Customer reported error and Support was able to reproduce on a single server system running 1.4.2. It as customer reported, it did successfully work on 1.2.5.
This issue is within the new 1.4.2 Columnstore/Server instance that does not occur on 1.2.5 Columnstore.
The group by order seems to be handled differently now. Both 1.4.2 and 1.2.5 instances tables are the same, but when the same query is run, it errors on 1.4.2 only.
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