Each function performs the visibility check for one type of database
object. Note that <function>pg_table_is_visible</function> can also be used
with views, materialized views, indexes, sequences and foreign tables;
+ <function>pg_function_is_visible</function> can also be used with
+ procedures and aggregates;
<function>pg_type_is_visible</function> can also be used with domains.
For functions and operators, an object in
the search path is visible if there is no object of the same name