Re: PGSQL internals question...

Tom Lane wrote:

> It's not clear to me why you think that ExecProject has anything to
> do with the problem... 

Only that it calls things like ExecEvalExpr which evaluates different
types of column expressions. I was thinking I would need a T_classoid,
or T_magicColumn expression type evaluated there which grabs the
classoid from somewhere.

> I doubt that routine will change at all.
> I'd be inclined to look at the handling of "system" attributes such
> as OID. 

Except that oid really exists in the db right? The only thing special
about oid compared to any other attribute is that it isn't expanded by
"*", which doesn't seem like that much difference.

> Probably you'd need to add a source-table-OID field to
> HeapTupleData, which XXXScan would need to fill in, 

Wouldn't ExecTargetList need access to this HeapTupleData instance? Does
it?

> and then there's
> have to be code to pull it out again when the right system attribute
> number is referenced.

Would a non-existant attribute have a system attribute number? Where do
you suggest this code should be that "pulls it out"?