From f5f20625b1f297cac177917c6e9b1f110ffea707 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Wed, 25 Mar 2020 20:54:27 -0300
Subject: [PATCH v10 3/3] Set wal_receiver_create_temp_slot as PGC_SIGHUP

.. using the new infrastructure
---
 doc/src/sgml/config.sgml                      |  6 +++++-
 src/backend/postmaster/startup.c              | 10 +++++++++-
 src/backend/utils/misc/guc.c                  |  2 +-
 src/backend/utils/misc/postgresql.conf.sample |  1 -
 4 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 4d17dafa7e..c5160fe907 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4173,7 +4173,11 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
         Specifies whether a WAL receiver should create a temporary replication
         slot on the remote instance when no permanent replication slot to use
         has been configured (using <xref linkend="guc-primary-slot-name"/>).
-        The default is off.  This parameter can only be set at server start.
+        The default is off.  This parameter can only be set in the 
+        <filename>postgresql.conf</filename> file or on the server command line.
+       </para>
+       <para>
+        The WAL receiver is restarted after an update of <varname>wal_receiver_create_temp_slot</varname>.
        </para>
       </listitem>
      </varlistentry>
diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index f35b5adf7d..fd9ac35dac 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -107,18 +107,26 @@ StartupRereadConfig(void)
 {
 	char	   *conninfo = pstrdup(PrimaryConnInfo);
 	char	   *slotname = pstrdup(PrimarySlotName);
+	bool		tempSlot = wal_receiver_create_temp_slot;
 	bool		conninfoChanged;
 	bool		slotnameChanged;
+	bool		tempSlotChanged = false;
 
 	ProcessConfigFile(PGC_SIGHUP);
 
 	conninfoChanged = strcmp(conninfo, PrimaryConnInfo) != 0;
 	slotnameChanged = strcmp(slotname, PrimarySlotName) != 0;
 
+	/*
+	 * wal_receiver_create_temp_slot is used only when we have no slot
+	 * configured.  We do not need to track this change if it has no effect.
+	 */
+	if (!slotnameChanged && strcmp(PrimarySlotName, "") == 0)
+		tempSlotChanged = tempSlot != wal_receiver_create_temp_slot;
 	pfree(conninfo);
 	pfree(slotname);
 
-	if (conninfoChanged || slotnameChanged)
+	if (conninfoChanged || slotnameChanged || tempSlotChanged)
 		StartupRequestWalReceiverRestart();
 }
 
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 2d149dfaa5..53665971f5 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2050,7 +2050,7 @@ static struct config_bool ConfigureNamesBool[] =
 	},
 
 	{
-		{"wal_receiver_create_temp_slot", PGC_POSTMASTER, REPLICATION_STANDBY,
+		{"wal_receiver_create_temp_slot", PGC_SIGHUP, REPLICATION_STANDBY,
 			gettext_noop("Sets whether a WAL receiver should create a temporary replication slot if no permanent slot is configured."),
 		},
 		&wal_receiver_create_temp_slot,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 31096725fd..f01e43b818 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -321,7 +321,6 @@
 					# -1 allows indefinite delay
 #wal_receiver_create_temp_slot = off	# Create temp slot if primary_slot_name
 					# is not set.
-					# (change requires restart)
 #wal_receiver_status_interval = 10s	# send replies at least this often
 					# 0 disables
 #hot_standby_feedback = off		# send info from standby to prevent
-- 
2.20.1