Re: Additional select fields in a GROUP BY - Mailing list pgsql-performance

Vitaly Belman <vitalyb@gmail.com> writes:
> Notice that the GROUP BY items added the following to the plan:

>               ->  Sort  (cost=10454.67..10600.83 rows=58466 width=47)
>                     Sort Key: s.series_id, s.series_name, s.series_picture

Oh, I see: in the first case you need no sort at all because the output
of the indexscan is already known to be sorted by s.series_id.  I was
thinking of a sort with more or fewer sort columns, but that's not the
issue here.

            regards, tom lane