Support for Decimal256

[Sunyue]

Currently we see Decimal128 is supported through types.Decimal, any chance that higher precision decimal like decimal256 can be supported? Thanks!

[EpsilonPrime]

I can see two ways of implementing a wider decimal type. The simplest would be to introduce a new type (either external or part of the spec). That would also require updating or duplicating all of the functions that take Decimal. The other would be to treat it logically and require the use of type variations to tell the two apart.

There are other potential Decimal implementations out there. For instance Snowflake uses a Decimal128 where you can get just a bit beyond 38 places of precision using the extra bot space. It'd be useful to consider this when trying to make an implementation decision.