Github user kaspersorensen commented on the issue:
https://github.com/apache/metamodel/pull/171
There! I believe it's all fixed now. Took me some real digging around and
eventually found that due to a bad `SelectItem.equals(Object)` method, the two
scalar function SelectItems was reduced to one. Ended up adding a whole slew of
unit tests to finally identify that this (and probably a few other tweaks) was
the root cause.
If you'd like, I can change the PR to be more minimalistic. But I kind of
like every little tweak that was done TBH, so this here is my suggested patch.
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