Re: Group by more efficient than distinct? - Mailing list pgsql-performance

From Francisco Reyes
Subject Re: Group by more efficient than distinct?
Date
Msg-id cone.1208704536.428347.85914.1000@zoraida.natserv.net
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In response to Group by more efficient than distinct?  (Francisco Reyes <lists@stringsutils.com>)
Responses Re: Group by more efficient than distinct?
List pgsql-performance
PFC writes:

>- If you process up to some percentage of your RAM worth of data, hashing
> is going to be a lot faster

Thanks for the excellent breakdown and explanation. I will try and get sizes
of the tables in question and how much memory the machines have.

>     - If you need DISTINCT ON, well, you're stuck with the Sort
>     - So, for the time being, you can replace DISTINCT with GROUP BY...

Have seen a few of those already on some code (new job..) so for those it is
a matter of having a good disk subsystem?

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