Refactor per-page logic common to all redo routines to a new function.

Every redo routine uses the same idiom to determine what to do to a page:
check if there's a backup block for it, and if not read, the buffer if the
block exists, and check its LSN. Refactor that into a common function,
XLogReadBufferForRedo, making all the redo routines shorter and more
readable.

This has no user-visible effect, and makes no changes to the WAL format.

Reviewed by Andres Freund, Alvaro Herrera, Michael Paquier.

Author: hlinnaka

src/backend/access/gin/ginxlog.c

@@ -20,25 +20,25 @@
 static MemoryContext opCtx;		/* working memory for operations */
 
 static void
-ginRedoClearIncompleteSplit(XLogRecPtr lsn, RelFileNode node, BlockNumber blkno)
+ginRedoClearIncompleteSplit(XLogRecPtr lsn, XLogRecord *record,
+							int block_index,
+							RelFileNode node, BlockNumber blkno)
 {
 	Buffer		buffer;
 	Page		page;
 
-	buffer = XLogReadBuffer(node, blkno, false);
-	if (!BufferIsValid(buffer))
-		return;					/* page was deleted, nothing to do */
-	page = (Page) BufferGetPage(buffer);
-
-	if (lsn > PageGetLSN(page))
+	if (XLogReadBufferForRedo(lsn, record, block_index, node, blkno, &buffer)
+		== BLK_NEEDS_REDO)
 	{
+		page = (Page) BufferGetPage(buffer);
+
 		GinPageGetOpaque(page)->flags &= ~GIN_INCOMPLETE_SPLIT;
 
 		PageSetLSN(page, lsn);
 		MarkBufferDirty(buffer);
 	}
-
-	UnlockReleaseBuffer(buffer);
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
 }
 
 static void
@@ -332,7 +332,6 @@ ginRedoInsert(XLogRecPtr lsn, XLogRecord *record)
 {
 	ginxlogInsert *data = (ginxlogInsert *) XLogRecGetData(record);
 	Buffer		buffer;
-	Page		page;
 	char	   *payload;
 	BlockNumber leftChildBlkno = InvalidBlockNumber;
 	BlockNumber rightChildBlkno = InvalidBlockNumber;
@@ -351,26 +350,14 @@ ginRedoInsert(XLogRecPtr lsn, XLogRecord *record)
 		rightChildBlkno = BlockIdGetBlockNumber((BlockId) payload);
 		payload += sizeof(BlockIdData);
 
-		if (record->xl_info & XLR_BKP_BLOCK(0))
-			(void) RestoreBackupBlock(lsn, record, 0, false, false);
-		else
-			ginRedoClearIncompleteSplit(lsn, data->node, leftChildBlkno);
+		ginRedoClearIncompleteSplit(lsn, record, 0, data->node, leftChildBlkno);
 	}
 
-	/* If we have a full-page image, restore it and we're done */
-	if (record->xl_info & XLR_BKP_BLOCK(isLeaf ? 0 : 1))
+	if (XLogReadBufferForRedo(lsn, record, isLeaf ? 0 : 1, data->node,
+							  data->blkno, &buffer) == BLK_NEEDS_REDO)
 	{
-		(void) RestoreBackupBlock(lsn, record, isLeaf ? 0 : 1, false, false);
-		return;
-	}
-
-	buffer = XLogReadBuffer(data->node, data->blkno, false);
-	if (!BufferIsValid(buffer))
-		return;					/* page was deleted, nothing to do */
-	page = (Page) BufferGetPage(buffer);
+		Page		page = BufferGetPage(buffer);
 
-	if (lsn > PageGetLSN(page))
-	{
 		/* How to insert the payload is tree-type specific */
 		if (data->flags & GIN_INSERT_ISDATA)
 		{
@@ -386,8 +373,8 @@ ginRedoInsert(XLogRecPtr lsn, XLogRecord *record)
 		PageSetLSN(page, lsn);
 		MarkBufferDirty(buffer);
 	}
-
-	UnlockReleaseBuffer(buffer);
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
 }
 
 static void
@@ -476,12 +463,7 @@ ginRedoSplit(XLogRecPtr lsn, XLogRecord *record)
 	 * split
 	 */
 	if (!isLeaf)
-	{
-		if (record->xl_info & XLR_BKP_BLOCK(0))
-			(void) RestoreBackupBlock(lsn, record, 0, false, false);
-		else
-			ginRedoClearIncompleteSplit(lsn, data->node, data->leftChildBlkno);
-	}
+		ginRedoClearIncompleteSplit(lsn, record, 0, data->node, data->leftChildBlkno);
 
 	flags = 0;
 	if (isLeaf)
@@ -605,31 +587,21 @@ ginRedoVacuumDataLeafPage(XLogRecPtr lsn, XLogRecord *record)
 {
 	ginxlogVacuumDataLeafPage *xlrec = (ginxlogVacuumDataLeafPage *) XLogRecGetData(record);
 	Buffer		buffer;
-	Page		page;
 
-	/* If we have a full-page image, restore it and we're done */
-	if (record->xl_info & XLR_BKP_BLOCK(0))
+	if (XLogReadBufferForRedo(lsn, record, 0, xlrec->node, xlrec->blkno,
+							  &buffer) == BLK_NEEDS_REDO)
 	{
-		(void) RestoreBackupBlock(lsn, record, 0, false, false);
-		return;
-	}
-
-	buffer = XLogReadBuffer(xlrec->node, xlrec->blkno, false);
-	if (!BufferIsValid(buffer))
-		return;
-	page = (Page) BufferGetPage(buffer);
+		Page		page = BufferGetPage(buffer);
 
-	Assert(GinPageIsLeaf(page));
-	Assert(GinPageIsData(page));
+		Assert(GinPageIsLeaf(page));
+		Assert(GinPageIsData(page));
 
-	if (lsn > PageGetLSN(page))
-	{
 		ginRedoRecompress(page, &xlrec->data);
 		PageSetLSN(page, lsn);
 		MarkBufferDirty(buffer);
 	}
-
-	UnlockReleaseBuffer(buffer);
+	if (BufferIsValid(buffer))
+		UnlockReleaseBuffer(buffer);
 }
 
 static void
@@ -641,62 +613,42 @@ ginRedoDeletePage(XLogRecPtr lsn, XLogRecord *record)
 	Buffer		lbuffer;
 	Page		page;
 
-	if (record->xl_info & XLR_BKP_BLOCK(0))
-		dbuffer = RestoreBackupBlock(lsn, record, 0, false, true);
-	else
+	if (XLogReadBufferForRedo(lsn, record, 0, data->node, data->blkno, &dbuffer)
+		== BLK_NEEDS_REDO)
 	{
-		dbuffer = XLogReadBuffer(data->node, data->blkno, false);
-		if (BufferIsValid(dbuffer))
-		{
-			page = BufferGetPage(dbuffer);
-			if (lsn > PageGetLSN(page))
-			{
-				Assert(GinPageIsData(page));
-				GinPageGetOpaque(page)->flags = GIN_DELETED;
-				PageSetLSN(page, lsn);
-				MarkBufferDirty(dbuffer);
-			}
-		}
+		page = BufferGetPage(dbuffer);
+
+		Assert(GinPageIsData(page));
+		GinPageGetOpaque(page)->flags = GIN_DELETED;
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(dbuffer);
 	}
 
-	if (record->xl_info & XLR_BKP_BLOCK(1))
-		pbuffer = RestoreBackupBlock(lsn, record, 1, false, true);
-	else
+	if (XLogReadBufferForRedo(lsn, record, 1, data->node, data->parentBlkno,
+							  &pbuffer) == BLK_NEEDS_REDO)
 	{
-		pbuffer = XLogReadBuffer(data->node, data->parentBlkno, false);
-		if (BufferIsValid(pbuffer))
-		{
-			page = BufferGetPage(pbuffer);
-			if (lsn > PageGetLSN(page))
-			{
-				Assert(GinPageIsData(page));
-				Assert(!GinPageIsLeaf(page));
-				GinPageDeletePostingItem(page, data->parentOffset);
-				PageSetLSN(page, lsn);
-				MarkBufferDirty(pbuffer);
-			}
-		}
+		page = BufferGetPage(pbuffer);
+
+		Assert(GinPageIsData(page));
+		Assert(!GinPageIsLeaf(page));
+		GinPageDeletePostingItem(page, data->parentOffset);
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(pbuffer);
 	}
 
-	if (record->xl_info & XLR_BKP_BLOCK(2))
-		(void) RestoreBackupBlock(lsn, record, 2, false, false);
-	else if (data->leftBlkno != InvalidBlockNumber)
+	if (XLogReadBufferForRedo(lsn, record, 2, data->node, data->leftBlkno,
+							  &lbuffer) == BLK_NEEDS_REDO)
 	{
-		lbuffer = XLogReadBuffer(data->node, data->leftBlkno, false);
-		if (BufferIsValid(lbuffer))
-		{
-			page = BufferGetPage(lbuffer);
-			if (lsn > PageGetLSN(page))
-			{
-				Assert(GinPageIsData(page));
-				GinPageGetOpaque(page)->rightlink = data->rightLink;
-				PageSetLSN(page, lsn);
-				MarkBufferDirty(lbuffer);
-			}
-			UnlockReleaseBuffer(lbuffer);
-		}
+		page = BufferGetPage(lbuffer);
+
+		Assert(GinPageIsData(page));
+		GinPageGetOpaque(page)->rightlink = data->rightLink;
+		PageSetLSN(page, lsn);
+		MarkBufferDirty(lbuffer);
 	}
 
+	if (BufferIsValid(lbuffer))
+		UnlockReleaseBuffer(lbuffer);
 	if (BufferIsValid(pbuffer))
 		UnlockReleaseBuffer(pbuffer);
 	if (BufferIsValid(dbuffer))
@@ -730,74 +682,64 @@ ginRedoUpdateMetapage(XLogRecPtr lsn, XLogRecord *record)
 		/*
 		 * insert into tail page
 		 */
-		if (record->xl_info & XLR_BKP_BLOCK(0))
-			(void) RestoreBackupBlock(lsn, record, 0, false, false);
-		else
+		if (XLogReadBufferForRedo(lsn, record, 0, data->node,
+								  data->metadata.tail, &buffer)
+			== BLK_NEEDS_REDO)
 		{
-			buffer = XLogReadBuffer(data->node, data->metadata.tail, false);
-			if (BufferIsValid(buffer))
-			{
-				Page		page = BufferGetPage(buffer);
+			Page		page = BufferGetPage(buffer);
+			OffsetNumber off;
+			int			i;
+			Size		tupsize;
+			IndexTuple	tuples;
 
-				if (lsn > PageGetLSN(page))
-				{
-					OffsetNumber l,
-								off = (PageIsEmpty(page)) ? FirstOffsetNumber :
-					OffsetNumberNext(PageGetMaxOffsetNumber(page));
-					int			i,
-								tupsize;
-					IndexTuple	tuples = (IndexTuple) (XLogRecGetData(record) + sizeof(ginxlogUpdateMeta));
+			tuples = (IndexTuple) (XLogRecGetData(record) + sizeof(ginxlogUpdateMeta));
 
-					for (i = 0; i < data->ntuples; i++)
-					{
-						tupsize = IndexTupleSize(tuples);
+			if (PageIsEmpty(page))
+				off = FirstOffsetNumber;
+			else
+				off = OffsetNumberNext(PageGetMaxOffsetNumber(page));
 
-						l = PageAddItem(page, (Item) tuples, tupsize, off, false, false);
+			for (i = 0; i < data->ntuples; i++)
+			{
+				tupsize = IndexTupleSize(tuples);
 
-						if (l == InvalidOffsetNumber)
-							elog(ERROR, "failed to add item to index page");
+				if (PageAddItem(page, (Item) tuples, tupsize, off,
+								false, false) == InvalidOffsetNumber)
+					elog(ERROR, "failed to add item to index page");
 
-						tuples = (IndexTuple) (((char *) tuples) + tupsize);
+				tuples = (IndexTuple) (((char *) tuples) + tupsize);
 
-						off++;
-					}
+				off++;
+			}
 
-					/*
-					 * Increase counter of heap tuples
-					 */
-					GinPageGetOpaque(page)->maxoff++;
+			/*
+			 * Increase counter of heap tuples
+			 */
+			GinPageGetOpaque(page)->maxoff++;
 
-					PageSetLSN(page, lsn);
-					MarkBufferDirty(buffer);
-				}
-				UnlockReleaseBuffer(buffer);
-			}
+			PageSetLSN(page, lsn);
+			MarkBufferDirty(buffer);
 		}
+		if (BufferIsValid(buffer))
+			UnlockReleaseBuffer(buffer);
 	}
 	else if (data->prevTail != InvalidBlockNumber)
 	{
 		/*
 		 * New tail
 		 */
-		if (record->xl_info & XLR_BKP_BLOCK(0))
-			(void) RestoreBackupBlock(lsn, record, 0, false, false);
-		else
+		if (XLogReadBufferForRedo(lsn, record, 0, data->node, data->prevTail,
+								  &buffer) == BLK_NEEDS_REDO)
 		{
-			buffer = XLogReadBuffer(data->node, data->prevTail, false);
-			if (BufferIsValid(buffer))
-			{
-				Page		page = BufferGetPage(buffer);
+			Page		page = BufferGetPage(buffer);
 
-				if (lsn > PageGetLSN(page))
-				{
-					GinPageGetOpaque(page)->rightlink = data->newRightlink;
+			GinPageGetOpaque(page)->rightlink = data->newRightlink;
 
-					PageSetLSN(page, lsn);
-					MarkBufferDirty(buffer);
-				}
-				UnlockReleaseBuffer(buffer);
-			}
+			PageSetLSN(page, lsn);
+			MarkBufferDirty(buffer);
 		}
+		if (BufferIsValid(buffer))
+			UnlockReleaseBuffer(buffer);
 	}
 
 	UnlockReleaseBuffer(metabuffer);