Github user kaspersorensen commented on the issue:
https://github.com/apache/metamodel/pull/171
Darn it ... Seems we have something rotten in our handling of scalar
functions. Have been trying to sort out that issue all night now, and still not
fixed it. In short, we evaluate scalar functions in two different ways, (1) via
`ScalarFunctionDataSet` and (2) via `FilteredItem`. I've been trying to
consolidate it to _only_ be via (1), but there are still failing tests and
stuff. Putting this PR on hold...
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