Meta info for queries

Hi all,

I would like to write an table and query editor for Posgresql la pgAccess.
But I would need some help from postgresql to make it work smarter.

Are there functions / switches to get the following information:
* Effective Tables included in the query (a query could call views or stored
procedures or whatever so I need info after Postgresql Rewrite unit has done
its job)
* Effective fields, that is source table and field for each of the output
fields. Columns calculated from functions should not specify this or make it
clear that this is not a direct output.
* Return all oids, although not explicitly specified in queries.
* The same for xmin (row versioning)

In MS-Access:
* primary keys are used to access rows in tables and queries
* There is an internal row versioning.
* Processes Joins in the ODBC layer, i.e., does only query tables and joins
the results at the client.

Thanx, Erny