Github user LosD commented on the issue:
https://github.com/apache/metamodel/pull/128
Of course the other direction is possible. Just cast to a double first.
Changing automatically is a destructive operation, which there will be no way
to avoid.
ANSI SQL says "don't lose precision", which is only possible if you aren't
using long (Since double only has a 52-bit mantissa). Then you could make long
a special case. And decimal is a special case as well. Making 32-bit and lower
ints the only data types that does not return its own datatype. And then we're
really in inconsistent-land.
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