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Date: Tue, 07 Jan 2003 13:00:12 +0100
From: Tomasz Myrta <jasiek@klaster.net>
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To: Achilleus Mantzios <achill@matrix.gatewaynet.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: [SQL] 7.3.1 index use / performance
References: <Pine.LNX.4.44.0301071338480.7770-100000@matrix.gatewaynet.com>
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Achilleus Mantzios wrote:
<cut>

 > it has indexes:
 > Indexes: noonf_date btree (report_date),
 >          noonf_logno btree (log_no),
 >          noonf_rotation btree (rotation text_ops),
 >          noonf_vcode btree (v_code),
 >          noonf_voyageno btree (voyage_no)
 >
<cut>

 >
 > 
-------------------------------------------------------------------------------------------------------------------
 >  Index Scan using noonf_date on noon  (cost=0.00..4.46 rows=1 width=39)
 > (actual time=0.27..52.89 rows=259 loops=1)
 >    Index Cond: ((report_date >= '2002-01-07'::date) AND (report_date <=
 > '2003-01-07'::date))
 >    Filter: ((v_code = '4500'::character varying) AND (rotation = 'NOON
 > '::character varying))
 >  Total runtime: 53.98 msec
 > (4 rows)
<cut>

Maybe it is not an answer to your question, but why don't you help 
Postgres by yourself?
For this kind of queries it's better to drop index on report_date - your 
report period is one year and answer to this condition is 10% records (I 
suppose)
It would be better to change 2 indexes on v_code and rotation into one 
index based on both fields.
What kind of queries do you have? How many records returns each "where" 
condition? Use indexes on fields, on which condition result in smallest 
amount of rows.

Regards,
Tomasz Myrta