RE: Sort

Here is the query:

SELECT Impression.AdNumber_AdNum,
    Impression.Webmaster_WebmasterNum,
    Impression.Banner_BannerNum, COUNT(Click.ClickNum)
    AS ClickCount
FROM Impression INNER JOIN
    Click ON
    Impression.ImpressionNum = Click.Impression_ImpressionNum
GROUP BY Impression.AdNumber_AdNum,
    Impression.Webmaster_WebmasterNum,
    Impression.Banner_BannerNum

-----------------
Nathan Barnett

-----Original Message-----
From: pgsql-general-owner@hub.org [mailto:pgsql-general-owner@hub.org]On
Behalf Of Mitch Vincent
Sent: Friday, July 21, 2000 2:48 PM
To: Nathan Barnett; pgsql-general@postgresql.org
Subject: Re: [GENERAL] Sort


Show the query and maybe someone could help :-)

----- Original Message -----
From: "Nathan Barnett" <nbarnett@cellularphones.com>
To: <pgsql-general@postgresql.org>
Sent: Friday, July 21, 2000 2:33 PM
Subject: [GENERAL] Sort


> I'm currently using v7.0.2 of PostgreSQL.
>
> I have a query that performs a group by on three columns.  The EXPLAIN of
> the query is as follows:
>
> Aggregate  (cost=4116.05..4125.47 rows=94 width=24)
>   ->  Group  (cost=4116.05..4123.12 rows=942 width=24)
>         ->  Sort  (cost=4116.05..4116.05 rows=942 width=24)
>               ->  Nested Loop  (cost=0.00..4069.52 rows=942 width=24)
>                     ->  Seq Scan on click  (cost=0.00..15.42 rows=942
> width=8)
>                     ->  Index Scan using impression_pkey on impression
> (cost=0.00..4.29 rows=1 width=16)
>
> I need to speed up this query.  I have already created an index on the
three
> columns query_idx(columna, columnb,columnc).  Is there some other index
that
> I could add which would speed up the query.  There is a high frequency in
> the table of each group.  Each group probably makes up 10% of the table.
> Does this force a sequence scan when sorting and grouping?  Basically just
> looking for suggestions.
>
>
> ----------------
> Nathan Barnett
>
>