Message-Id: <5.1.1.6.0.20021119112128.01ab52e0@wolf.csuohio.edu>
Date: Tue, 19 Nov 2002 11:26:15 -0500
To: Stephan Szabo <sszabo@megazone23.bigpanda.com>
From: Ellen Cyran <ellen@urban.csuohio.edu>
Subject: Re: slow group by query
Cc: <pgsql-sql@postgresql.org>
In-Reply-To: <20021119065715.V65980-100000@megazone23.bigpanda.com>
References: <5.1.1.6.0.20021118124632.01b5dcf0@wolf.csuohio.edu>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; format=flowed

I had to modify your query somewhat, but the one below that is pretty much 
the same took
about 12 seconds so once I run it on five years it will take just as 
long.  Thanks for the
suggestion though.

select distinct on (b.msa_code, b.sic, b.own, b.ind_div)
b.msa_code, b.sic, b.own, b.ind_div, y1975.emp from
tbl_bls_msa as b left outer join (select msa_code, sic, own, ind_div, emp 
from tbl_bls_msa as bls
where bls.year='1975' ) as y1975
on (b.msa_code=y1975.msa_code and
b.sic=y1975.sic and b.own=y1975.own and b.ind_div=y1975.ind_div)
where b.msa_code in ('1680', '1640', '0040', '0120', '0080');

I would be interested in knowing more about what postgres extensions are 
available.  Where
are those documented at?


>Have you tried doing the subqueries in from?  Right now you're running
>each subquery once for each output row AFAICS.
>
>Maybe something like (doing only one year for example - and using a
>postgres extension), would work...
>
>select distinct on (b.msa_code, b.sic, b.own, b.ind_div)
>  b.msa_code, b.sic, b.own, b.ind_div, y1975.emp1975 from
>tbl_bls_msa as b left outer join (select emp from tbl_bls_mas as bls
>  where bls.year='1975') y1975 on (b.msa_code=y1975.msa_code and
>  b.sic=y1975.sic and b.own=y1975.own and b.ind_div=y1975.ind_div)
>where msa_code in ('1680', '1640', '0040', '0120', '0080');