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

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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
This commit is contained in:
Tom Lane
2022-04-11 17:43:46 -04:00
parent 9debd12348
commit bd037dc928
9 changed files with 36 additions and 23 deletions
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24
src/backend/access/transam/xlogreader.c
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@ -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,
NULL);
if (!XLogRecGetBlockTagExtended(record, block_id, rnode, forknum, blknum,
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 ||
!record->record->blocks[block_id].in_use)
if (!XLogRecHasBlockRef(record, block_id))
return false;
bkpb = &record->record->blocks[block_id];