Re: encourging bitmap AND

On Dec 23, 2010, at 12:52 PM, Tom Lane wrote:

> Ben <midfield@gmail.com> writes:
>> i have a schema similar to the following
>
>> create index foo_s_idx on foo using btree (s);
>> create index foo_e_idx on foo using btree (e);
>
>> i want to do queries like
>
>> select * from foo where 150 between s and e;
>
> That index structure is really entirely unsuited to what you want to do,
> so it's not surprising that the planner isn't impressed with the idea of
> a bitmap AND.
>
> I'd suggest setting up something involving a gist index over an
> interval-ish datatype.  The PERIOD datatype that Jeff Davis is fooling
> with would do what you want --- see
>     http://pgfoundry.org/projects/temporal
>     http://thoughts.j-davis.com/2009/11/08/temporal-keys-part-2/
> If you don't want any add-on parts involved, you could fake it by using
> a box or possibly lseg.

Thanks for the quick response.  I've already played a lot with the PERIOD datatype and GIST, it works pretty good, but
Ifound that the lack of statistics and real selectivity functions hurt me.  I was experimenting with the two column
setupas an alternative, but if you think this is a dead end I'll look elsewhere. 

Best regards, Ben