Re: database not using indexes, yet

On postgres 8.3.11 on linux centos 5 we have a table  not too big  with primary key index on

Indexes:
   "aida_references_pkey" PRIMARY KEY, btree (aida_reference_id)

the query not use index:

aidadb=#  explain analyze select aida_reference_id from aida.aida_references where aida_reference_id = '3145';
                                                  QUERY PLAN
----------------------------------------------------------------------------------------------------------------
 Seq Scan on aida_references  (cost=0.00..51489.15 rows=1 width=4) (actual time=0.173..1457.643 rows=1 loops=1)
  Filter: (aida_reference_id = 3145)
 Total runtime: 1457.696 ms


already executed the vacuum ,reindex.

Please help

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Silvio Brandani