Module mz_transform::source ·
Remove Threshold operators when we are certain no records have negative multiplicity.
If we have Threshold(A - Subset(A)) and we believe that A has no negative multiplicities, then we can replace this with A - Subset(A).
The Subset(X) notation means that the collection is a multiset subset of X: multiplicities of each record in Subset(X) are at most that of X.
Remove Threshold operators that have no effect.
Returns true iff
rhsis always a subset of