gp_activate_standby() doesn't need to be callable from SQL.

src/backend/access/transam/xlog.c

@@ -6558,7 +6558,7 @@ UpdateCatalogForStandbyPromotion(void)
 	Gp_role = GP_ROLE_UTILITY;
 	StartTransactionCommand();
 	GetTransactionSnapshot();
-	DirectFunctionCall1(gp_activate_standby, (Datum) 0);
+	gp_activate_standby();
 	/* close the transaction we started above */
 	CommitTransactionCommand();
 	Gp_role = old_role;

src/backend/utils/gp/segadmin.c

@@ -850,8 +850,8 @@ catalog_activate_standby(int16 standbydbid, int16 olddbid)
  * Returns:
  *  true upon success, otherwise throws error.
  */
-Datum
-gp_activate_standby(PG_FUNCTION_ARGS)
+bool
+gp_activate_standby(void)
 {
 	int16		olddbid = GpIdentity.dbid;
 	int16		newdbid;
@@ -872,7 +872,7 @@ gp_activate_standby(PG_FUNCTION_ARGS)
 		 * Job is already done, nothing needs to be done. We mostly crashed
 		 * after updating the catalogs.
 		 */
-		PG_RETURN_BOOL(true);
+		return true;
 	}
 
 	mirroring_sanity_check(SUPERUSER | UTILITY_MODE | STANDBY_ONLY,
@@ -888,7 +888,7 @@ gp_activate_standby(PG_FUNCTION_ARGS)
 	primaryMirrorSetNewDbid(newdbid);
 
 	/* done */
-	PG_RETURN_BOOL(true);
+	return true;
 }
 
 Datum

src/include/catalog/pg_proc.sql

@@ -362,8 +362,6 @@
 
  CREATE FUNCTION gp_remove_segment(int2) RETURNS bool LANGUAGE internal VOLATILE AS 'gp_remove_segment' WITH (OID=5051, DESCRIPTION="Remove a primary segment from the system catalog");
 
- CREATE FUNCTION gp_activate_standby() RETURNS bool LANGUAGE internal VOLATILE AS 'gp_activate_standby' WITH (OID=5053, DESCRIPTION="Activate a standby");
-
  CREATE FUNCTION gp_request_fts_probe_scan() RETURNS bool LANGUAGE internal VOLATILE AS 'gp_request_fts_probe_scan' EXECUTE ON MASTER WITH (OID=5035, DESCRIPTION="Request a FTS probe scan and wait for response");
 
 

src/include/catalog/pg_proc_gp.h

@@ -22,7 +22,7 @@
 
    WARNING: DO NOT MODIFY THE FOLLOWING SECTION: 
    Generated by catullus.pl version 8
-   on Wed Jan 10 14:47:24 2018
+   on Thu Jan 11 14:21:56 2018
 
    Please make your changes in pg_proc.sql
 */
@@ -725,10 +725,6 @@ DESCR("Perform the catalog operations necessary for adding a new segment");
 DATA(insert OID = 5051 ( gp_remove_segment  PGNSP PGUID 12 1 0 0 f f f f f v 1 0 16 "21" _null_ _null_ _null_ _null_ gp_remove_segment _null_ _null_ _null_ n a ));
 DESCR("Remove a primary segment from the system catalog");
 
-/* gp_activate_standby() => bool */
-DATA(insert OID = 5053 ( gp_activate_standby  PGNSP PGUID 12 1 0 0 f f f f f v 0 0 16 "" _null_ _null_ _null_ _null_ gp_activate_standby _null_ _null_ _null_ n a ));
-DESCR("Activate a standby");
-
 /* gp_request_fts_probe_scan() => bool */
 DATA(insert OID = 5035 ( gp_request_fts_probe_scan  PGNSP PGUID 12 1 0 0 f f f f f v 0 0 16 "" _null_ _null_ _null_ _null_ gp_request_fts_probe_scan _null_ _null_ _null_ n m ));
 DESCR("Request a FTS probe scan and wait for response");

src/include/utils/builtins.h

@@ -1175,7 +1175,7 @@ extern Datum gp_deprecated(PG_FUNCTION_ARGS);
 extern Datum gp_add_master_standby_port(PG_FUNCTION_ARGS);
 extern Datum gp_add_master_standby(PG_FUNCTION_ARGS);
 extern Datum gp_remove_master_standby(PG_FUNCTION_ARGS);
-extern Datum gp_activate_standby(PG_FUNCTION_ARGS);
+extern bool gp_activate_standby(void);
 
 extern Datum gp_add_segment_primary(PG_FUNCTION_ARGS);
 extern Datum gp_add_segment_mirror(PG_FUNCTION_ARGS);

src/test/tinc/tincrepo/mpp/gpdb/tests/storage/walrepl/run/segadmin/ans/add_standby.ans

-set gp_role = utility;
-SET
-select gp_activate_standby();
-psql:/path/sql_file:1: ERROR:  gp_activate_standby can only be run on the standby master (segadmin.c:303)

src/test/tinc/tincrepo/mpp/gpdb/tests/storage/walrepl/run/segadmin/sql/add_standby.sql

--- start_ignore
-SET gp_create_table_random_default_distribution=off;
--- end_ignore
-set gp_role = utility;
-
-select gp_activate_standby();

src/test/tinc/tincrepo/mpp/gpdb/tests/storage/walrepl/run/segadmin/test_query.py

-"""
-Copyright (c) 2004-Present Pivotal Software, Inc.
-
-This program and the accompanying materials are made available under
-the terms of the under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-"""
-
-from tinctest import logger
-from mpp.lib.PSQL import PSQL
-from mpp.models import SQLTestCase
-
-class Segadmin(SQLTestCase):
-    """
-    @gucs gp_create_table_random_default_distribution=off
-    """
-
-    sql_dir = 'sql'
-    ans_dir = 'ans'
-    out_dir = 'output'
-