Re: Performance on large, append-only tables - Mailing list pgsql-performance

On Fri, Feb 10, 2012 at 1:45 PM, David Yeu <david.yeu@skype.net> wrote:
> On Feb 10, 2012, at 11:26 AM, Claudio Freire wrote:
>> That, and an index on "(group_id, created_at) where (deleted_at IS
>> NULL)" to catch the sorted by date kind of query, and you'll be done I
>> think.
>
> Yeah, I didn't quite get that right -- we're actually sorting all these queries by "id DESC", not "created_at DESC",
sothat seems to obviate the need for any index on created_at. 

From your OP:

>  * Š WHERE group_id = ? ORDER BY created_at DESC LIMIT 20;