Fix create_graph failing when ag_catalog is not in search_path (#2505)

create_index_on_column() passed "graphid_ops" as an unqualified operator
class name, so it was resolved against the caller's search_path. Whenever
ag_catalog was not on the search_path, creating a label failed with

  ERROR:  operator class "graphid_ops" does not exist for access method "btree"

even for a fully qualified call such as

  SELECT ag_catalog.create_graph('g');

The error is misleading: the operator class does exist, it is simply not
visible. This affected create_graph(), create_vlabel(), create_elabel(),
the CSV loader, and label creation from a CREATE or MERGE clause at query
time, since all of them reach create_label().

The unqualified name arrived with the id column indexes in #2117, so this
is a regression. Before that commit create_label() built no index and
resolved no name through the search_path. Every other object referenced by
the DDL that create_label() generates is already reached either by OID or
by an ag_catalog qualified name, so qualifying this one restores the
previous behaviour.

Author: NotHimmel

regress/expected/catalog.out

@@ -607,3 +607,55 @@ NOTICE:  graph "graph" has been dropped
 
 (1 row)
 
+--
+-- create_label() must not resolve graphid_ops through the search_path
+--
+-- Every AGE object is referenced with an ag_catalog qualified name here, so
+-- these statements have to work with ag_catalog off the search_path.
+--
+SET search_path TO public;
+SELECT ag_catalog.create_graph('graphid_ops_search_path');
+NOTICE:  graph "graphid_ops_search_path" has been created
+ create_graph 
+--------------
+ 
+(1 row)
+
+-- vertex labels index id, edge labels index start_id and end_id
+SELECT ag_catalog.create_vlabel('graphid_ops_search_path', 'v');
+NOTICE:  VLabel "v" has been created
+ create_vlabel 
+---------------
+ 
+(1 row)
+
+SELECT ag_catalog.create_elabel('graphid_ops_search_path', 'e');
+NOTICE:  ELabel "e" has been created
+ create_elabel 
+---------------
+ 
+(1 row)
+
+-- label creation at query time goes through the same path
+SELECT * FROM ag_catalog.cypher('graphid_ops_search_path',
+    $$CREATE (:query_time_v)-[:query_time_e]->(:query_time_v)$$)
+  AS (result ag_catalog.agtype);
+ result 
+--------
+(0 rows)
+
+SELECT ag_catalog.drop_graph('graphid_ops_search_path', true);
+NOTICE:  drop cascades to 6 other objects
+DETAIL:  drop cascades to table graphid_ops_search_path._ag_label_vertex
+drop cascades to table graphid_ops_search_path._ag_label_edge
+drop cascades to table graphid_ops_search_path.v
+drop cascades to table graphid_ops_search_path.e
+drop cascades to table graphid_ops_search_path.query_time_v
+drop cascades to table graphid_ops_search_path.query_time_e
+NOTICE:  graph "graphid_ops_search_path" has been dropped
+ drop_graph 
+------------
+ 
+(1 row)
+
+SET search_path TO ag_catalog;

regress/sql/catalog.sql

@@ -235,3 +235,21 @@ SELECT count(*) FROM ag_label;
 -- dropping the graphs
 SELECT drop_graph('issue_2245', true);
 SELECT drop_graph('graph', true);
+
+--
+-- create_label() must not resolve graphid_ops through the search_path
+--
+-- Every AGE object is referenced with an ag_catalog qualified name here, so
+-- these statements have to work with ag_catalog off the search_path.
+--
+SET search_path TO public;
+SELECT ag_catalog.create_graph('graphid_ops_search_path');
+-- vertex labels index id, edge labels index start_id and end_id
+SELECT ag_catalog.create_vlabel('graphid_ops_search_path', 'v');
+SELECT ag_catalog.create_elabel('graphid_ops_search_path', 'e');
+-- label creation at query time goes through the same path
+SELECT * FROM ag_catalog.cypher('graphid_ops_search_path',
+    $$CREATE (:query_time_v)-[:query_time_e]->(:query_time_v)$$)
+  AS (result ag_catalog.agtype);
+SELECT ag_catalog.drop_graph('graphid_ops_search_path', true);
+SET search_path TO ag_catalog;

src/backend/commands/label_commands.c

@@ -509,7 +509,8 @@ static void create_index_on_column(char *schema_name,
     index_col->expr = NULL;
     index_col->indexcolname = NULL;
     index_col->collation = NIL;
-    index_col->opclass = list_make1(makeString("graphid_ops"));
+    index_col->opclass = list_make2(makeString("ag_catalog"),
+                                    makeString("graphid_ops"));
     index_col->opclassopts = NIL;
     index_col->ordering = SORTBY_DEFAULT;
     index_col->nulls_ordering = SORTBY_NULLS_DEFAULT;