Re: Surprise :-(

PG7.1.3 on RH7.1 on Dell PowerEdge 2500SC P3-933, 1GB RAM, 18GB SCSI160
There are 350k rows with trxtype=MP
With indexscan=off:
Aggregate  (cost=22975.15..22990.27 rows=302 width=24)
  ->  Group  (cost=22975.15..22982.71 rows=3025 width=24)
        ->  Sort  (cost=22975.15..22975.15 rows=3025 width=24)
              ->  Seq Scan on tbas_transactions  (cost=0.00..22800.29
rows=3025 width=24)
Time: 25.9s
With indexscan=on:
Aggregate  (cost=10874.64..10889.76 rows=302 width=24)
  ->  Group  (cost=10874.64..10882.20 rows=3025 width=24)
        ->  Sort  (cost=10874.64..10874.64 rows=3025 width=24)
              ->  Index Scan using trx_trxtype_idx on tbas_transactions
(cost=0.00..10699.78 rows=3025 width=24)
Time: 24.9s
The point is I need to run this query in a fraction of the above time,
otherwise I'm in deep trouble.
Any suggestion is welcome.

-----Original Message-----
From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Mihai Gheorghiu <tanethq@earthlink.net>
Cc: pgsql-general@postgresql.org <pgsql-general@postgresql.org>
Date: Thursday, September 05, 2002 6:51 PM
Subject: Re: [GENERAL] Surprise :-(


>
>On Thu, 5 Sep 2002, Mihai Gheorghiu wrote:
>
>>
>> explain select account, sum(amount) from tbas_transactions where isposted
>> and trxtype = 'MP' group by account;
>> psql:xx.txt:1: NOTICE:  QUERY PLAN:
>>
>> Aggregate  (cost=10874.64..10889.76 rows=302 width=24)
>>   ->  Group  (cost=10874.64..10882.20 rows=3025 width=24)
>>         ->  Sort  (cost=10874.64..10874.64 rows=3025 width=24)
>>               ->  Index Scan using trx_trxtype_idx on tbas_transactions
>> (cost=0.00..10699.78 rows=3025 width=24)
>>
>> EXPLAIN
>>
>> Sorry, I do not have an explain from before vacuum analyze.
>> The table has ~700k rows and indices on account, trxtype and a few other
>> fields used in other queries.
>
>If you set enable_indexscan=off; and then run explain/run the query
>is it better?
>
>For other questions, how many rows have trxtype='MP' really and what
>version are you running?
>
>