Re: Question about indexing!

pgsql_bbs table has about 15,000 rows!
And almost of them are satify (topic='qna' and deleted<2) condition.

This explain result have a large cost.
I want to low this query cost.

Thanks for your concern :-)

>> select * from pgsql_bbs where topic = 'qna' and deleted < 2
>>        order by gid desc, pos asc limit 20, 0;
>>
>> But this query is not using index!
>>
>> The next is result of explain of this query:
>>
>> dsn=# explain select * from pgsql_bbs where topic = 'qna' and deleted < 2
>> dsn-#        order by gid desc, pos asc limit 20, 0;
>> NOTICE:  QUERY PLAN:
>>
>> Limit  (cost=15.71..15.71 rows=11 width=245)
>>   ->  Sort  (cost=15.71..15.71 rows=11 width=245)
>>         ->  Index Scan using pgsql_topic_deleted on pgsql_bbs  (cost=0.00..15.51 rows=11 widt
>h=245)
>
>It appears to be using the topic_deleted index according to this
>explain output.
>How many rows actually have topic='qna' and deleted<2?
-- 
====================================================
mailto:advance@advance.sarang.net
http://database.sarang.net
Dept of Neurosurgery, Dong-eui Medical Center
====================================================