Make self-referencing foreign key on repl_nodes table deferrable

sql/repmgr3.1.1_repmgr3.1.2.sql

@@ -0,0 +1,31 @@
+/*
+ * Update a repmgr 3.1.1 installation to repmgr 3.1.2
+ * --------------------------------------------------
+ *
+ * This update is only required if repmgrd is being used in conjunction
+ * with a witness server.
+ *
+ * The new repmgr package should be installed first. Then
+ * carry out these steps:
+ *
+ *   1. (If repmgrd is used) stop any running repmgrd instances
+ *   2. On the master node, execute the SQL statement listed below
+ *   3. (If repmgrd is used) restart repmgrd
+ */
+
+/*
+ * If your repmgr installation is not included in your repmgr
+ * user's search path, please set the search path to the name
+ * of the repmgr schema to ensure objects are installed in
+ * the correct location.
+ *
+ * The repmgr schema is  "repmgr_" + the cluster name defined in
+ * 'repmgr.conf'.
+ */
+
+-- SET search_path TO 'name_of_repmgr_schema';
+
+BEGIN;
+
+ALTER TABLE repl_nodes ALTER CONSTRAINT repl_nodes_upstream_node_id_fkey DEFERRABLE;
+COMMIT;