Fix issue with Parallel reapply

Author: juliohm

src/transforms.jl

@@ -201,7 +201,7 @@ function reapply(transform::Colwise, table, cache)
   end
 
   # parallel map with multiple threads
-  vals = foldxt(vcat, Map(colfunc), 1:length(names))
+  vals = tcollect(colfunc(i) for i in 1:length(names))
 
   # new table with transformed columns
   newtable = (; vals...) |> Tables.materializer(table)

src/transforms/parallel.jl

@@ -78,9 +78,9 @@ function reapply(p::Parallel, table, cache)
   caches = cache[2]
 
   # reapply transforms in parallel
-  f((t,c)) = reapply(t, table, c) |> first
+  f(t, c)  = reapply(t, table, c) |> first
   itr      = zip(p.transforms, caches)
-  tables   = foldxt(vcat, Map(f), itr)
+  tables   = tcollect(f(t, c) for (t, c) in itr)
 
   # table with concatenated columns
   newtable = tablehcat(tables)

test/transforms.jl

@@ -406,5 +406,13 @@
     @test isapprox(std(n.x), 1.0, atol=1e-8)
     @test isapprox(mean(r.x), mean(t.x), atol=1e-8)
     @test isapprox(std(r.x), std(t.x), atol=1e-8)
+
+    # reapply with Parallel transform
+    t = Table(x=rand(1000))
+    T = ZScore() ⊔ Quantile()
+    n1, c1 = apply(T, t)
+    n2, c2 = reapply(T, t, c1)
+    @test n1 == n2
+    @test c1 == c2
   end
 end