On 05.10.2010 17:56, Robert Haas wrote:
On Tue, Oct 5, 2010 at 10:41 AM, Tom Lane<t...@sss.pgh.pa.us> wrote:
(I'd also say that your performance estimate is miles in advance of any
facts; but even if it's true, the caching ought to be inside the FDW,
because we have no clear idea of what it will need to cache.)
I can't imagine how an FDW could possibly be expected to perform well
without some persistent local data storage. Even assume the remote
end is PG. To return a cost, it's going to need the contents of
pg_statistic cached locally, for each remote table. Do you really
think it's going to work to incur that overhead once per table per
backend startup?
It doesn't seem completely out of the question to me. Sure, it's
expensive, but it's only incurred the first time a remote table is
accessed in a session. Local persistent storage would be nice, but a lot
of applications might prefer to not use it anyway, to ensure that fresh
statistics are used.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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