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Also we allow two combinators, one that "combining" the second agg2 with the first partial aggregate agg1, while the other "inverting" the second agg2 from the partial aggregate agg1. This is enabling the library to further explore the invertibility in addition to associativity / commutativity of the aggregation function (more details in http://www.vldb.org/pvldb/vol8/p702-tangwongsan.pdf).

Implementation

Note this would likely have an impact on how we do suppression today: today the aggregation and suppression are totally independent operators, but with this optimization we may consider the suppression effects while implementing the aggregation operators to reduce unnecessary reads on the sub-windows.

References:

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