To: Ben <midfield@gmail.com>
cc: pgsql-performance@postgresql.org
Subject: Re: encourging bitmap AND 
In-reply-to: <5297F6A0-AB39-49F1-80BB-8EE60F3E243E@gmail.com> 
References: <5297F6A0-AB39-49F1-80BB-8EE60F3E243E@gmail.com>
Comments: In-reply-to Ben <midfield@gmail.com>
	message dated "Thu, 23 Dec 2010 12:06:40 -0800"
Date: Thu, 23 Dec 2010 15:52:12 -0500
Message-ID: <27812.1293137532@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

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.

			regards, tom lane