Re: Index not used in query. Why? - Mailing list pgsql-performance

There's a chance that you could gain from quoting the '4' and '6' if
those orders.id_status isn't a pure int column and is indexed.

See http://www.postgresql.org/docs/7.4/static/datatype.html#DATATYPE-INT

-tfo

--
Thomas F. O'Connell
Co-Founder, Information Architect
Sitening, LLC
http://www.sitening.com/
110 30th Avenue North, Suite 6
Nashville, TN 37203-6320
615-260-0005

On Oct 19, 2004, at 12:49 PM, Contact AR-SD.NET wrote:

> Is there a solution to make it faster?
> At the end I need only in the query the id_status =4 and 6, but if I
> write
> in the sql query (where condition) where id_status in (4,6), the
> explain
> says the same(the slow version).
>
> For example:
> SELECT count(o.id)  FROM orders o
>                                    INNER JOIN report r ON
> o.id=r.id_order
>                                    INNER JOIN status s ON
> o.id_status=s.id
>                                    INNER JOIN contact c ON o.id_ag=c.id
>                                    INNER JOIN endkunde e ON
> o.id_endkunde=e.id
>                                    INNER JOIN zufriden z ON
> r.id_zufriden=z.id
>                                    INNER JOIN plannung v ON
> v.id=o.id_plannung
>                                    INNER JOIN mpsworker w ON
> v.id_worker=w.id
>                                    INNER JOIN person p ON p.id =
> w.id_person
>                                    WHERE o.id_status in (4,6);
>
> The result for this query is also without index searches.
>
> I really have to make this query a little more faster. Suggestions?
>
> Regards,
> Andy.
>
> ----- Original Message -----
> From: "Tom Lane" <tgl@sss.pgh.pa.us>
> To: "Andrei Bintintan" <klodoma@ar-sd.net>
> Cc: <pgsql-performance@postgresql.org>
> Sent: Tuesday, October 19, 2004 7:52 PM
> Subject: Re: [PERFORM] Index not used in query. Why?
>
>
>> "Andrei Bintintan" <klodoma@ar-sd.net> writes:
>>> Hi to all! I have the following query. The execution time is very
>>> big,
> it
>>> doesn't use the indexes and I don't understand why...
>>
>> Indexes are not necessarily the best way to do a large join.
>>
>>> If I use the following query the indexes are used:
>>
>> The key reason this wins seems to be that the id_status = 4 condition
>> is far more selective than id_status > 3 (the estimates are 52 and
>> 36967
>> rows respectively ... is that accurate?) which means that the second
>> query is inherently about 1/700th as much work.  This, and not the use
>> of indexes, is the fundamental reason why it's faster.
>>
>> regards, tom lane
>>
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