Make XLogRecGetBlockTag() throw error if there's no such block.

All but a few existing callers assume without checking that this
function succeeds.  While it probably will, that's a poor excuse for
not checking.  Let's make it return void and instead throw an error
if it doesn't find the block reference.  Callers that actually need
to handle the no-such-block case must now use the underlying function
XLogRecGetBlockTagExtended.

In addition to being a bit less error-prone, this should also serve
to suppress some Coverity complaints about XLogRecGetBlockRefInfo.

While at it, clean up some inconsistency about use of the
XLogRecHasBlockRef macro: make XLogRecGetBlockTagExtended use
that instead of open-coding the same condition, and avoid calling
XLogRecHasBlockRef twice in relevant code paths.  (That is,
calling XLogRecHasBlockRef followed by XLogRecGetBlockTag is now
deprecated: use XLogRecGetBlockTagExtended instead.)

Patch HEAD only; this doesn't seem to have enough value to consider
a back-branch API break.

Discussion: https://postgr.es/m/425039.1649701221@sss.pgh.pa.us

src/backend/access/heap/heapam.c

@@ -9363,7 +9363,7 @@ heap_xlog_update(XLogReaderState *record, bool hot_update)
 	oldtup.t_len = 0;
 
 	XLogRecGetBlockTag(record, 0, &rnode, NULL, &newblk);
-	if (XLogRecGetBlockTag(record, 1, NULL, NULL, &oldblk))
+	if (XLogRecGetBlockTagExtended(record, 1, NULL, NULL, &oldblk, NULL))
 	{
 		/* HOT updates are never done across pages */
 		Assert(!hot_update);

src/backend/access/nbtree/nbtxlog.c

@@ -267,7 +267,7 @@ btree_xlog_split(bool newitemonleft, XLogReaderState *record)
 
 	XLogRecGetBlockTag(record, 0, NULL, NULL, &origpagenumber);
 	XLogRecGetBlockTag(record, 1, NULL, NULL, &rightpagenumber);
-	if (!XLogRecGetBlockTag(record, 2, NULL, NULL, &spagenumber))
+	if (!XLogRecGetBlockTagExtended(record, 2, NULL, NULL, &spagenumber, NULL))
 		spagenumber = P_NONE;
 
 	/*

src/backend/access/rmgrdesc/xlogdesc.c

@@ -219,15 +219,14 @@ XLogRecGetBlockRefInfo(XLogReaderState *record, bool pretty,
 
 	for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
 	{
-		RelFileNode rnode = {InvalidOid, InvalidOid, InvalidOid};
+		RelFileNode rnode;
-		ForkNumber	forknum = InvalidForkNumber;
+		ForkNumber	forknum;
-		BlockNumber blk = InvalidBlockNumber;
+		BlockNumber blk;
 
-		if (!XLogRecHasBlockRef(record, block_id))
+		if (!XLogRecGetBlockTagExtended(record, block_id,
+										&rnode, &forknum, &blk, NULL))
 			continue;
 
-		XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blk);
-
 		if (detailed_format)
 		{
 			/* Get block references in detailed format. */

src/backend/access/transam/xlogreader.c

@@ -37,6 +37,8 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "utils/memutils.h"
+#else
+#include "common/logging.h"
 #endif
 
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
@@ -1918,14 +1920,25 @@ err:
 
 /*
  * Returns information about the block that a block reference refers to.
- * See XLogRecGetBlockTagExtended().
+ *
+ * This is like XLogRecGetBlockTagExtended, except that the block reference
+ * must exist and there's no access to prefetch_buffer.
  */
-bool
+void
 XLogRecGetBlockTag(XLogReaderState *record, uint8 block_id,
 				   RelFileNode *rnode, ForkNumber *forknum, BlockNumber *blknum)
 {
-	return XLogRecGetBlockTagExtended(record, block_id, rnode, forknum, blknum,
+	if (!XLogRecGetBlockTagExtended(record, block_id, rnode, forknum, blknum,
-									  NULL);
+									NULL))
+	{
+#ifndef FRONTEND
+		elog(ERROR, "failed to locate backup block with ID %d in WAL record",
+			 block_id);
+#else
+		pg_fatal("failed to locate backup block with ID %d in WAL record",
+				 block_id);
+#endif
+	}
 }
 
 /*
@@ -1944,8 +1957,7 @@ XLogRecGetBlockTagExtended(XLogReaderState *record, uint8 block_id,
 {
 	DecodedBkpBlock *bkpb;
 
-	if (block_id > record->record->max_block_id ||
+	if (!XLogRecHasBlockRef(record, block_id))
-		!record->record->blocks[block_id].in_use)
 		return false;
 
 	bkpb = &record->record->blocks[block_id];

src/backend/access/transam/xlogrecovery.c

@@ -2172,10 +2172,10 @@ xlog_block_info(StringInfo buf, XLogReaderState *record)
 		ForkNumber	forknum;
 		BlockNumber blk;
 
-		if (!XLogRecHasBlockRef(record, block_id))
+		if (!XLogRecGetBlockTagExtended(record, block_id,
+										&rnode, &forknum, &blk, NULL))
 			continue;
 
-		XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blk);
 		if (forknum != MAIN_FORKNUM)
 			appendStringInfo(buf, "; blkref #%d: rel %u/%u/%u, fork %u, blk %u",
 							 block_id,
@@ -2303,7 +2303,8 @@ verifyBackupPageConsistency(XLogReaderState *record)
 		Buffer		buf;
 		Page		page;
 
-		if (!XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blkno))
+		if (!XLogRecGetBlockTagExtended(record, block_id,
+										&rnode, &forknum, &blkno, NULL))
 		{
 			/*
 			 * WAL record doesn't contain a block reference with the given id.

src/backend/access/transam/xlogutils.c

@@ -369,7 +369,8 @@ XLogReadBufferForRedoExtended(XLogReaderState *record,
 									&prefetch_buffer))
 	{
 		/* Caller specified a bogus block_id */
-		elog(PANIC, "failed to locate backup block with ID %d", block_id);
+		elog(PANIC, "failed to locate backup block with ID %d in WAL record",
+			 block_id);
 	}
 
 	/*

src/bin/pg_rewind/parsexlog.c

@@ -450,7 +450,8 @@ extractPageInfo(XLogReaderState *record)
 		ForkNumber	forknum;
 		BlockNumber blkno;
 
-		if (!XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blkno))
+		if (!XLogRecGetBlockTagExtended(record, block_id,
+										&rnode, &forknum, &blkno, NULL))
 			continue;
 
 		/* We only care about the main fork; others are copied in toto */

src/bin/pg_waldump/pg_waldump.c

@@ -405,11 +405,10 @@ XLogRecordMatchesRelationBlock(XLogReaderState *record,
 		ForkNumber	forknum;
 		BlockNumber blk;
 
-		if (!XLogRecHasBlockRef(record, block_id))
+		if (!XLogRecGetBlockTagExtended(record, block_id,
+										&rnode, &forknum, &blk, NULL))
 			continue;
 
-		XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blk);
-
 		if ((matchFork == InvalidForkNumber || matchFork == forknum) &&
 			(RelFileNodeEquals(matchRnode, emptyRelFileNode) ||
 			 RelFileNodeEquals(matchRnode, rnode)) &&

src/include/access/xlogreader.h

@@ -429,7 +429,7 @@ extern FullTransactionId XLogRecGetFullXid(XLogReaderState *record);
 
 extern bool RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page);
 extern char *XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len);
-extern bool XLogRecGetBlockTag(XLogReaderState *record, uint8 block_id,
+extern void XLogRecGetBlockTag(XLogReaderState *record, uint8 block_id,
 							   RelFileNode *rnode, ForkNumber *forknum,
 							   BlockNumber *blknum);
 extern bool XLogRecGetBlockTagExtended(XLogReaderState *record, uint8 block_id,