Re: Bad plan for join to aggregate of join. - Mailing list pgsql-performance

Tom Lane wrote:
> Mischa Sandberg <mischa@ca.sophos.com> writes:
>> can PG see that a join on an grouped-by field
>> can be pushed down into the query as an indexable filter?
>
> No.  The GROUP BY serves as a partial optimization fence.  If you're
> concerned about the speed of this query, I recommend making a different
> view in which 'message' is joined inside the GROUP BY.

Thanks.