tustvold commented on issue #4664:
URL: https://github.com/apache/arrow-rs/issues/4664#issuecomment-1676091528
Having spent a significant amount of time working on this I'm inclined to
not move forward with this.
* Decimal256 supports up to 76 decimal digits, which is more than most
commercial systems, and makes me think supporting precision loss arithmetic,
i.e. arithmetic with even greater precision than this, is of limited practical
utility:
* MySQL - 65
* MariaDB - 65
* SQL Server - 38
* DuckDB - 38
* Oracle - 38
* Redshift - 38
* Postgres - 131072!! (postgres decimals appear to be rather special)
* Silently truncating precision is potentially surprising and is
inconsistent with the rest of the arithmetic kernels
* Users can easily increase/decrease the precision of a calculation by
casting the inputs
* Performant precision-loss arithmetic is extremely complex
* Ensuring good test coverage is very hard given the size of the numbers
involved
* I personally find it hard to justify spending significant amounts of time
on decimals when they don't show up in my workloads
TLDR the current decimal support, whilst perhaps not perfect, covers most
bases and I struggle to justify spending more time working on it
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