maleadt commented on issue #506:
URL: https://github.com/apache/arrow-julia/issues/506#issuecomment-2127382038
Thanks for the quick comments!
> The workaround is to ask DataFrames to copy the columns:
>
> ```julia
> DataFrame(Arrow.Table("/tmp/test.arrow")); copycols=true)
> ```
Hmm, I don't see any effect of that here:
```julia
julia> typeof(df.foo)
Vector{Vector{Int64}} (alias for Array{Array{Int64, 1}, 1})
julia> Arrow.write("/tmp/test.arrow", df);
julia> df2 = DataFrame(Arrow.Table("/tmp/test.arrow"); copycols=true);
julia> typeof(df2.foo)
Vector{SubArray{Int64, 1, Primitive{Int64, Vector{Int64}},
Tuple{UnitRange{Int64}}, true}} (alias for Array{SubArray{Int64, 1,
Arrow.Primitive{Int64, Array{Int64, 1}}, Tuple{UnitRange{Int64}}, true}, 1})
```
The snippet you posted is a little ambiguous, but additionally calling
`copy` or `DataFrame` with `copycols=true` (which seems like the default for
`copy` anyway) doesn't help either:
```julia
julia> df2 = DataFrame(DataFrame(Arrow.Table("/tmp/test.arrow"));
copycols=true);
julia> typeof(df2.foo)
Vector{SubArray{Int64, 1, Primitive{Int64, Vector{Int64}},
Tuple{UnitRange{Int64}}, true}} (alias for Array{SubArray{Int64, 1,
Arrow.Primitive{Int64, Array{Int64, 1}}, Tuple{UnitRange{Int64}}, true}, 1})
julia> df2 = copy(DataFrame(Arrow.Table("/tmp/test.arrow")); copycols=true);
julia> typeof(df2.foo)
Vector{SubArray{Int64, 1, Primitive{Int64, Vector{Int64}},
Tuple{UnitRange{Int64}}, true}} (alias for Array{SubArray{Int64, 1,
Arrow.Primitive{Int64, Array{Int64, 1}}, Tuple{UnitRange{Int64}}, true}, 1})
```
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