Re: patch: SQL/MED(FDW) DDL

On 09/28/10 17:26, Robert Haas wrote:
> First, it seems totally wrong to assume that the same functions and
> operators will be defined on the remote side as you have locally;
> indeed, for CSV files, you won't have anything defined on the remote
> side at all.  You need some kind of a discovery mechanism here to
> figure out which quals are push-downable.  And it should probably be
> something generic, not a bunch of hard-wired rules that may or may not
> be correct in any particular case.  What if the remote side is a
> competing database product that doesn't understand X = ANY(Y)?
> Second, even if a functions or operators does exist on both sides of
> the link, how do you know whether they have compatible semantics?

Or side-effects.

The SQL/MED specification has "routine mappings" for this purpose. We 
will need that or something similar.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com