| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
| Cc: | Shigeru HANADA <hanada(at)metrosystems(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: SQL/MED - core functionality |
| Date: | 2010-12-22 15:00:16 |
| Message-ID: | 1293030016.1193.28081.camel@ebony |
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| Thread: | |
| Lists: | pgsql-hackers |
On Wed, 2010-12-22 at 09:03 -0500, Andrew Dunstan wrote:
> Answering a few of your questions
Many thanks.
> > 7. Why does ANALYZE skip foreign tables? Surely its really important we
> > know things about a foreign table, otherwise we are going to optimize
> > things very badly.
>
> Quite apart from other reasons, such as possible ephemerality of the
> data, the difficulty of taking a reasonable random sample from an
> arbitrary foreign data source seems substantial, and we surely don't
> want ANALYSE to have to run a full sequential scan of a foreign data source.
I think we need something that estimates the size of a table, at least,
otherwise queries will be completely un-optimised.
> > 10. Can a foreign table be referenced by a FK?
>
> I don't see how it can be. There would be no unique index to use.
That answers another question also.
Still many unanswered.
--
Simon Riggs http://www.2ndQuadrant.com/books/
PostgreSQL Development, 24x7 Support, Training and Services
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