Supportin PostgreSQL OID casts

[Muhammad Gelbana]

I'm willing to implement running PostgreSQL queries involving OID casts

*For example:*
SELECT * FROM pg_attribute
WHERE attrelid = 'mytable'::regclass;

*Should be executed as:*
SELECT * FROM pg_attribute
WHERE attrelid = (SELECT oid FROM pg_class WHERE relname = 'mytable');

Note that *reglass* maps to the *pg_class* table.

What is the "calcite way" to implement this ? Should I write a rule ?
Or should I rewrite the query before implementing it (I'm not sure where is
that) ?

Thanks,
Gelbana