SELECT pgperf._check_table_or_view('pg_database');
 _check_table_or_view 
----------------------
 t
(1 row)

SELECT pgperf._check_table_or_view('pg_stat_activity');
 _check_table_or_view 
----------------------
 t
(1 row)

SELECT pgperf._check_table_or_view('nosuchtableorview');
 _check_table_or_view 
----------------------
 f
(1 row)