Minor GIN code refactoring.

It makes for cleaner code to have separate Get/Add functions for PostingItems
and ItemPointers.  A few callsites that have to deal with both types need to
be duplicated because of this, but all the callers have to know which one
they're dealing with anyway. Overall, this reduces the amount of casting
required.

Extracted from Alexander Korotkov's larger patch to change the data page
format.

src/backend/access/gin/gindatapage.c

@@ -105,7 +105,7 @@ dataLocateItem(GinBtree btree, GinBtreeStack *stack)
 	{
 		OffsetNumber mid = low + ((high - low) / 2);
 
-		pitem = (PostingItem *) GinDataPageGetItem(page, mid);
+		pitem = GinDataPageGetPostingItem(page, mid);
 
 		if (mid == maxoff)
 		{
@@ -117,7 +117,7 @@ dataLocateItem(GinBtree btree, GinBtreeStack *stack)
 		}
 		else
 		{
-			pitem = (PostingItem *) GinDataPageGetItem(page, mid);
+			pitem = GinDataPageGetPostingItem(page, mid);
 			result = ginCompareItemPointers(btree->items + btree->curitem, &(pitem->key));
 		}
 
@@ -135,7 +135,7 @@ dataLocateItem(GinBtree btree, GinBtreeStack *stack)
 	Assert(high >= FirstOffsetNumber && high <= maxoff);
 
 	stack->off = high;
-	pitem = (PostingItem *) GinDataPageGetItem(page, high);
+	pitem = GinDataPageGetPostingItem(page, high);
 	return PostingItemGetBlockNumber(pitem);
 }
 
@@ -176,7 +176,8 @@ dataLocateLeafItem(GinBtree btree, GinBtreeStack *stack)
 	{
 		OffsetNumber mid = low + ((high - low) / 2);
 
-		result = ginCompareItemPointers(btree->items + btree->curitem, (ItemPointer) GinDataPageGetItem(page, mid));
+		result = ginCompareItemPointers(btree->items + btree->curitem,
+										GinDataPageGetItemPointer(page, mid));
 
 		if (result == 0)
 		{
@@ -210,7 +211,7 @@ dataFindChildPtr(GinBtree btree, Page page, BlockNumber blkno, OffsetNumber stor
 	/* if page isn't changed, we return storedOff */
 	if (storedOff >= FirstOffsetNumber && storedOff <= maxoff)
 	{
-		pitem = (PostingItem *) GinDataPageGetItem(page, storedOff);
+		pitem = GinDataPageGetPostingItem(page, storedOff);
 		if (PostingItemGetBlockNumber(pitem) == blkno)
 			return storedOff;
 
@@ -220,7 +221,7 @@ dataFindChildPtr(GinBtree btree, Page page, BlockNumber blkno, OffsetNumber stor
 		 */
 		for (i = storedOff + 1; i <= maxoff; i++)
 		{
-			pitem = (PostingItem *) GinDataPageGetItem(page, i);
+			pitem = GinDataPageGetPostingItem(page, i);
 			if (PostingItemGetBlockNumber(pitem) == blkno)
 				return i;
 		}
@@ -231,7 +232,7 @@ dataFindChildPtr(GinBtree btree, Page page, BlockNumber blkno, OffsetNumber stor
 	/* last chance */
 	for (i = FirstOffsetNumber; i <= maxoff; i++)
 	{
-		pitem = (PostingItem *) GinDataPageGetItem(page, i);
+		pitem = GinDataPageGetPostingItem(page, i);
 		if (PostingItemGetBlockNumber(pitem) == blkno)
 			return i;
 	}
@@ -251,33 +252,62 @@ dataGetLeftMostPage(GinBtree btree, Page page)
 	Assert(GinPageIsData(page));
 	Assert(GinPageGetOpaque(page)->maxoff >= FirstOffsetNumber);
 
-	pitem = (PostingItem *) GinDataPageGetItem(page, FirstOffsetNumber);
+	pitem = GinDataPageGetPostingItem(page, FirstOffsetNumber);
 	return PostingItemGetBlockNumber(pitem);
 }
 
 /*
- * add ItemPointer or PostingItem to page. data should point to
+ * add ItemPointer to a leaf page.
- * correct value! depending on leaf or non-leaf page
  */
 void
-GinDataPageAddItem(Page page, void *data, OffsetNumber offset)
+GinDataPageAddItemPointer(Page page, ItemPointer data, OffsetNumber offset)
 {
 	OffsetNumber maxoff = GinPageGetOpaque(page)->maxoff;
 	char	   *ptr;
 
+	Assert(GinPageIsLeaf(page));
+
 	if (offset == InvalidOffsetNumber)
 	{
-		ptr = GinDataPageGetItem(page, maxoff + 1);
+		ptr = (char *) GinDataPageGetItemPointer(page, maxoff + 1);
 	}
 	else
 	{
-		ptr = GinDataPageGetItem(page, offset);
+		ptr = (char *) GinDataPageGetItemPointer(page, offset);
 		if (maxoff + 1 - offset != 0)
-			memmove(ptr + GinSizeOfDataPageItem(page),
+			memmove(ptr + sizeof(ItemPointerData),
 					ptr,
-					(maxoff - offset + 1) * GinSizeOfDataPageItem(page));
+					(maxoff - offset + 1) * sizeof(ItemPointerData));
 	}
-	memcpy(ptr, data, GinSizeOfDataPageItem(page));
+	memcpy(ptr, data, sizeof(ItemPointerData));
+
+	GinPageGetOpaque(page)->maxoff++;
+}
+
+/*
+ * add PostingItem to a non-leaf page.
+ */
+void
+GinDataPageAddPostingItem(Page page, PostingItem *data, OffsetNumber offset)
+{
+	OffsetNumber maxoff = GinPageGetOpaque(page)->maxoff;
+	char	   *ptr;
+
+	Assert(!GinPageIsLeaf(page));
+
+	if (offset == InvalidOffsetNumber)
+	{
+		ptr = (char *) GinDataPageGetPostingItem(page, maxoff + 1);
+	}
+	else
+	{
+		ptr = (char *) GinDataPageGetPostingItem(page, offset);
+		if (maxoff + 1 - offset != 0)
+			memmove(ptr + sizeof(PostingItem),
+					ptr,
+					(maxoff - offset + 1) * sizeof(PostingItem));
+	}
+	memcpy(ptr, data, sizeof(PostingItem));
 
 	GinPageGetOpaque(page)->maxoff++;
 }
@@ -294,7 +324,8 @@ GinPageDeletePostingItem(Page page, OffsetNumber offset)
 	Assert(offset >= FirstOffsetNumber && offset <= maxoff);
 
 	if (offset != maxoff)
-		memmove(GinDataPageGetItem(page, offset), GinDataPageGetItem(page, offset + 1),
+		memmove(GinDataPageGetPostingItem(page, offset),
+				GinDataPageGetPostingItem(page, offset + 1),
 				sizeof(PostingItem) * (maxoff - offset));
 
 	GinPageGetOpaque(page)->maxoff--;
@@ -342,7 +373,7 @@ dataPrepareData(GinBtree btree, Page page, OffsetNumber off)
 
 	if (!GinPageIsLeaf(page) && btree->rightblkno != InvalidBlockNumber)
 	{
-		PostingItem *pitem = (PostingItem *) GinDataPageGetItem(page, off);
+		PostingItem *pitem = GinDataPageGetPostingItem(page, off);
 
 		PostingItemSetBlockNumber(pitem, btree->rightblkno);
 		ret = btree->rightblkno;
@@ -418,7 +449,7 @@ dataPlaceToPage(GinBtree btree, Buffer buf, OffsetNumber off, XLogRecData **prda
 
 			while (btree->curitem < btree->nitem)
 			{
-				GinDataPageAddItem(page, btree->items + btree->curitem, off);
+				GinDataPageAddItemPointer(page, btree->items + btree->curitem, off);
 				off++;
 				btree->curitem++;
 			}
@@ -427,12 +458,12 @@ dataPlaceToPage(GinBtree btree, Buffer buf, OffsetNumber off, XLogRecData **prda
 		}
 		else
 		{
-			GinDataPageAddItem(page, btree->items + btree->curitem, off);
+			GinDataPageAddItemPointer(page, btree->items + btree->curitem, off);
 			btree->curitem++;
 		}
 	}
 	else
-		GinDataPageAddItem(page, &(btree->pitem), off);
+		GinDataPageAddPostingItem(page, &(btree->pitem), off);
 }
 
 /*
@@ -448,6 +479,7 @@ dataSplitPage(GinBtree btree, Buffer lbuf, Buffer rbuf, OffsetNumber off, XLogRe
 	OffsetNumber separator;
 	ItemPointer bound;
 	Page		lpage = PageGetTempPageCopy(BufferGetPage(lbuf));
+	bool		isleaf = GinPageIsLeaf(lpage);
 	ItemPointerData oldbound = *GinDataPageGetRightBound(lpage);
 	int			sizeofitem = GinSizeOfDataPageItem(lpage);
 	OffsetNumber maxoff = GinPageGetOpaque(lpage)->maxoff;
@@ -469,10 +501,20 @@ dataSplitPage(GinBtree btree, Buffer lbuf, Buffer rbuf, OffsetNumber off, XLogRe
 		InvalidOffsetNumber : PostingItemGetBlockNumber(&(btree->pitem));
 	data.updateBlkno = dataPrepareData(btree, lpage, off);
 
-	memcpy(vector, GinDataPageGetItem(lpage, FirstOffsetNumber),
+	if (isleaf)
-		   maxoff * sizeofitem);
+	{
+		memcpy(vector,
+			   GinDataPageGetItemPointer(lpage, FirstOffsetNumber),
+			   maxoff * sizeof(ItemPointerData));
+	}
+	else
+	{
+		memcpy(vector,
+			   GinDataPageGetPostingItem(lpage, FirstOffsetNumber),
+			   maxoff * sizeof(PostingItem));
+	}
 
-	if (GinPageIsLeaf(lpage) && GinPageRightMost(lpage) && off > GinPageGetOpaque(lpage)->maxoff)
+	if (isleaf && GinPageRightMost(lpage) && off > GinPageGetOpaque(lpage)->maxoff)
 	{
 		nCopied = 0;
 		while (btree->curitem < btree->nitem &&
@@ -491,7 +533,7 @@ dataSplitPage(GinBtree btree, Buffer lbuf, Buffer rbuf, OffsetNumber off, XLogRe
 		ptr = vector + (off - 1) * sizeofitem;
 		if (maxoff + 1 - off != 0)
 			memmove(ptr + sizeofitem, ptr, (maxoff - off + 1) * sizeofitem);
-		if (GinPageIsLeaf(lpage))
+		if (isleaf)
 		{
 			memcpy(ptr, btree->items + btree->curitem, sizeofitem);
 			btree->curitem++;
@@ -514,19 +556,32 @@ dataSplitPage(GinBtree btree, Buffer lbuf, Buffer rbuf, OffsetNumber off, XLogRe
 	GinInitPage(rpage, GinPageGetOpaque(lpage)->flags, pageSize);
 	GinInitPage(lpage, GinPageGetOpaque(rpage)->flags, pageSize);
 
-	memcpy(GinDataPageGetItem(lpage, FirstOffsetNumber), vector, separator * sizeofitem);
+	if (isleaf)
+		memcpy(GinDataPageGetItemPointer(lpage, FirstOffsetNumber),
+			   vector, separator * sizeof(ItemPointerData));
+	else
+		memcpy(GinDataPageGetPostingItem(lpage, FirstOffsetNumber),
+			   vector, separator * sizeof(PostingItem));
+
 	GinPageGetOpaque(lpage)->maxoff = separator;
-	memcpy(GinDataPageGetItem(rpage, FirstOffsetNumber),
+	if (isleaf)
-		 vector + separator * sizeofitem, (maxoff - separator) * sizeofitem);
+		memcpy(GinDataPageGetItemPointer(rpage, FirstOffsetNumber),
+			   vector + separator * sizeof(ItemPointerData),
+			   (maxoff - separator) * sizeof(ItemPointerData));
+	else
+		memcpy(GinDataPageGetPostingItem(rpage, FirstOffsetNumber),
+			   vector + separator * sizeof(PostingItem),
+			   (maxoff - separator) * sizeof(PostingItem));
+
 	GinPageGetOpaque(rpage)->maxoff = maxoff - separator;
 
 	PostingItemSetBlockNumber(&(btree->pitem), BufferGetBlockNumber(lbuf));
 	if (GinPageIsLeaf(lpage))
-		btree->pitem.key = *(ItemPointerData *) GinDataPageGetItem(lpage,
+		btree->pitem.key = *GinDataPageGetItemPointer(lpage,
 											GinPageGetOpaque(lpage)->maxoff);
 	else
-		btree->pitem.key = ((PostingItem *) GinDataPageGetItem(lpage,
+		btree->pitem.key = GinDataPageGetPostingItem(lpage,
-									  GinPageGetOpaque(lpage)->maxoff))->key;
+									  GinPageGetOpaque(lpage)->maxoff)->key;
 	btree->rightblkno = BufferGetBlockNumber(rbuf);
 
 	/* set up right bound for left page */
@@ -576,11 +631,11 @@ ginDataFillRoot(GinBtree btree, Buffer root, Buffer lbuf, Buffer rbuf)
 
 	li.key = *GinDataPageGetRightBound(lpage);
 	PostingItemSetBlockNumber(&li, BufferGetBlockNumber(lbuf));
-	GinDataPageAddItem(page, &li, InvalidOffsetNumber);
+	GinDataPageAddPostingItem(page, &li, InvalidOffsetNumber);
 
 	ri.key = *GinDataPageGetRightBound(rpage);
 	PostingItemSetBlockNumber(&ri, BufferGetBlockNumber(rbuf));
-	GinDataPageAddItem(page, &ri, InvalidOffsetNumber);
+	GinDataPageAddPostingItem(page, &ri, InvalidOffsetNumber);
 }
 
 void

src/backend/access/gin/ginget.c

@@ -83,7 +83,7 @@ findItemInPostingPage(Page page, ItemPointer item, OffsetNumber *off)
 	 */
 	for (*off = FirstOffsetNumber; *off <= maxoff; (*off)++)
 	{
-		res = ginCompareItemPointers(item, (ItemPointer) GinDataPageGetItem(page, *off));
+		res = ginCompareItemPointers(item, GinDataPageGetItemPointer(page, *off));
 
 		if (res <= 0)
 			return true;
@@ -154,7 +154,7 @@ scanPostingTree(Relation index, GinScanEntry scanEntry,
 			GinPageGetOpaque(page)->maxoff >= FirstOffsetNumber)
 		{
 			tbm_add_tuples(scanEntry->matchBitmap,
-				   (ItemPointer) GinDataPageGetItem(page, FirstOffsetNumber),
+						   GinDataPageGetItemPointer(page, FirstOffsetNumber),
 						   GinPageGetOpaque(page)->maxoff, false);
 			scanEntry->predictNumberResult += GinPageGetOpaque(page)->maxoff;
 		}
@@ -467,7 +467,8 @@ restartScanEntry:
 			 */
 			entry->list = (ItemPointerData *) palloc(BLCKSZ);
 			entry->nlist = GinPageGetOpaque(page)->maxoff;
-			memcpy(entry->list, GinDataPageGetItem(page, FirstOffsetNumber),
+			memcpy(entry->list,
+				   GinDataPageGetItemPointer(page, FirstOffsetNumber),
 				   GinPageGetOpaque(page)->maxoff * sizeof(ItemPointerData));
 
 			LockBuffer(entry->buffer, GIN_UNLOCK);
@@ -587,8 +588,9 @@ entryGetNextItem(GinState *ginstate, GinScanEntry entry)
 				 * Found position equal to or greater than stored
 				 */
 				entry->nlist = GinPageGetOpaque(page)->maxoff;
-				memcpy(entry->list, GinDataPageGetItem(page, FirstOffsetNumber),
+				memcpy(entry->list,
-				   GinPageGetOpaque(page)->maxoff * sizeof(ItemPointerData));
+					   GinDataPageGetItemPointer(page, FirstOffsetNumber),
+					   GinPageGetOpaque(page)->maxoff * sizeof(ItemPointerData));
 
 				LockBuffer(entry->buffer, GIN_UNLOCK);
 

src/backend/access/gin/ginvacuum.c

@@ -210,7 +210,7 @@ ginVacuumPostingTreeLeaves(GinVacuumState *gvs, BlockNumber blkno, bool isRoot,
 
 		for (i = FirstOffsetNumber; i <= GinPageGetOpaque(page)->maxoff; i++)
 		{
-			PostingItem *pitem = (PostingItem *) GinDataPageGetItem(page, i);
+			PostingItem *pitem = GinDataPageGetPostingItem(page, i);
 
 			if (ginVacuumPostingTreeLeaves(gvs, PostingItemGetBlockNumber(pitem), FALSE, NULL))
 				isChildHasVoid = TRUE;
@@ -283,7 +283,7 @@ ginDeletePage(GinVacuumState *gvs, BlockNumber deleteBlkno, BlockNumber leftBlkn
 #ifdef USE_ASSERT_CHECKING
 	do
 	{
-		PostingItem *tod = (PostingItem *) GinDataPageGetItem(parentPage, myoff);
+		PostingItem *tod = GinDataPageGetPostingItem(parentPage, myoff);
 
 		Assert(PostingItemGetBlockNumber(tod) == deleteBlkno);
 	} while (0);
@@ -422,7 +422,7 @@ ginScanToDelete(GinVacuumState *gvs, BlockNumber blkno, bool isRoot, DataPageDel
 		me->blkno = blkno;
 		for (i = FirstOffsetNumber; i <= GinPageGetOpaque(page)->maxoff; i++)
 		{
-			PostingItem *pitem = (PostingItem *) GinDataPageGetItem(page, i);
+			PostingItem *pitem = GinDataPageGetPostingItem(page, i);
 
 			if (ginScanToDelete(gvs, PostingItemGetBlockNumber(pitem), FALSE, me, i))
 				i--;

src/backend/access/gin/ginxlog.c

@@ -189,7 +189,7 @@ ginRedoInsert(XLogRecPtr lsn, XLogRecord *record)
 				Assert(data->updateBlkno == InvalidBlockNumber);
 
 				for (i = 0; i < data->nitem; i++)
-					GinDataPageAddItem(page, items + i, data->offset + i);
+					GinDataPageAddItemPointer(page, &items[i], data->offset + i);
 			}
 			else
 			{
@@ -200,13 +200,13 @@ ginRedoInsert(XLogRecPtr lsn, XLogRecord *record)
 				if (data->updateBlkno != InvalidBlockNumber)
 				{
 					/* update link to right page after split */
-					pitem = (PostingItem *) GinDataPageGetItem(page, data->offset);
+					pitem = GinDataPageGetPostingItem(page, data->offset);
 					PostingItemSetBlockNumber(pitem, data->updateBlkno);
 				}
 
 				pitem = (PostingItem *) (XLogRecGetData(record) + sizeof(ginxlogInsert));
 
-				GinDataPageAddItem(page, pitem, data->offset);
+				GinDataPageAddPostingItem(page, pitem, data->offset);
 			}
 		}
 		else
@@ -286,22 +286,28 @@ ginRedoSplit(XLogRecPtr lsn, XLogRecord *record)
 
 		for (i = 0; i < data->separator; i++)
 		{
-			GinDataPageAddItem(lpage, ptr, InvalidOffsetNumber);
+			if (data->isLeaf)
+				GinDataPageAddItemPointer(lpage, (ItemPointer) ptr, InvalidOffsetNumber);
+			else
+				GinDataPageAddPostingItem(lpage, (PostingItem *) ptr, InvalidOffsetNumber);
 			ptr += sizeofitem;
 		}
 
 		for (i = data->separator; i < data->nitem; i++)
 		{
-			GinDataPageAddItem(rpage, ptr, InvalidOffsetNumber);
+			if (data->isLeaf)
+				GinDataPageAddItemPointer(rpage, (ItemPointer) ptr, InvalidOffsetNumber);
+			else
+				GinDataPageAddPostingItem(rpage, (PostingItem *) ptr, InvalidOffsetNumber);
 			ptr += sizeofitem;
 		}
 
 		/* set up right key */
 		bound = GinDataPageGetRightBound(lpage);
 		if (data->isLeaf)
-			*bound = *(ItemPointerData *) GinDataPageGetItem(lpage, GinPageGetOpaque(lpage)->maxoff);
+			*bound = *GinDataPageGetItemPointer(lpage, GinPageGetOpaque(lpage)->maxoff);
 		else
-			*bound = ((PostingItem *) GinDataPageGetItem(lpage, GinPageGetOpaque(lpage)->maxoff))->key;
+			*bound = GinDataPageGetPostingItem(lpage, GinPageGetOpaque(lpage)->maxoff)->key;
 
 		bound = GinDataPageGetRightBound(rpage);
 		*bound = data->rightbound;
@@ -803,11 +809,11 @@ ginContinueSplit(ginIncompleteSplit *split)
 
 		PostingItemSetBlockNumber(&(btree.pitem), split->leftBlkno);
 		if (GinPageIsLeaf(page))
-			btree.pitem.key = *(ItemPointerData *) GinDataPageGetItem(page,
+			btree.pitem.key = *GinDataPageGetItemPointer(page,
-											 GinPageGetOpaque(page)->maxoff);
+														 GinPageGetOpaque(page)->maxoff);
 		else
-			btree.pitem.key = ((PostingItem *) GinDataPageGetItem(page,
+			btree.pitem.key = GinDataPageGetPostingItem(page,
-									   GinPageGetOpaque(page)->maxoff))->key;
+														GinPageGetOpaque(page)->maxoff)->key;
 	}
 
 	btree.rightblkno = split->rightBlkno;

src/include/access/gin_private.h

@@ -232,10 +232,14 @@ typedef signed char GinNullCategory;
 #define GinDataPageGetRightBound(page)	((ItemPointer) PageGetContents(page))
 #define GinDataPageGetData(page)	\
 	(PageGetContents(page) + MAXALIGN(sizeof(ItemPointerData)))
+/* non-leaf pages contain PostingItems */
+#define GinDataPageGetPostingItem(page, i)	\
+	((PostingItem *) (GinDataPageGetData(page) + ((i)-1) * sizeof(PostingItem)))
+/* leaf pages contain ItemPointers */
+#define GinDataPageGetItemPointer(page, i)	\
+	((ItemPointer) (GinDataPageGetData(page) + ((i)-1) * sizeof(ItemPointerData)))
 #define GinSizeOfDataPageItem(page) \
 	(GinPageIsLeaf(page) ? sizeof(ItemPointerData) : sizeof(PostingItem))
-#define GinDataPageGetItem(page,i)	\
-	(GinDataPageGetData(page) + ((i)-1) * GinSizeOfDataPageItem(page))
 
 #define GinDataPageGetFreeSpace(page)	\
 	(BLCKSZ - MAXALIGN(SizeOfPageHeaderData) \
@@ -534,7 +538,8 @@ extern uint32 ginMergeItemPointers(ItemPointerData *dst,
 					 ItemPointerData *a, uint32 na,
 					 ItemPointerData *b, uint32 nb);
 
-extern void GinDataPageAddItem(Page page, void *data, OffsetNumber offset);
+extern void GinDataPageAddItemPointer(Page page, ItemPointer data, OffsetNumber offset);
+extern void GinDataPageAddPostingItem(Page page, PostingItem *data, OffsetNumber offset);
 extern void GinPageDeletePostingItem(Page page, OffsetNumber offset);
 
 typedef struct