Hi,
The AggregateUnionTransposeRule attempts to push the Aggregate below the
Union.
Before:
Aggregate[group=$0, agg=SUM($1]
Union[all]
Input1
Input2
After:
Aggregate[group=$0, agg=SUM($1]
Union[all]
Aggregate[group=$0, agg=SUM($1]
Input1
Aggregate[group=$0, agg=SUM($1]
Input2
When pushing the Aggregate, it checks whether the input is definitively
unique on the grouping key. If yes, the Aggregate is not installed on top
of the input, assuming that the result would be the same as without the
Aggregate. This generates a type mismatch exception when aggregation is
pushed only to some of the inputs:
Aggregate[group=$0, agg=SUM($1]
Union[all]
Aggregate[group=$0, agg=SUM($1]
Input1
Input2
It seems that the uniqueness check should not be in that rule at all, and
the aggregate should be pushed unconditionally. Motivation: we already have
AggregateRemoveRule that removes unnecessary aggregates. No need to
duplicate the same non-trivial logic twice.
Does the proposal make sense to you?
Regards,
Vladimir.
