Re: Bad planner decision in Postgres

> Matthew Wakeling <mnw21@cam.ac.uk> writes:
> > [ snip... ]
> > If we remove the limit, then the planner switches to this query plan:
>
> > Limit  (cost=156.24..156.26 rows=10 width=14)
>
> ... which still has a limit.  I think you have made several cut-and-paste
> errors here, because the plans you are exhibiting aren't legal for the
> queries you say they are for.  Nor do I see a reason that the planner
> would use, eg, a Sort step for a query with no ORDER BY.  Have you
> perhaps been fooling with the various enable_xxx options to try to force
> the planner to do what you think it should do?

I'm sorry, yes they are cut-and-paste errors. I haven't fiddled with the
enable_xxx options to get those results. The queries that I ran actually
did have an order by clause (ordered on column), and that query you point
out as having a limit is another copy-and-paste error - I used a limit
with a large offset, which has an identical performance characteristic as
having no limit.

The problem stands, my copy-and-paste sucked.

Matthew

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