decimal division gives wrong answer

[kmitchener]

Describe the bug
A clear and concise description of what the bug is.

❯ select 10.1::decimal(5,1)/a from (values (1),(null)) as t(a);
+---------------------------+
| Float64(10.1) / t.a       |
+---------------------------+
| 10.0999999999999997902848 |
|                           |
+---------------------------+
2 rows in set. Query took 0.005 seconds.

Note also that the return type is correctly Decimal, it's just giving wrong results because it's using float internally to do the division.

❯ select arrow_typeof(10.1::decimal(5,1)/a) from (values (1),(null)) as t(a);
+----------------------------------+
| arrowtypeof(Float64(10.1) / t.a) |
+----------------------------------+
| Decimal128(26, 22)               |
| Decimal128(26, 22)               |
+----------------------------------+
2 rows in set. Query took 0.010 seconds.

To Reproduce
Steps to reproduce the behavior:

Expected behavior
A clear and concise description of what you expected to happen.

This should return 10.1 and null.

Additional context
Add any other context about the problem here.

[eejbyfeldt]

On main the example currently produces

DataFusion CLI v42.1.0
> select 10.1::decimal(5,1)/a from (values (1),(null)) as t(a);
+---------------------+
| Float64(10.1) / t.a |
+---------------------+
| 10.10000            |
|                     |
+---------------------+
2 row(s) fetched. 
Elapsed 0.017 seconds.

@alamb I think this issue can be closed as resolved.

[alamb]

Thanks @eejbyfeldt -- I agree.