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
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