Type stability of Tables.matrix(::NamedTuple)

[MilesCranmer]

I'm descending some type instability issues in my package and realized that Tables.matrix(::NamedTuple) is not type stable. Would this be feasible to implement?

For example:

julia> using Tables

julia> X = (x=randn(32), y=randn(32));

julia> typeof(Tables.matrix(X))
Matrix{Float64} (alias for Array{Float64, 2})

julia> @code_warntype Tables.matrix(X)
MethodInstance for Tables.matrix(::@NamedTuple{x::Vector{Float64}, y::Vector{Float64}})
  from matrix(table; transpose) @ Tables ~/.julia/packages/Tables/AcRIE/src/matrix.jl:84
Arguments
  #self#::Core.Const(Tables.matrix)
  table::@NamedTuple{x::Vector{Float64}, y::Vector{Float64}}
Body::Matrix
1 ─ %1 = Tables.:(var"#matrix#85")(false, #self#, table)::Matrix
└──      return %1

So the type inference is not able to infer that this is a Matrix{Float64}, only that it is a Matrix{Any}, despite the method call being specialized to a NamedTuple with Vector{Float64} for columns.

Version info:

Julia Version 1.10.0-beta1
Commit 6616549950e (2023-07-25 17:43 UTC)
Platform Info:
  OS: macOS (arm64-apple-darwin22.4.0)
  CPU: 8 × Apple M1 Pro
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, apple-m1)
  Threads: 8 on 6 virtual cores
Environment:
  JULIA_FORMATTER_SO = /Users/mcranmer/julia_formatter.so
  JULIA_NUM_THREADS = auto
  JULIA_EDITOR = code

[MilesCranmer]

It looks like the source of this instability is here (via Cthulhu)

 84 function matrix(table::@NamedTuple{x::Vector{Float64}, y::Vector{Float64}}; transpose::Bool::Bool=false)::Matrix
 85     cols::Tables.Columns{@NamedTuple{x::Vector{Float64}, y::Vector{Float64}}} = Columns::Type{Tables.Columns}(table::@NamedTuple{x::Vector{Float64}, y::Vector{Float64}})::Tables.Columns{@NamedTuple{x::Vector{Float64}, y::Vector{Float64}}}
 86     types::Tuple{Vararg{DataType}} = schema(cols::Tables.Columns{@NamedTuple{x::Vector{Float64}, y::Vector{Float64}}})::Tables.Schema{(:x, :y), Tuple{Float64, Float64}}.types::Tuple{Vararg{DataType}}

So the schema(cols).types is being inferred as a Tuple{Vararg{DataType}} rather than a Tuple{Float64,Float64}.

[MilesCranmer]

I think the issue is that this function:

function Base.getproperty(sch::Schema{names, types}, field::Symbol) where {names, types}
    if field === :names
        return names === nothing ? getfield(sch, :storednames) : names
    elseif field === :types
        T = getfield(sch, :storedtypes)
        return types === nothing ? (T !== nothing ? T : nothing) : Tuple(fieldtype(types, i) for i = 1:fieldcount(types))
    else
        throw(ArgumentError("unsupported property for Tables.Schema"))
    end
end

does not have a type stable return value.

[MilesCranmer]

Fixed in #340!