bug fix

Author: sl-solution

src/other/utils.jl

@@ -18,7 +18,9 @@ end
 Missings.allowmissing(a::PooledArray) = convert(PooledArray{Union{Missing, eltype(a)}}, a)
 
 function allocatecol(x::AbstractVector, len; addmissing = true)
-    @assert len > 0 "cannot allocate a column with length zero"
+    if addmissing
+        @assert len > 0 "cannot allocate a column with length zero"
+    end
     if DataAPI.refpool(x) !== nothing
         if x isa PooledArray
             _res = PooledArray(PooledArrays.RefArray(x.refs[1:1]), DataAPI.invrefpool(x), DataAPI.refpool(x), PooledArrays.refcount(x))

test/join.jl

@@ -401,6 +401,9 @@ end
 
     @test o(on) == Dataset(id = [1, 3, 5, 0, 2, 4], fid = [1, 3, 5, 0, 2, 4])
     @test typeof.(eachcol(o(on))) == [Vector{Union{Missing, Int}}, Vector{Union{Missing, Float64}}]
+    dsl = Dataset(x=[1,2], y=[3,4])
+    re = innerjoin(dsl, dsl, on = [:x=>:y], makeunique = true)
+    @test Dataset([[],[],[]], names(re)) == re
 end
 #
 # @testset "all joins with CategoricalArrays" begin