Allow restore_command parameter to be changed with reload.

MasaoFujii · MasaoFujii · commit 942305a36365 · 2020-12-02T11:00:15.000+09:00
This commit changes restore_command from PGC_POSTMASTER to PGC_SIGHUP. As the side effect of this commit, restore_command can be reset to empty during archive recovery. In this setting, archive recovery tries to replay only WAL files available in pg_wal directory. This is the same behavior as when the command that always fails is specified in restore_command. Note that restore_command still must be specified (not empty) when starting archive recovery, even after applying this commit. This is necessary as the safeguard to prevent users from forgetting to specify restore_command and starting archive recovery. Thanks to Peter Eisentraut, Michael Paquier, Andres Freund, Robert Haas and Anastasia Lubennikova for discussion. Author: Sergei Kornilov Reviewed-by: Kyotaro Horiguchi, Fujii Masao Discussion: https://postgr.es/m/2317771549527294@sas2-985f744271ca.qloud-c.yandex.net
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
@@ -3567,7 +3567,8 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
        </para>
 
        <para>
-        This parameter can only be set at server start.
+        This parameter can only be set in the <filename>postgresql.conf</filename>
+        file or on the server command line.
        </para>
       </listitem>
      </varlistentry>
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
@@ -3699,7 +3699,7 @@ static struct config_string ConfigureNamesString[] =
 	},
 
 	{
-		{"restore_command", PGC_POSTMASTER, WAL_ARCHIVE_RECOVERY,
+		{"restore_command", PGC_SIGHUP, WAL_ARCHIVE_RECOVERY,
 			gettext_noop("Sets the shell command that will be called to retrieve an archived WAL file."),
 			NULL
 		},
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
@@ -253,7 +253,6 @@
 				# placeholders: %p = path of file to restore
 				#               %f = file name only
 				# e.g. 'cp /mnt/server/archivedir/%f %p'
-				# (change requires restart)
 #archive_cleanup_command = ''	# command to execute at every restartpoint
 #recovery_end_command = ''	# command to execute at completion of recovery
 

Original file line number	Diff line number	Diff line change
`@@ -3699,7 +3699,7 @@ static struct config_string ConfigureNamesString[] =`
`3699`	`3699`	`},`
`3700`	`3700`
`3701`	`3701`	`{`
`3702`		`- {"restore_command", PGC_POSTMASTER, WAL_ARCHIVE_RECOVERY,`
	`3702`	`+ {"restore_command", PGC_SIGHUP, WAL_ARCHIVE_RECOVERY,`
`3703`	`3703`	`gettext_noop("Sets the shell command that will be called to retrieve an archived WAL file."),`
`3704`	`3704`	`NULL`
`3705`	`3705`	`},`