Improve some comments in pg_checksums about the needed clean shutdown

michaelpq · michaelpq · commit 84d4de97e8d1 · 2019-06-07T20:48:39.000+09:00
It was not clear from the code why it is necessary. And we need a clean shutdown to avoid random checksum failures caused by torn pages. Author: Masahiko Sawada Discussion: https://postgr.es/m/CAD21AoDum5MbAb7F=pa9dOD1W2tukuDMPzWT7NjZceNoWB_6Qw@mail.gmail.com
diff --git a/src/bin/pg_checksums/pg_checksums.c b/src/bin/pg_checksums/pg_checksums.c
@@ -475,7 +475,7 @@ main(int argc, char *argv[])
 		exit(1);
 	}
 
-	/* Check if cluster is running */
+	/* Read the control file and check compatibility */
 	ControlFile = get_controlfile(DataDir, &crc_ok);
 	if (!crc_ok)
 	{
@@ -497,6 +497,11 @@ main(int argc, char *argv[])
 		exit(1);
 	}
 
+	/*
+	 * Check if cluster is running.  A clean shutdown is required to avoid
+	 * random checksum failures caused by torn pages.  Note that this doesn't
+	 * guard against someone starting the cluster concurrently.
+	 */
 	if (ControlFile->state != DB_SHUTDOWNED &&
 		ControlFile->state != DB_SHUTDOWNED_IN_RECOVERY)
 	{

Original file line number	Diff line number	Diff line change
`@@ -475,7 +475,7 @@ main(int argc, char *argv[])`
`475`	`475`	`exit(1);`
`476`	`476`	`}`
`477`	`477`
`478`		`- /* Check if cluster is running */`
	`478`	`+ /* Read the control file and check compatibility */`
`479`	`479`	`ControlFile = get_controlfile(DataDir, &crc_ok);`
`480`	`480`	`if (!crc_ok)`
`481`	`481`	`{`
`@@ -497,6 +497,11 @@ main(int argc, char *argv[])`
`497`	`497`	`exit(1);`
`498`	`498`	`}`
`499`	`499`
	`500`	`+ /*`
	`501`	`+ * Check if cluster is running. A clean shutdown is required to avoid`
	`502`	`+ * random checksum failures caused by torn pages. Note that this doesn't`
	`503`	`+ * guard against someone starting the cluster concurrently.`
	`504`	`+ */`
`500`	`505`	`if (ControlFile->state != DB_SHUTDOWNED &&`
`501`	`506`	`ControlFile->state != DB_SHUTDOWNED_IN_RECOVERY)`
`502`	`507`	`{`