Preserve pg_catalog at end of search path if it is the case to allow

pg_catalog overloaded function to be executed.
Add regression test on search_path forcing.

Author: darold

Makefile

@@ -21,7 +21,7 @@ TESTS        = 00_init 01_oncommitdelete 02_oncommitpreserve \
 	       03_createontruncate 04_rename 05_useindex \
 	       06_createas 07_createlike 08_plplgsql \
 	       09_transaction 10_foreignkey 11_after_error \
-	       12_droptable
+	       12_droptable 13_searchpath
 
 REGRESS      = $(patsubst test/sql/%.sql,%,$(TESTS))
 REGRESS_OPTS = --inputdir=test

test/expected/13_searchpath.out

@@ -0,0 +1,43 @@
+----
+-- Regression test to Global Temporary Table implementation
+--
+-- Test on search_path forced by the extension
+--
+----
+SHOW search_path ;
+         search_path          
+------------------------------
+ "$user", public, pgtt_schema
+(1 row)
+
+create schema first_schema;
+create schema second_schema;
+SET search_path TO "$user", public, fisrt_schema, second_schema,pg_catalog;
+SHOW search_path ;
+                              search_path                              
+-----------------------------------------------------------------------
+ "$user", public, fisrt_schema, second_schema, pg_catalog, pgtt_schema
+(1 row)
+
+CREATE EXTENSION pgtt;
+ERROR:  extension "pgtt" already exists
+SHOW search_path ;
+                              search_path                              
+-----------------------------------------------------------------------
+ "$user", public, fisrt_schema, second_schema, pg_catalog, pgtt_schema
+(1 row)
+
+SET search_path TO pg_catalog;
+SHOW search_path ;
+       search_path       
+-------------------------
+ pg_catalog, pgtt_schema
+(1 row)
+
+SET search_path TO public;
+SHOW search_path ;
+     search_path     
+---------------------
+ public, pgtt_schema
+(1 row)
+

test/sql/13_searchpath.sql

@@ -0,0 +1,19 @@
+----
+-- Regression test to Global Temporary Table implementation
+--
+-- Test on search_path forced by the extension
+--
+----
+
+
+SHOW search_path ;
+create schema first_schema;
+create schema second_schema;
+SET search_path TO "$user", public, fisrt_schema, second_schema,pg_catalog;
+SHOW search_path ;
+CREATE EXTENSION pgtt;
+SHOW search_path ;
+SET search_path TO pg_catalog;
+SHOW search_path ;
+SET search_path TO public;
+SHOW search_path ;