Re:

Now i have tried creating the table and the inserting...
The results are the same...
Is it possible that the query planner thinks that is best a sequential scan
when an index on the table is present?
I'm using postgresql 7.1.3 on a redhat 7.1.

Thanks for the help,
Denis

P.S.: I'm sorry having missed the subject of the mail....

At 11.54 24/08/01, Denis Gasparin wrote:
>I have done VACUUM ANALYZE too but the statistics continue preferring
>sequential scan...
>
>Now i'll try to use a different approach:
>- i'll create the empty table with a CREATE TABLE (and a primary key on col1)
>- then i'll populate it using then INSERT..SELECT statement
>- Last i'll check what the statistics say about the SELECT on the primary
>key query.
>
>When i've done, i'll tell you...
>
>Denis
>
>At 19.03 23/08/01, Doug McNaught wrote:
>>Denis Gasparin <denis@edinet.it> writes:
>>
>> > Hi to all!
>> >       I have created a table using the CREATE TABLE new_table
>> > (col1,col2,col3) AS SELECT col1,col2,col3 FROM org_table.
>> >
>> >       I create an index on this table using the statement:
>> > CREATE UNIQUE INDEX table_idx ON new_table (col1).
>> >       Then i do a select as this:
>> > SELECT * FROM new_table WHERE col1 = 'value'.
>> >
>> >       The problem is that when i do an explain this is the query plan:
>> >
>> > Seq Scan on new_table  (cost=0.00..1116.38 rows=500 width=44)>
>> >
>> > Can anyone explain me why it doesn't use the index I have created?
>>
>>How populated is the table?  If it's small, or if you haven't done
>>VACUUM ANALYZE, the statistics may end up preferring a sequential
>>scan.
>>
>>-Doug
>>--
>>Free Dmitry Sklyarov!
>>http://www.freesklyarov.org/
>>
>>We will return to our regularly scheduled signature shortly.
>
>
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