Re: Query optimization using order by and limit

On Wed, Sep 21, 2011 at 11:22:53PM -0400, Tom Lane wrote:
> Michael Viscuso <michael.viscuso@getcarbonblack.com> writes:
> > Greg/Tom, you are correct, these columns should be modified to whatever
> > is easiest for Postgres to recognize 64-bit unsigned integers.  Would
> > you still recommend bigint for unsigned integers?  I likely read the
> > wrong documentation that suggested bigint for signed 64-bit integers and
> > numeric(20) for unsigned 64-bit integers.
>
> Unsigned?  Oh, hm, that's a bit of a problem because we don't have any
> unsigned types.  If you really need to go to 2^64 and not 2^63 then
> you're stuck with numeric ... but that last bit is costing ya a lot.
>
>             regards, tom lane
>

Hi Michael,

If you have access to the application, you can map the unsigned 64-bits
to the PostgreSQL signed 64-bit type with a simple subtraction. That will
allow you to drop all the numeric use. Also if the guid is a 64-bit
values stuffed into a numeric(20), you can do it there as well. I achieved
a hefty performance boost by making those application level changes in a
similar situation.

Regards,
Ken