[Feature] Try to use tableoid in order to distinguish records on table inheritance

[crashtech]

Since the column tableoid is available without the need of extra join or anything, it seems to be faster to use it as the source of inherited table discover.

We already use the tableoid as a join to pg_class.oid to get the table name, but maybe we can do it directly and use the number as the reference. This can also facilitate many other mappings for inheritance.

[crashtech]

Try to use type map!