fix(csharp/src/Drivers/Apache): set the precision and scale correctly on Decimal128Type

[birschick-bq]

Addresses a TODO item to accurately retrieve the precision and scale for DECIMAL (Decimal128Type) when retrieving table schema (GetTableSchema).

• Parses the type name to find the precision and scale, using the default of 10 and 0, respectively.

[CurtHagenlocher]

Thanks for the change! I don't understand how decimal types are even usable if we don't know the scale of the result. Are there known circumstances where that's true?

How were 10 and 0 chosen as the defaults for precision and scale?

[CurtHagenlocher]

These should probably be TryParse; the capture might succeed but capture so many digits that the Parse will throw an exception. Alternatively, the regex could probably specify a range of lengths -- but TryParse seems like a safer and more readable approach to me.

[CurtHagenlocher]

What will happen for statement results? And does that code path go through here?

[birschick-bq]

Statement results has its own metadata. The statement's result set metadata DOES contain precision and scale. So runtime was already working. This is only for the AdbcConnection.GetTableMetadata path.

I think this comment might be misleading. What is meant to convey is that this technique can't be used for handling complex types like ARRAY, MAP, and STRUCT with statement results.

Might just remove the comment.

[birschick-bq]

Thanks for the change! I don't understand how decimal types are even usable if we don't know the scale of the result. Are there known circumstances where that's true?

How were 10 and 0 chosen as the defaults for precision and scale?

These changes affect AdbcConnection.GetTableSchema and not any of the ExecuteQuery/ExecuteUpdate. They (statement results) have a separate metadata that DOES include the precision and scale. (Unfortunately, statement result metadata does not include metadata for complex types.)

The default are chose from https://docs.databricks.com/en/sql/language-manual/data-types/decimal-type.html#syntax

            // { DECIMAL | DEC | NUMERIC } [ (  p [ , s ] ) ]
            // p: Optional maximum precision (total number of digits) of the number between 1 and 38. The default is 10.
            // s: Optional scale of the number between 0 and p. The number of digits to the right of the decimal point. The default is 0.