Re: Returning the total number of rows as a separate column when using limit

"Gregory Stark" <stark@enterprisedb.com> writes:

> "Andreas Joseph Krogh" <andreak@officenet.no> writes:
>
>> That's what I'm doing now. I run the query with "limit+1" as limit and if it 
>> results in more than limit, I know there is more data and I run count(*) to 
>> count them all. But count(*) cannot use indices in PG so it's limited in 
>> speed anyway AFAICS.
>
> Well count(*) can use indexes the same as the query can.
>
>> I really hoped there was an "Oracle over()" equivalent way in PG. I understand 
>> that Oracle's LIMIT-hack with "3 subselects and rownum between 1 AND 20" is 
>> rather expensive compared to PG's implementation of LIMIT. Oralce keeps 
>> snapshot-info in the index, so counting only involves the index AFAIK.
>
> Well that's only going to be true if the index satisfies the whole query which
> is not going to be true for the simplest cases.

er, *except* for the simplest cases.


--  Gregory Stark EnterpriseDB          http://www.enterprisedb.com Ask me about EnterpriseDB's RemoteDBA services!