Remove reversibility from transforms: 'Map', 'Replace', 'Sample' and …

…'Sort' (#258)

src/transforms/map.jl

@@ -57,7 +57,7 @@ function Map(pairs::MapPair...)
   Map(selectors, funs, targets)
 end
 
-isrevertible(::Type{Map}) = true
+isrevertible(::Type{Map}) = false
 
 _makename(snames, fun) = Symbol(join([snames; nameof(fun)], "_"))
 
@@ -73,10 +73,6 @@ function applyfeat(transform::Map, feat, prep)
   names = collect(onames)
   columns = Any[Tables.getcolumn(cols, nm) for nm in onames]
 
-  # replaced names and columns
-  rnames = empty(names)
-  rcolumns = empty(columns)
-
   # mapped columns
   mapped = map(selectors, funs, targets) do selector, fun, target
     snames = selector(names)
@@ -88,9 +84,7 @@ function applyfeat(transform::Map, feat, prep)
 
   for (name, column) in mapped
     if name ∈ onames
-      push!(rnames, name)
       i = findfirst(==(name), onames)
-      push!(rcolumns, columns[i])
       columns[i] = column
     else
       push!(names, name)
@@ -100,22 +94,5 @@ function applyfeat(transform::Map, feat, prep)
 
   𝒯 = (; zip(names, columns)...)
   newfeat = 𝒯 |> Tables.materializer(feat)
-  newfeat, (onames, rnames, rcolumns)
-end
-
-function revertfeat(::Map, newfeat, fcache)
-  cols = Tables.columns(newfeat)
-
-  onames, rnames, rcolumns = fcache
-  ocolumns = map(onames) do name
-    if name ∈ rnames
-      i = findfirst(==(name), rnames)
-      rcolumns[i]
-    else
-      Tables.getcolumn(cols, name)
-    end
-  end
-
-  𝒯 = (; zip(onames, ocolumns)...)
-  𝒯 |> Tables.materializer(newfeat)
+  newfeat, nothing
 end

src/transforms/replace.jl

@@ -58,7 +58,7 @@ function Replace(pairs::Pair...)
   Replace(selectors, preds, news)
 end
 
-isrevertible(::Type{<:Replace}) = true
+isrevertible(::Type{<:Replace}) = false
 
 function applyfeat(transform::Replace, feat, prep)
   cols = Tables.columns(feat)
@@ -81,43 +81,23 @@ function applyfeat(transform::Replace, feat, prep)
     name => reps
   end
 
-  tuples = map(colreps) do (name, reps)
+  columns = map(colreps) do (name, reps)
     x = Tables.getcolumn(cols, name)
     if isnothing(reps)
-      x, nothing
+      x
     else
-      # reversal dict
-      rev = Dict{Int,eltype(x)}()
-      y = map(enumerate(x)) do (i, v)
+      map(x) do v
         for (pred, new) in reps
           if pred(v)
-            rev[i] = v
             return new
           end
         end
         v
       end
-      y, rev
     end
   end
 
-  columns = first.(tuples)
-  fcache = last.(tuples)
-
   𝒯 = (; zip(names, columns)...)
   newfeat = 𝒯 |> Tables.materializer(feat)
-  newfeat, fcache
-end
-
-function revertfeat(::Replace, newfeat, fcache)
-  cols = Tables.columns(newfeat)
-  names = Tables.columnnames(cols)
-
-  columns = map(names, fcache) do name, rev
-    y = Tables.getcolumn(cols, name)
-    isnothing(rev) ? y : [get(rev, i, y[i]) for i in 1:length(y)]
-  end
-
-  𝒯 = (; zip(names, columns)...)
-  𝒯 |> Tables.materializer(newfeat)
+  newfeat, nothing
 end

src/transforms/sample.jl

@@ -40,7 +40,7 @@ Sample(size::Int, weights::AbstractWeights; replace=false, ordered=false, rng=Ra
 
 Sample(size::Int, weights; kwargs...) = Sample(size, Weights(collect(weights)); kwargs...)
 
-isrevertible(::Type{<:Sample}) = true
+isrevertible(::Type{<:Sample}) = false
 
 function preprocess(transform::Sample, feat)
   # retrieve valid indices
@@ -59,46 +59,16 @@ function preprocess(transform::Sample, feat)
     sample(rng, inds, weights, size; replace, ordered)
   end
 
-  # rejected indices
-  rinds = setdiff(inds, sinds)
-
-  sinds, rinds
+  sinds
 end
 
 function applyfeat(::Sample, feat, prep)
   # preprocessed indices
-  sinds, rinds = prep
+  sinds = prep
 
-  # selected/rejected rows
+  # selected rows
   srows = Tables.subset(feat, sinds, viewhint=true)
-  rrows = Tables.subset(feat, rinds, viewhint=true)
 
   newfeat = srows |> Tables.materializer(feat)
-  newfeat, (sinds, rinds, rrows)
-end
-
-function revertfeat(::Sample, newfeat, fcache)
-  cols = Tables.columns(newfeat)
-  names = Tables.columnnames(cols)
-
-  sinds, rinds, rrows = fcache
-
-  # columns with selected rows in original order
-  uinds = indexin(sort(unique(sinds)), sinds)
-  columns = map(names) do name
-    y = Tables.getcolumn(cols, name)
-    [y[i] for i in uinds]
-  end
-
-  # insert rejected rows into columns
-  rrcols = Tables.columns(rrows)
-  for (name, x) in zip(names, columns)
-    r = Tables.getcolumn(rrcols, name)
-    for (i, v) in zip(rinds, r)
-      insert!(x, i, v)
-    end
-  end
-
-  𝒯 = (; zip(names, columns)...)
-  𝒯 |> Tables.materializer(newfeat)
+  newfeat, nothing
 end

src/transforms/sort.jl

@@ -34,7 +34,7 @@ Sort(cols::C...; kwargs...) where {C<:Column} = Sort(selector(cols), values(kwar
 
 Sort(; kwargs...) = throw(ArgumentError("cannot create Sort transform without arguments"))
 
-isrevertible(::Type{<:Sort}) = true
+isrevertible(::Type{<:Sort}) = false
 
 function preprocess(transform::Sort, feat)
   cols = Tables.columns(feat)
@@ -59,18 +59,5 @@ function applyfeat(::Sort, feat, prep)
 
   newfeat = srows |> Tables.materializer(feat)
 
-  newfeat, sinds
-end
-
-function revertfeat(::Sort, newfeat, fcache)
-  # collect all rows
-  rows = Tables.rowtable(newfeat)
-
-  # reverting indices
-  sinds = fcache
-  rinds = sortperm(sinds)
-
-  rrows = view(rows, rinds)
-
-  rrows |> Tables.materializer(newfeat)
+  newfeat, nothing
 end

test/transforms/map.jl

@@ -1,4 +1,6 @@
 @testset "Map" begin
+  @test !isrevertible(Map(:a => sin))
+
   a = [4, 7, 8, 5, 8, 1]
   b = [1, 9, 1, 7, 9, 4]
   c = [2, 8, 6, 3, 2, 2]
@@ -9,65 +11,47 @@
   n, c = apply(T, t)
   @test Tables.schema(n).names == (:a, :b, :c, :d, :a_sin)
   @test n.a_sin == sin.(t.a)
-  tₒ = revert(T, n, c)
-  @test t == tₒ
 
   T = Map(:b => cos)
   n, c = apply(T, t)
   @test Tables.schema(n).names == (:a, :b, :c, :d, :b_cos)
   @test n.b_cos == cos.(t.b)
-  tₒ = revert(T, n, c)
-  @test t == tₒ
 
   T = Map("c" => tan)
   n, c = apply(T, t)
   @test Tables.schema(n).names == (:a, :b, :c, :d, :c_tan)
   @test n.c_tan == tan.(t.c)
-  tₒ = revert(T, n, c)
-  @test t == tₒ
 
   T = Map(:a => sin => :a)
   n, c = apply(T, t)
   @test Tables.schema(n).names == (:a, :b, :c, :d)
   @test n.a == sin.(t.a)
-  tₒ = revert(T, n, c)
-  @test t == tₒ
 
   T = Map(:a => sin => "a")
   n, c = apply(T, t)
   @test Tables.schema(n).names == (:a, :b, :c, :d)
   @test n.a == sin.(t.a)
-  tₒ = revert(T, n, c)
-  @test t == tₒ
 
   T = Map([2, 3] => ((b, c) -> 2b + c) => :op1)
   n, c = apply(T, t)
   @test Tables.schema(n).names == (:a, :b, :c, :d, :op1)
   @test n.op1 == @. 2 * t.b + t.c
-  tₒ = revert(T, n, c)
-  @test t == tₒ
 
   T = Map([:a, :c] => ((a, c) -> 2a * 3c) => :op1)
   n, c = apply(T, t)
   @test Tables.schema(n).names == (:a, :b, :c, :d, :op1)
   @test n.op1 == @. 2 * t.a * 3 * t.c
-  tₒ = revert(T, n, c)
-  @test t == tₒ
 
   T = Map(["c", "a"] => ((c, a) -> 3c / a) => :op1, "c" => tan)
   n, c = apply(T, t)
   @test Tables.schema(n).names == (:a, :b, :c, :d, :op1, :c_tan)
   @test n.op1 == @. 3 * t.c / t.a
   @test n.c_tan == tan.(t.c)
-  tₒ = revert(T, n, c)
-  @test t == tₒ
 
   T = Map(r"[abc]" => ((a, b, c) -> a^2 - 2b + c) => "op1")
   n, c = apply(T, t)
   @test Tables.schema(n).names == (:a, :b, :c, :d, :op1)
   @test n.op1 == @. t.a^2 - 2 * t.b + t.c
-  tₒ = revert(T, n, c)
-  @test t == tₒ
 
   # throws
   @test_throws ArgumentError Map()