Re: Re-Reason of Slowness of Query

[Chetan Suttraway <chetan.suttraway@xxxxxxxxxxxxxxxx>]

On Wed, Mar 23, 2011 at 3:49 PM, Adarsh Sharma <adarsh.sharma@xxxxxxxxxx> wrote:

Vitalii Tymchyshyn wrote:

23.03.11 12:10, Adarsh Sharma ÐÐÐÐÑÐÐ(ÐÐ):

I just want to retrieve that id 's from page_content which do not have any entry in clause2 table.

Then
select distinct(p.crawled_page_id) from page_content p
Âwhere NOT EXISTS (select 1 from clause2 c where c.source_id = p.crawled_page_id);
is correct query.

I can't understand how select 1 from clause2 c where c.source_id = p.crawled_page_id works too, i get my output .

What is the significance of 1 here.

Thanks , Adarsh

Best regards, Vitalii Tymchyshyn.

Its the inverted logic for finding crawled_page_id not matching with source_id.
Actually, the idea was to force index scan on clause2 though.


-- 
Regards,
Chetan Suttraway

EnterpriseDB, TheÂEnterprise PostgreSQLÂcompany.