7.3.1 index use / performance

Hi,

i am just in the stage of having migrated my test system to 7.3.1
and i am experiencing some performance problems.

i have a table "noon"
Table "public.noon"
Column | Type | Modifiers
------------------------+------------------------+-----------
v_code | character varying(4) |
log_no | bigint |
report_date | date |
report_time | time without time zone |
voyage_no | integer |
charterer | character varying(12) |
port | character varying(24) |
duration | character varying(4) |
rotation | character varying(9) |
......

with a total of 278 columns.

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)

On the test 7.3.1 system (a FreeBSD 4.7-RELEASE-p2, Celeron 1.2GHz
400Mb, with 168Mb for pgsql),
i get:
dynacom=# EXPLAIN ANALYZE select
FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where
v_code='4500' and rotation='NOON ' and report_date between
'2002-01-07' and '2003-01-07';
QUERY PLAN

-------------------------------------------------------------------------------------------------------------------
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)

after i drop the noonf_date index i actually get better performance
cause the backend uses now the more appropriate index noonf_vcode :

dynacom=# EXPLAIN ANALYZE select
FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where
v_code='4500' and rotation='NOON ' and report_date between
'2002-01-07' and '2003-01-07';
QUERY PLAN

-----------------------------------------------------------------------------------------------------------------------------------------
Index Scan using noonf_vcode on noon (cost=0.00..3122.88 rows=1
width=39) (actual time=0.16..13.92 rows=259 loops=1)
Index Cond: (v_code = '4500'::character varying)
Filter: ((rotation = 'NOON '::character varying) AND (report_date
>= '2002-01-07'::date) AND (report_date <= '2003-01-07'::date))
Total runtime: 14.98 msec
(4 rows)

On the pgsql 7.2.3 development system (a RH linux 2.4.7, PIII 1 GHz,
1Mb, with 168M for pgsql), i always get the right index use:

dynacom=# EXPLAIN ANALYZE select
FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where
v_code='4500' and rotation='NOON ' and report_date between
'2002-01-07' and '2003-01-07';
NOTICE: QUERY PLAN:

Index Scan using noonf_vcode on noon (cost=0.00..3046.38 rows=39
width=39) (actual time=0.09..8.55 rows=259 loops=1)
Total runtime: 8.86 msec

EXPLAIN

Is something i am missing??
Is this reasonable behaviour??

P.S.
Yes i have vaccumed analyzed both systems before the queries were issued.
==================================================================
Achilleus Mantzios
S/W Engineer
IT dept
Dynacom Tankers Mngmt
Nikis 4, Glyfada
Athens 16610
Greece
tel: +30-10-8981112
fax: +30-10-8981877
email: achill(at)matrix(dot)gatewaynet(dot)com
mantzios(at)softlab(dot)ece(dot)ntua(dot)gr