[GitHub] [arrow-julia] ericphanson opened a new issue, #323: [ArrowTypes] add `@arrow_record`?

[GitBox <gi...@apache.org>]

ericphanson opened a new issue, #323:
URL: https://github.com/apache/arrow-julia/issues/323

   @kleinschmidt and I came up with
   ```julia
   using Arrow: ArrowTypes
   macro arrow_record(T)
       name = :(Symbol("JuliaLang.", @__MODULE__, ".", string(parentmodule($T), '.', nameof($T))))
       return quote
          ArrowTypes.arrowname(::Type{$T}) = $name
          ArrowTypes.ArrowType(::Type{$T}) = fieldtypes($T)
          ArrowTypes.toarrow(obj::$T) = ntuple(i -> getfield(obj, i), fieldcount($T))
          ArrowTypes.JuliaType(::Val{$name}, ::Any) = $T
          ArrowTypes.fromarrow(::Type{$T}, args...) = $T(args...)
       end
   end
   ```
   as a quick way to declare that a non-parametrized concrete type should be serialized like a "record" (a la [`StructTypes.StructType`](https://juliadata.github.io/StructTypes.jl/stable/#StructTypes.Struct)). (Or maybe it should be called `@arrow_fields` or something?). In other words, we want it to just serialize out as a tuple of its fields with a metadata tag. This could be used as, e.g.
   
   ```julia
   using Arrow
   
   struct Foo
       bar::String
       x::Int
   end
   
   @arrow_record Foo
   
   my_foo =  Foo("hi", 1)
   table = [(; foo_col=my_foo)]
   roundtripped_table = Arrow.Table(Arrow.tobuffer(table))
   using Test
   @test roundtripped_table.foo_col[1] == my_foo # true
   ```


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