Indices are not used by the optimizer

Hello all!

On PostgreSQL V7.3.2 on TRU64 I have a table
and applied indices for that table.
But on a simple query the indices are not used by the optimizer.
(An sequential scan is used which takes a lot of time)
I have done
VACUUM and VACUUM analyze
but without any change to the optimizer.

Can someone give me a hint what I should do to give the
optimizer a start?
--------------------------------------

Well, let's start by the query

wetter=# explain select * from wetter where epoche > '2001-01-01';                               QUERY PLAN
------------------------------------------------------------------------- Seq Scan on wetter  (cost=0.00..614795.55
rows=19054156width=16)   Filter: (epoche > '2001-01-01 00:00:00+00'::timestamp with time zone)
 
(2 rows)

wetter=#


The table definition is as follows: \d wetter              Table "public.wetter"  Column   |           Type           |
Modifiers
-----------+--------------------------+----------- sensor_id | integer                  | not null epoche    |
timestampwith time zone | not null wert      | real                     | not null
 
Indexes: wetter_pkey primary key btree (sensor_id, epoche),         wetter_epoche_idx btree (epoche),
wetter_sensor_id_idxbtree (sensor_id)
 
Triggers: RI_ConstraintTrigger_45702811,          t_ins_wetter_wetterakt

wetter=#


The trigger information is as follows:
select * from pg_trigger where tgname='RI_ConstraintTrigger_45702811'; tgrelid  |            tgname             |
tgfoid| tgtype | tgenabled 
 
| tgisconstraint | tgconstrname | tgconstrrelid | tgdeferrable | 
tginitdeferred | tgnargs | tgattr |    tgargs

----------+-------------------------------+--------+--------+-----------+----------------+--------------+---------------+--------------+----------------+---------+--------+---------------------------------------------------------------------------------------
43169106| RI_ConstraintTrigger_45702811 |   1644 |     21 | t  | t              | <unnamed>    |      43169098 | f
     | f           |       6 |        | 
 
<unnamed>\000wetter\000sensoren_an_orten\000UNSPECIFIED\000sensor_id\000sensor_id\000
(1 row)

wetter=#


and t_ins_wetter_wetterakt
is a PLPGSQL Funktion which copies some information into another table
when an insert or update is done.


-- 

Mit freundlichen Gruessen / With best regards   Reiner Dassing