Make GiST indexes on-disk compatible with 9.2 again.

The patch that turned XLogRecPtr into a uint64 inadvertently changed the
on-disk format of GiST indexes, because the NSN field in the GiST page
opaque is an XLogRecPtr. That breaks pg_upgrade. Revert the format of that
field back to the two-field struct that XLogRecPtr was before. This is the
same we did to LSNs in the page header to avoid changing on-disk format.

Bump catversion, as this invalidates any existing GiST indexes built on
9.3devel.

src/backend/access/gist/gist.c

@@ -240,7 +240,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 		{
 			/* save old rightlink and NSN */
 			oldrlink = GistPageGetOpaque(page)->rightlink;
-			oldnsn = GistPageGetOpaque(page)->nsn;
+			oldnsn = GistPageGetNSN(page);
 
 			dist->buffer = buffer;
 			dist->block.blkno = BufferGetBlockNumber(buffer);
@@ -364,7 +364,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 			 * F_FOLLOW_RIGHT flags ensure that scans will follow the
 			 * rightlinks until the downlinks are inserted.
 			 */
-			GistPageGetOpaque(ptr->page)->nsn = oldnsn;
+			GistPageSetNSN(ptr->page, oldnsn);
 		}
 
 		START_CRIT_SECTION();
@@ -473,7 +473,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 	{
 		Page		leftpg = BufferGetPage(leftchildbuf);
 
-		GistPageGetOpaque(leftpg)->nsn = recptr;
+		GistPageSetNSN(leftpg, recptr);
 		GistClearFollowRight(leftpg);
 
 		PageSetLSN(leftpg, recptr);
@@ -561,7 +561,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace, GISTSTATE *giststate)
 		}
 
 		if (stack->blkno != GIST_ROOT_BLKNO &&
-			stack->parent->lsn < GistPageGetOpaque(stack->page)->nsn)
+			stack->parent->lsn < GistPageGetNSN(stack->page))
 		{
 			/*
 			 * Concurrent split detected. There's no guarantee that the
@@ -707,8 +707,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace, GISTSTATE *giststate)
 					 */
 				}
 				else if (GistFollowRight(stack->page) ||
-						 stack->parent->lsn <
-								  GistPageGetOpaque(stack->page)->nsn)
+						 stack->parent->lsn < GistPageGetNSN(stack->page))
 				{
 					/*
 					 * The page was split while we momentarily unlocked the
@@ -793,7 +792,7 @@ gistFindPath(Relation r, BlockNumber child, OffsetNumber *downlinkoffnum)
 		if (GistFollowRight(page))
 			elog(ERROR, "concurrent GiST page split was incomplete");
 
-		if (top->parent && top->parent->lsn < GistPageGetOpaque(page)->nsn &&
+		if (top->parent && top->parent->lsn < GistPageGetNSN(page) &&
 			GistPageGetOpaque(page)->rightlink != InvalidBlockNumber /* sanity check */ )
 		{
 			/*

src/backend/access/gist/gistget.c

@@ -263,7 +263,7 @@ gistScanPage(IndexScanDesc scan, GISTSearchItem *pageItem, double *myDistances,
 	 */
 	if (!XLogRecPtrIsInvalid(pageItem->data.parentlsn) &&
 		(GistFollowRight(page) ||
-		 pageItem->data.parentlsn < opaque->nsn) &&
+		 pageItem->data.parentlsn < GistPageGetNSN(page)) &&
 		opaque->rightlink != InvalidBlockNumber /* sanity check */ )
 	{
 		/* There was a page split, follow right link to add pages */

src/backend/access/gist/gistvacuum.c

@@ -114,7 +114,7 @@ pushStackIfSplited(Page page, GistBDItem *stack)
 	GISTPageOpaque opaque = GistPageGetOpaque(page);
 
 	if (stack->blkno != GIST_ROOT_BLKNO && !XLogRecPtrIsInvalid(stack->parentlsn) &&
-		(GistFollowRight(page) || stack->parentlsn < opaque->nsn) &&
+		(GistFollowRight(page) || stack->parentlsn < GistPageGetNSN(page)) &&
 		opaque->rightlink != InvalidBlockNumber /* sanity check */ )
 	{
 		/* split page detected, install right link to the stack */

src/backend/access/gist/gistxlog.c

@@ -66,7 +66,7 @@ gistRedoClearFollowRight(XLogRecPtr lsn, XLogRecord *record, int block_index,
 	 */
 	if (lsn >= PageGetLSN(page))
 	{
-		GistPageGetOpaque(page)->nsn = lsn;
+		GistPageSetNSN(page, lsn);
 		GistClearFollowRight(page);
 
 		PageSetLSN(page, lsn);
@@ -271,7 +271,7 @@ gistRedoPageSplitRecord(XLogRecPtr lsn, XLogRecord *record)
 		if (newpage->header->blkno == GIST_ROOT_BLKNO)
 		{
 			GistPageGetOpaque(page)->rightlink = InvalidBlockNumber;
-			GistPageGetOpaque(page)->nsn = xldata->orignsn;
+			GistPageSetNSN(page, xldata->orignsn);
 			GistClearFollowRight(page);
 		}
 		else
@@ -280,7 +280,7 @@ gistRedoPageSplitRecord(XLogRecPtr lsn, XLogRecord *record)
 				GistPageGetOpaque(page)->rightlink = xlrec.page[i + 1].header->blkno;
 			else
 				GistPageGetOpaque(page)->rightlink = xldata->origrlink;
-			GistPageGetOpaque(page)->nsn = xldata->orignsn;
+			GistPageSetNSN(page, xldata->orignsn);
 			if (i < xlrec.data->npage - 1 && !isrootsplit &&
 				xldata->markfollowright)
 				GistMarkFollowRight(page);

src/include/access/gist.h

@@ -64,10 +64,15 @@
 #define F_FOLLOW_RIGHT		(1 << 3)	/* page to the right has no downlink */
 
 typedef XLogRecPtr GistNSN;
+/*
+ * For on-disk compatibility with pre-9.3 servers, NSN is stored as two
+ * 32-bit fields on disk, same as LSNs.
+ */
+typedef PageXLogRecPtr PageGistNSN;
 
 typedef struct GISTPageOpaqueData
 {
-	GistNSN		nsn;			/* this value must change on page split */
+	PageGistNSN	nsn;			/* this value must change on page split */
 	BlockNumber rightlink;		/* next page if any */
 	uint16		flags;			/* see bit definitions above */
 	uint16		gist_page_id;	/* for identification of GiST indexes */
@@ -137,6 +142,9 @@ typedef struct GISTENTRY
 #define GistMarkFollowRight(page) ( GistPageGetOpaque(page)->flags |= F_FOLLOW_RIGHT)
 #define GistClearFollowRight(page)	( GistPageGetOpaque(page)->flags &= ~F_FOLLOW_RIGHT)
 
+#define GistPageGetNSN(page) ( PageXLogRecPtrGet(GistPageGetOpaque(page)->nsn))
+#define GistPageSetNSN(page, val) ( PageXLogRecPtrSet(GistPageGetOpaque(page)->nsn, val))
+
 /*
  * Vector of GISTENTRY structs; user-defined methods union and picksplit
  * take it as one of their arguments

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201212081
+#define CATALOG_VERSION_NO	201301171
 
 #endif

src/include/storage/bufpage.h

@@ -82,6 +82,21 @@ typedef Pointer Page;
 typedef uint16 LocationIndex;
 
 
+/*
+ * For historical reasons, the 64-bit LSN value is stored as two 32-bit
+ * values.
+ */
+typedef struct
+{
+	uint32		xlogid;			/* high bits */
+	uint32		xrecoff;		/* low bits */
+} PageXLogRecPtr;
+
+#define PageXLogRecPtrGet(val) \
+	((uint64) (val).xlogid << 32 | (val).xrecoff)
+#define PageXLogRecPtrSet(ptr, lsn) \
+	((ptr).xlogid = (uint32) ((lsn) >> 32),	(ptr).xrecoff = (uint32) (lsn))
+
 /*
  * disk page organization
  *
@@ -120,13 +135,6 @@ typedef uint16 LocationIndex;
  * are 15 bits.
  */
 
-/* for historical reasons, the LSN is stored as two 32-bit values. */
-typedef struct
-{
-	uint32		xlogid;			/* high bits */
-	uint32		xrecoff;		/* low bits */
-} PageXLogRecPtr;
-
 typedef struct PageHeaderData
 {
 	/* XXX LSN is member of *any* block, not only page-organized ones */
@@ -319,13 +327,13 @@ typedef PageHeaderData *PageHeader;
 	  / sizeof(ItemIdData)))
 
 /*
- * Additional macros for access to page headers
+ * Additional macros for access to page headers. (Beware multiple evaluation
+ * of the arguments!)
  */
 #define PageGetLSN(page) \
-	((uint64) ((PageHeader) (page))->pd_lsn.xlogid << 32 | ((PageHeader) (page))->pd_lsn.xrecoff)
+	PageXLogRecPtrGet(((PageHeader) (page))->pd_lsn)
 #define PageSetLSN(page, lsn) \
-	(((PageHeader) (page))->pd_lsn.xlogid = (uint32) ((lsn) >> 32),	\
-	 ((PageHeader) (page))->pd_lsn.xrecoff = (uint32) (lsn))
+	PageXLogRecPtrSet(((PageHeader) (page))->pd_lsn, lsn)
 
 /* NOTE: only the 16 least significant bits are stored */
 #define PageGetTLI(page) \