Re: query planner weirdness?

2008/6/28 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:

> "Bob Duffey" <bobduffey68(at)gmail(dot)com> writes:
> > I'm seeing some query plans that I'm not expecting. The table in
> question
> > is reasonably big (130,000,000 rows). The table has a primary key,
> indexed
> > by one field ("ID", of type bigint). Thus, I would expect the following
> > query to simply scan through the table using the primary key:
>
> > select * from "T" order by "ID"
>
> This is not wrong, or at least not obviously wrong. A full-table
> indexscan is often slower than seqscan-and-sort. If the particular
> case is wrong for you, you need to look at adjusting the planner's
> cost parameters to match your environment. But you didn't provide any
> evidence that the chosen plan is actually worse than the alternative ...
>

Hi Tom,

Thanks for the reply. Is there some way I can provide evidence of the
alternative being slower/faster? I guess that's my intuition, but since I
can't figure out how to get postgres to use the alternative as the query
plan, I can't test if it's slower!

Bob