Fix assertion failure when running pgbench -s.

MasaoFujii · MasaoFujii · commit 1accf9974821 · 2019-11-07T16:33:58.000+09:00
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
@@ -976,7 +976,7 @@ 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
 			{

Original file line number	Diff line number	Diff line change
`@@ -976,7 +976,7 @@ XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr)`
`976`	`976`	`*`
`977`	`977`	`* Note that record headers are MAXALIGN'ed`
`978`	`978`	`*/`
`979`		`- if (MAXALIGN(header->xlp_rem_len) > (XLOG_BLCKSZ - pageHeaderSize))`
	`979`	`+ if (MAXALIGN(header->xlp_rem_len) >= (XLOG_BLCKSZ - pageHeaderSize))`
`980`	`980`	`tmpRecPtr = targetPagePtr + XLOG_BLCKSZ;`
`981`	`981`	`else`
`982`	`982`	`{`