adding _OBS_GetRelatedColumn function

src/pg/sql/40_observatory_utility.sql

@@ -151,3 +151,25 @@ BEGIN
 
 END;
 $$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION cdb_observatory._GetRelatedColumn(columns_ids text[], reltype text )
+RETURNS TEXT[]
+AS $$
+DECLARE
+  result TEXT[];
+BEGIN
+  EXECUTE '
+    With ids as (
+      select row_number() over() as no, id from (select unnest($1) as id) t
+    )
+    select array_agg(target_id order by no)
+    FROM  ids
+    LEFT JOIN observatory.obs_column_to_column
+    on  source_id  = id
+    where reltype = $2 or reltype is null
+  '
+  INTO result
+  using columns_ids, reltype;
+  return result;
+END;
+$$ LANGUAGE plpgsql;