"Pavel Stehule" <pavel(dot)stehule(at)gmail(dot)com> writes:
> select a, b from t group by grouping sets(a, b);
> is same as:
> select a, NULL from t group by a
> union all
> select NULL, b from t group by b;
Really? That seems utterly bizarre, not to say pointless.
You sure you read the spec correctly?
regards, tom lane