| From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
|---|---|
| To: | David Fetter <david(at)fetter(dot)org> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Shigeru HANADA <hanada(at)metrosystems(dot)co(dot)jp>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: SQL/MED - core functionality |
| Date: | 2010-12-22 15:54:06 |
| Message-ID: | 1293033164-sup-7847@alvh.no-ip.org |
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| Lists: | pgsql-hackers |
Excerpts from David Fetter's message of mié dic 22 12:36:10 -0300 2010:
> On Wed, Dec 22, 2010 at 03:00:16PM +0000, Simon Riggs wrote:
> > On Wed, 2010-12-22 at 09:03 -0500, Andrew Dunstan wrote:
> > > 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.
>
> The estimated size for a lot of things--streams of data, for
> example--is infinity. I suppose that's a good default for some cases.
Since we don't have streaming queries, this would seem rather pointless ...
Surely the FDW must be able to limit the resultset somehow.
--
Álvaro Herrera <alvherre(at)commandprompt(dot)com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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