Richard,
thanks for the reply. I actually did what you suggested but still the
same. Now i set ENABLE_SEQSCAN=false in the perl script which works but
I dont think thats the way it shold be done.
Alex
Richard Huxton wrote:
> Alex wrote:
>
>> Hi,
>> I have a query that runs pretty slow and tried to use explain to see
>> where the problem is.
>> Both tables have 2.1 and 2.8 million records.
>>
>> In the Explain output I see that a Seq Scan is used on nval_price_hist
>> what I dont quite understand.
>> Could some one help me creating the correct indices?
>
>
> Hmm - it knows there are 2 million rows (2116900) in nval_price_hist
> and yet it isn't using the index on price_id even though it's
> expecting a small number of rows (53) to come out of the join.
>
>> SELECT ..........
>> FROM price_hist AS P, nval_price_hist AS N
>> WHERE P.price_id = N.price_id AND P.sec_code = 512084 AND P.eval_date =
>> '2004-10-15' ;
>>
>> Hash Join (cost=210.16..61370.19 rows=53 width=602)
>> Hash Cond: ("outer".price_id = "inner".price_id)
>> -> Seq Scan on nval_price_hist n (cost=0.00..50575.00 rows=2116900
>
> ...
>
> 1. VACUUM FULL ANALYSE the two tables.
> 2. Re-run the query with EXPLAIN ANALYSE instead of just EXPLAIN
> 3. SET ENABLE_SEQSCAN=false; then re-run step 2
>
> That will ensure the statistics are up-to-date, show the actual costs
> as well as the expected costs and finally let us compare the index
> against a sequential scan.
> --
> Richard Huxton
> Archonet Ltd
>
> ---------------------------(end of broadcast)---------------------------
> TIP 8: explain analyze is your friend
>
>
