Re: Queries not using Index

>On Tue, 23 Jul 2002, Daryl Herzmann wrote:
>
>> snet=# explain analyze select * from t2002_06 WHERE station = 'SAMI4';
>> NOTICE: QUERY PLAN:
>>
>> Seq Scan on t2002_06 (cost=0.00..35379.69 rows=34979 width=47) (actual
>> time=67.89..3734.93 rows=38146 loops=1)
>> Total runtime: 3748.33 msec
>>
>> EXPLAIN
>>
>> snet=# set enable_seqscan=off;
>> SET VARIABLE
>> snet=# explain analyze select * from t2002_06 WHERE station = 'SAMI4';
>> NOTICE: QUERY PLAN:
>>
>> Index Scan using t2002_06_station_idx on t2002_06 (cost=0.00..132124.96
>> rows=34979 width=47) (actual time=72.03..298.85 rows=38146 loops=1)
>> Total runtime: 317.76 msec
>
>Looks like the estimated cost is way divorced from reality. Is the
>34979 row estimate even realistic and how well ordered is the table
>(actually output from pg_statistic would be good as well :) ).

Thanks for the help! I am not sure if I can answer your questions. I will
try :)

I believe the row estimate is realistic based on this value.

snet=# select count(*) from t2002_06 WHERE station = 'SAMI4';
count
-------
38146

I am really sorry, but I don't know what to output from pg_statistic. I
searched around on the Internet and was not sure what to send you from
this table. Sorry :(

Thanks!
Daryl