, advancePast, snapshot);
 			if (entry->isFinished)
 				continue;
 		}
@@ -1001,7 +1004,7 @@ keyGetItem(GinState *ginstate, MemoryContext tempCtx, GinScanKey key,
 
 		if (ginCompareItemPointers(&entry->curItem, &advancePast) <= 0)
 		{
-			entryGetItem(ginstate, entry, advancePast);
+			entryGetItem(ginstate, entry, advancePast, snapshot);
 			if (entry->isFinished)
 				continue;
 		}
@@ -1210,7 +1213,8 @@ scanGetItem(IndexScanDesc scan, ItemPointerData advancePast,
 			GinScanKey	key = so->keys + i;
 
 			/* Fetch the next item for this key that is > advancePast. */
-			keyGetItem(&so->ginstate, so->tempCtx, key, advancePast);
+			keyGetItem(&so->ginstate, so->tempCtx, key, advancePast,
+					   scan->xs_snapshot);
 
 			if (key->isFinished)
 				return false;
@@ -1331,7 +1335,8 @@ scanGetCandidate(IndexScanDesc scan, pendingPosition *pos)
 	ItemPointerSetInvalid(&pos->item);
 	for (;;)
 	{
-		page = BufferGetPage(pos->pendingBuffer);
+		page = BufferGetPage(pos->pendingBuffer, NULL,
+							 NULL, BGP_NO_SNAPSHOT_TEST);
 
 		maxoff = PageGetMaxOffsetNumber(page);
 		if (pos->firstOffset > maxoff)
@@ -1511,7 +1516,8 @@ collectMatchesForHeapRow(IndexScanDesc scan, pendingPosition *pos)
 		memset(datumExtracted + pos->firstOffset - 1, 0,
 			   sizeof(bool) * (pos->lastOffset - pos->firstOffset));
 
-		page = BufferGetPage(pos->pendingBuffer);
+		page = BufferGetPage(pos->pendingBuffer, NULL,
+							 NULL, BGP_NO_SNAPSHOT_TEST);
 
 		for (i = 0; i < so->nkeys; i++)
 		{
@@ -1698,12 +1704,14 @@ scanPendingInsert(IndexScanDesc scan, TIDBitmap *tbm, int64 *ntids)
 	int			i;
 	pendingPosition pos;
 	Buffer		metabuffer = ReadBuffer(scan->indexRelation, GIN_METAPAGE_BLKNO);
+	Page		page;
 	BlockNumber blkno;
 
 	*ntids = 0;
 
 	LockBuffer(metabuffer, GIN_SHARE);
-	blkno = GinPageGetMeta(BufferGetPage(metabuffer))->head;
+	page = BufferGetPage(metabuffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
+	blkno = GinPageGetMeta(page)->head;
 
 	/*
 	 * fetch head of list before unlocking metapage. head page must be pinned