Give SingletonVector{<:NamedTuple} the Tables.jl interface

This improves performance with TypedTables.
JuliaFolds · Nov 5, 2019 · 0eb3142 · 0eb3142
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commit 0eb3142
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diff --git a/src/NoBang/NoBang.jl b/src/NoBang/NoBang.jl
@@ -6,6 +6,7 @@ using Base.Iterators: Pairs
 using Base: ImmutableDict
 using Requires
 using ConstructionBase: constructorof, setproperties
+using Tables: Tables
 
 using ..BangBang: push!!, ismutable
 

diff --git a/src/NoBang/singletoncontainers.jl b/src/NoBang/singletoncontainers.jl
@@ -12,6 +12,15 @@ function Base.getindex(v::SingletonVector, i::Integer)
     return v.value
 end
 
+# Define table interface as a `SingletonVector{<:NamedTuple}`:
+Tables.istable(::Type{<:SingletonVector{<:NamedTuple{names}}}) where {names} = @isdefined(names)
+Tables.rowaccess(::Type{<:SingletonVector{names}}) where {names} = @isdefined(names)
+Tables.columnaccess(::Type{<:SingletonVector{names}}) where {names} = @isdefined(names)
+
+Tables.rows(x::SingletonVector{<:NamedTuple}) = [x.value]
+Tables.columns(x::SingletonVector{<:NamedTuple{names}}) where names =
+    NamedTuple{names}(map(x -> [x], Tuple(x.value)))
+
 
 struct SingletonDict{K, V} <: AbstractDict{K, V}
     key::K

diff --git a/test/test_typedtables.jl b/test/test_typedtables.jl
@@ -27,4 +27,8 @@ end
     @test_broken tints == Table(a = [1, 3], b = [2, 4])
 end
 
+@testset "type inference" begin
+    @test (@inferred singletonof(Table, (a=1,))) == Table((a=[1]))
+end
+
 end  # module