Fix assertion failure when running pgbench -s.

If there is the WAL page that the continuation WAL record just fits within
(i.e., the continuation record ends just at the end of the page) and
the LSN in such page is specified with -s option, previously pg_waldump
caused an assertion failure. The cause of this assertion failure was that
XLogFindNextRecord() that pg_waldump -s calls mistakenly handled
such special WAL page.

This commit changes XLogFindNextRecord() so that it can handle
such WAL page correctly.

Back-patch to all supported versions.

Author: Andrey Lepikhov
Reviewed-by: Fujii Masao, Michael Paquier
Discussion: https://postgr.es/m/99303554-5dd5-06e6-f943-b3005ccd6edd@postgrespro.ru

diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 2a2cbfb3fc874096c36efb776d4e3c7a43ef9ae0..a1ad36fbeb895036c803ffd6453bf8db7e7afdde 100644 (file)
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -954,7 +954,7 @@ XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr)
             *
             * Note that record headers are MAXALIGN'ed
             */
-           if (MAXALIGN(header->xlp_rem_len) > (XLOG_BLCKSZ - pageHeaderSize))
+           if (MAXALIGN(header->xlp_rem_len) >= (XLOG_BLCKSZ - pageHeaderSize))
                tmpRecPtr = targetPagePtr + XLOG_BLCKSZ;
            else
            {