Allow some recovery parameters to be changed with reload

Change

archive_cleanup_command
promote_trigger_file
recovery_end_command
recovery_min_apply_delay

from PGC_POSTMASTER to PGC_SIGHUP.  This did not require any further
changes.
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://www.postgresql.org/message-id/flat/ca28011a-cfaa-565c-d622-c1907c33ecf7%402ndquadrant.com

doc/src/sgml/config.sgml

@@ -3081,8 +3081,7 @@ include_dir 'conf.d'
     <para>
      This section describes the settings that apply only for the duration of
      the recovery.  They must be reset for any subsequent recovery you wish to
-     perform.  They can only be set at server start and cannot be changed once
-     recovery has begun.
+     perform.
     </para>
 
     <para>
@@ -3161,6 +3160,10 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         database server shutdown) or an error by the shell (such as command
         not found), then recovery will abort and the server will not start up.
        </para>
+
+       <para>
+        This parameter can only be set at server start.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -3202,6 +3205,10 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         terminated by a signal or an error by the shell (such as command not
         found), a fatal error will be raised.
        </para>
+       <para>
+        This parameter can only be set in the <filename>postgresql.conf</filename>
+        file or on the server command line.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -3227,6 +3234,10 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         signal or an error by the shell (such as command not found), the
         database will not proceed with startup.
        </para>
+       <para>
+        This parameter can only be set in the <filename>postgresql.conf</filename>
+        file or on the server command line.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -3863,7 +3874,8 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
           standby.  Even if this value is not set, you can still promote
           the standby using <command>pg_ctl promote</command> or calling
           <function>pg_promote</function>.
-          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>
@@ -4117,7 +4129,8 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
         </warning>
        </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>

src/backend/utils/misc/guc.c

@@ -2047,7 +2047,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"recovery_min_apply_delay", PGC_POSTMASTER, REPLICATION_STANDBY,
+		{"recovery_min_apply_delay", PGC_SIGHUP, REPLICATION_STANDBY,
 			gettext_noop("Sets the minimum delay for applying changes during recovery."),
 			NULL,
 			GUC_UNIT_MS
@@ -3398,7 +3398,7 @@ static struct config_string ConfigureNamesString[] =
 	},
 
 	{
-		{"archive_cleanup_command", PGC_POSTMASTER, WAL_ARCHIVE_RECOVERY,
+		{"archive_cleanup_command", PGC_SIGHUP, WAL_ARCHIVE_RECOVERY,
 			gettext_noop("Sets the shell command that will be executed at every restart point."),
 			NULL
 		},
@@ -3408,7 +3408,7 @@ static struct config_string ConfigureNamesString[] =
 	},
 
 	{
-		{"recovery_end_command", PGC_POSTMASTER, WAL_ARCHIVE_RECOVERY,
+		{"recovery_end_command", PGC_SIGHUP, WAL_ARCHIVE_RECOVERY,
 			gettext_noop("Sets the shell command that will be executed once at the end of recovery."),
 			NULL
 		},
@@ -3474,7 +3474,7 @@ static struct config_string ConfigureNamesString[] =
 	},
 
 	{
-		{"promote_trigger_file", PGC_POSTMASTER, REPLICATION_STANDBY,
+		{"promote_trigger_file", PGC_SIGHUP, REPLICATION_STANDBY,
 			gettext_noop("Specifies a file name whose presence ends recovery in the standby."),
 			NULL
 		},

src/backend/utils/misc/postgresql.conf.sample

@@ -244,9 +244,7 @@
 				# e.g. 'cp /mnt/server/archivedir/%f %p'
 				# (change requires restart)
 #archive_cleanup_command = ''	# command to execute at every restartpoint
-				# (change requires restart)
 #recovery_end_command = ''	# command to execute at completion of recovery
-				# (change requires restart)
 
 # - Recovery Target -
 
@@ -310,7 +308,6 @@
 #primary_slot_name = ''			# replication slot on sending server
 					# (change requires restart)
 #promote_trigger_file = ''		# file name whose presence ends recovery
-					# (change requires restart)
 #hot_standby = on			# "off" disallows queries during recovery
 					# (change requires restart)
 #max_standby_archive_delay = 30s	# max delay before canceling queries
@@ -329,7 +326,6 @@
 #wal_retrieve_retry_interval = 5s	# time to wait before retrying to
 					# retrieve WAL after a failed attempt
 #recovery_min_apply_delay = 0		# minimum delay for applying changes during recovery
-					# (change requires restart)
 
 # - Subscribers -