| From: | Michael Fuhr <mike(at)fuhr(dot)org> |
|---|---|
| To: | Paul Tillotson <spam1011(at)adelphia(dot)net> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: IN subquery not using a hash |
| Date: | 2005-07-21 01:03:28 |
| Message-ID: | 20050721010328.GA46682@winnie.fuhr.org |
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| Thread: | |
| Lists: | pgsql-general |
On Wed, Jul 20, 2005 at 08:11:46PM -0400, Paul Tillotson wrote:
> Tom Lane wrote:
> >Hardly likely, considering it's estimating only 296 rows in the subquery
> >output. My bet is that you've chosen a datatype whose comparisons are
> >not hashable (like char(n)). What is the datatype of parentid in these
> >tables, anyway?
> >
> I don't have access to the machine now, but my memory is that
> parent.parentid is numeric(10,2) and child.parentid is int.
Numeric isn't hashable, but I don't know enough about the internals
to say why. Tom?
Why different types, and why numeric for one of them? Why not
integer for both?
--
Michael Fuhr
http://www.fuhr.org/~mfuhr/
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