Display empty schemas on the sidebar (#621)

* Display empty schemas on the sidebar
* Add schemas fetching test
* Skip pg_temp schemas
* Exclude pg_temp tables from other queries

pkg/statements/sql/objects.sql

@@ -20,7 +20,7 @@ WITH all_objects AS (
     pg_catalog.pg_namespace n ON n.oid = c.relnamespace
   WHERE
     c.relkind IN ('r','v','m','S','s','')
-    AND n.nspname !~ '^pg_toast'
+    AND n.nspname !~ '^pg_(toast|temp)'
     AND n.nspname NOT IN ('information_schema', 'pg_catalog')
     AND has_schema_privilege(n.nspname, 'USAGE')
 
@@ -38,7 +38,7 @@ WITH all_objects AS (
   JOIN
     pg_catalog.pg_proc p ON p.pronamespace = n.oid
   WHERE
-    n.nspname !~ '^pg_toast'
+    n.nspname !~ '^pg_(toast|temp)'
     AND n.nspname NOT IN ('information_schema', 'pg_catalog')
 )
 SELECT * FROM all_objects

pkg/statements/sql/schemas.sql

@@ -2,5 +2,8 @@ SELECT
   schema_name
 FROM
   information_schema.schemata
+WHERE
+  schema_name NOT IN ('information_schema', 'pg_catalog')
+  AND schema_name !~ '^pg_(toast|temp)'
 ORDER BY
   schema_name ASC