[jira] [Created] (FLINK-22586) Improve precision derivation for decimal arithmetics

[Shang Yuanchun (Jira)]

Shuo Cheng created FLINK-22586:
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             Summary: Improve precision derivation for decimal arithmetics
                 Key: FLINK-22586
                 URL: https://issues.apache.org/jira/browse/FLINK-22586
             Project: Flink
          Issue Type: Improvement
          Components: Table SQL / Runtime
    Affects Versions: 1.13.0
            Reporter: Shuo Cheng
             Fix For: 1.14.0


Currently the precision and scale derivation is not properly for decimal data arithmetics, e.g,

considering the following example:
{code:java}
select cast('10.1' as decimal(38, 19)) * cast('10.2' as decimal(38, 19)) from T{code}
the result is `null`, which may confuses use a lot, because the result is far from overflow actually. 

The root cause is the precision derivation for the above multiplication is:

(38, 19) * (38, 19) -> (38, 38)

So there is no space for integral digits, which leads to null results.



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