>
> Controls if the query planner will produce a plan which will provide
> <literal>GROUP BY</literal> keys presorted in the order of keys of a child
> node of the plan, such as an index scan. When disabled, the query planner
> will produce a plan with <literal>GROUP BY</literal> keys only reordered to
> match
> the <literal>ORDER BY</literal> clause, if any. When enabled, the planner
> will try to produce a more efficient plan. The default value is on.
>
A correction of myself: presorted -> sorted, reordered ->sorted
Regards,
Pavel