+1 adding 32 and 64 bit decimals.
+0 to release it without integration tests - both IPC and the C data
interface use a variable bit width to declare the appropriate size for
decimal types. Relaxing from {128,256} to {32,64,128,256} seems a low risk
from an integration perspective, as implementations already need to read
the bitwidth to select the appropriate physical representation (if they
support it).
Best,
Jorge
On Mon, Mar 7, 2022, 11:41 Antoine Pitrou <anto...@python.org> wrote:
>
> Le 03/03/2022 à 18:05, Micah Kornfield a écrit :
> > I think this makes sense to add these. Typically when adding new types,
> > we've waited on the official vote until there are two reference
> > implementations demonstrating compatibility.
>
> You are right, I had forgotten about that. Though in this case, it
> might be argued we are just relaxing the constraints on an existing type.
>
> What do others think?
>
> Regards
>
> Antoine.
>
>
> >
> > On Thu, Mar 3, 2022 at 6:55 AM Antoine Pitrou <anto...@python.org>
> wrote:
> >
> >>
> >> Hello,
> >>
> >> Currently, the Arrow format specification restricts the bitwidth of
> >> decimal numbers to either 128 or 256 bits.
> >>
> >> However, there is interest in allowing other bitwidths, at least 32 and
> >> 64 bits for this proposal. A 64-bit (respectively 32-bit) decimal
> >> datatype would allow for precisions of up to 18 digits (respectively 9
> >> digits), which are sufficient for some applications which are mainly
> >> looking for exact computations rather than sheer precision. Obviously,
> >> smaller datatypes are cheaper to store in memory and cheaper to run
> >> computations on.
> >>
> >> For example, the Spark documentation mentions that some decimal types
> >> may fit in a Java int (32 bits) or long (64 bits):
> >>
> >>
> https://spark.apache.org/docs/latest/api/java/org/apache/spark/sql/types/DecimalType.html
> >>
> >> ... and a draft PR had even been filed for initial support in the C++
> >> implementation (https://github.com/apache/arrow/pull/8578).
> >>
> >> I am therefore proposing that we relax the wording in the Arrow format
> >> specification to also allow 32- and 64-bit decimal types.
> >>
> >> This is a preliminary discussion to gather opinions and potential
> >> counter-arguments against this proposal. If no strong counter-argument
> >> emerges, we will probably run a vote in a week or two.
> >>
> >> Best regards
> >>
> >> Antoine.
> >>
> >
>
