Re: Performance problems, bad estimates and plan

Allan Wang <allanvv@gmail.com> writes:
> It seems that Postgres is estimating that all rows in a 50k row table
> will be returned, but only one should match.

I think this is the same issue fixed here:

2005-04-03 21:43  tgl

    * src/backend/optimizer/path/: costsize.c (REL7_4_STABLE),
    costsize.c (REL8_0_STABLE), costsize.c: In cost_mergejoin, the
    early-exit effect should not apply to the outer side of an outer
    join.  Per andrew@supernews.

Are you running 7.4.8 or 8.0.2 or later?

            regards, tom lane