Re: SQL/MED - core functionality

On Wed, 2010-12-22 at 07:36 -0800, David Fetter wrote:
> > 
> > > > 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.
> 
> 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.

A fairly gross estimate will be all that is required.

Without it, we'd better be looking at some advanced query-cancel
support, cos the "17 hours and still going" events of previous SQL
gateway products seems to be looming in my rear view mirror.

-- Simon Riggs           http://www.2ndQuadrant.com/books/PostgreSQL Development, 24x7 Support, Training and Services