Prevent duplicate call to stored procs

Reuse a CTE for results of call

test/fixtures/privileges.sql

@@ -43,6 +43,7 @@ GRANT INSERT ON TABLE insertonly TO postgrest_test_anonymous;
 GRANT USAGE ON SEQUENCE
       auto_incrementing_pk_id_seq
     , items_id_seq
+    , callcounter_count
 TO postgrest_test_anonymous;
 
 -- Privileges for non anonymous users

test/fixtures/schema.sql

@@ -261,6 +261,18 @@ CREATE FUNCTION sayhello(name text) RETURNS text
 $_$;
 
 
+--
+-- Name: callcounter(); Type: FUNCTION; Schema: test; Owner: -
+--
+
+CREATE SEQUENCE callcounter_count START 1;
+
+CREATE FUNCTION callcounter() RETURNS bigint
+    LANGUAGE sql
+    AS $_$
+    SELECT nextval('test.callcounter_count');
+$_$;
+
 --
 -- Name: test_empty_rowset(); Type: FUNCTION; Schema: test; Owner: -
 --