Fix full-page writes of internal GIN pages.

Insertion to a non-leaf GIN page didn't make a full-page image of the page,
which is wrong. The code used to do it correctly, but was changed (commit
853d1c3) because the redo-routine didn't
track incomplete splits correctly when the page was restored from a full
page image. Of course, that was not right way to fix it, the redo routine
should've been fixed instead. The redo-routine was surreptitiously fixed
in 2010 (commit 4016bde), so all we need
to do now is revert the code that creates the record to its original form.

This doesn't change the format of the WAL record.

Backpatch to all supported versions.

Author: hlinnaka

src/backend/access/gin/gindatapage.c

@@ -381,7 +381,6 @@ dataPlaceToPage(GinBtree btree, Buffer buf, OffsetNumber off, XLogRecData **prda
 {
 	Page		page = BufferGetPage(buf);
 	int			sizeofitem = GinSizeOfDataPageItem(page);
-	int			cnt = 0;
 
 	/* these must be static so they can be returned to caller */
 	static XLogRecData rdata[3];
@@ -401,32 +400,25 @@ dataPlaceToPage(GinBtree btree, Buffer buf, OffsetNumber off, XLogRecData **prda
 	data.isLeaf = GinPageIsLeaf(page) ? TRUE : FALSE;
 
 	/*
-	 * Prevent full page write if child's split occurs. That is needed to
-	 * remove incomplete splits while replaying WAL
-	 *
-	 * data.updateBlkno contains new block number (of newly created right
-	 * page) for recently splited page.
+	 * For incomplete-split tracking, we need updateBlkno information and the
+	 * inserted item even when we make a full page image of the page, so put
+	 * the buffer reference in a separate XLogRecData entry.
 	 */
-	if (data.updateBlkno == InvalidBlockNumber)
-	{
-		rdata[0].buffer = buf;
-		rdata[0].buffer_std = FALSE;
-		rdata[0].data = NULL;
-		rdata[0].len = 0;
-		rdata[0].next = &rdata[1];
-		cnt++;
-	}
+	rdata[0].buffer = buf;
+	rdata[0].buffer_std = FALSE;
+	rdata[0].data = NULL;
+	rdata[0].len = 0;
+	rdata[0].next = &rdata[1];
 
-	rdata[cnt].buffer = InvalidBuffer;
-	rdata[cnt].data = (char *) &data;
-	rdata[cnt].len = sizeof(ginxlogInsert);
-	rdata[cnt].next = &rdata[cnt + 1];
-	cnt++;
+	rdata[1].buffer = InvalidBuffer;
+	rdata[1].data = (char *) &data;
+	rdata[1].len = sizeof(ginxlogInsert);
+	rdata[1].next = &rdata[2];
 
-	rdata[cnt].buffer = InvalidBuffer;
-	rdata[cnt].data = (GinPageIsLeaf(page)) ? ((char *) (btree->items + btree->curitem)) : ((char *) &(btree->pitem));
-	rdata[cnt].len = sizeofitem;
-	rdata[cnt].next = NULL;
+	rdata[2].buffer = InvalidBuffer;
+	rdata[2].data = (GinPageIsLeaf(page)) ? ((char *) (btree->items + btree->curitem)) : ((char *) &(btree->pitem));
+	rdata[2].len = sizeofitem;
+	rdata[2].next = NULL;
 
 	if (GinPageIsLeaf(page))
 	{
@@ -442,7 +434,7 @@ dataPlaceToPage(GinBtree btree, Buffer buf, OffsetNumber off, XLogRecData **prda
 				btree->curitem++;
 			}
 			data.nitem = btree->curitem - savedPos;
-			rdata[cnt].len = sizeofitem * data.nitem;
+			rdata[2].len = sizeofitem * data.nitem;
 		}
 		else
 		{

src/backend/access/gin/ginentrypage.c

@@ -486,7 +486,6 @@ entryPlaceToPage(GinBtree btree, Buffer buf, OffsetNumber off, XLogRecData **prd
 {
 	Page		page = BufferGetPage(buf);
 	OffsetNumber placed;
-	int			cnt = 0;
 
 	/* these must be static so they can be returned to caller */
 	static XLogRecData rdata[3];
@@ -509,32 +508,25 @@ entryPlaceToPage(GinBtree btree, Buffer buf, OffsetNumber off, XLogRecData **prd
 	data.isLeaf = GinPageIsLeaf(page) ? TRUE : FALSE;
 
 	/*
-	 * Prevent full page write if child's split occurs. That is needed to
-	 * remove incomplete splits while replaying WAL
-	 *
-	 * data.updateBlkno contains new block number (of newly created right
-	 * page) for recently splited page.
+	 * For incomplete-split tracking, we need updateBlkno information and the
+	 * inserted item even when we make a full page image of the page, so put
+	 * the buffer reference in a separate XLogRecData entry.
 	 */
-	if (data.updateBlkno == InvalidBlockNumber)
-	{
-		rdata[0].buffer = buf;
-		rdata[0].buffer_std = TRUE;
-		rdata[0].data = NULL;
-		rdata[0].len = 0;
-		rdata[0].next = &rdata[1];
-		cnt++;
-	}
-
-	rdata[cnt].buffer = InvalidBuffer;
-	rdata[cnt].data = (char *) &data;
-	rdata[cnt].len = sizeof(ginxlogInsert);
-	rdata[cnt].next = &rdata[cnt + 1];
-	cnt++;
+	rdata[0].buffer = buf;
+	rdata[0].buffer_std = TRUE;
+	rdata[0].data = NULL;
+	rdata[0].len = 0;
+	rdata[0].next = &rdata[1];
 
-	rdata[cnt].buffer = InvalidBuffer;
-	rdata[cnt].data = (char *) btree->entry;
-	rdata[cnt].len = IndexTupleSize(btree->entry);
-	rdata[cnt].next = NULL;
+	rdata[1].buffer = InvalidBuffer;
+	rdata[1].data = (char *) &data;
+	rdata[1].len = sizeof(ginxlogInsert);
+	rdata[1].next = &rdata[2];
+
+	rdata[2].buffer = InvalidBuffer;
+	rdata[2].data = (char *) btree->entry;
+	rdata[2].len = IndexTupleSize(btree->entry);
+	rdata[2].next = NULL;
 
 	btree->entry = NULL;
 }