Refactor Filter implementation: avoid Tables.rowtable (#240)

* Refactor 'Filter' implementation: avoid 'Tables.rowtable'

* Update tests

Author: eliascarv

src/transforms/filter.jl

@@ -47,29 +47,38 @@ function preprocess(transform::Filter, feat)
 end
 
 function applyfeat(::Filter, feat, prep)
-  # collect all rows
-  rows = Tables.rowtable(feat)
-
   # preprocessed indices
   sinds, rinds = prep
 
-  # select/reject rows
-  srows = view(rows, sinds)
-  rrows = view(rows, rinds)
+  # selected/rejected rows
+  srows = Tables.subset(feat, sinds, viewhint=true)
+  rrows = Tables.subset(feat, rinds, viewhint=true)
 
   newfeat = srows |> Tables.materializer(feat)
 
   newfeat, (rinds, rrows)
 end
 
 function revertfeat(::Filter, newfeat, fcache)
-  # collect all rows
-  rows = Tables.rowtable(newfeat)
+  cols = Tables.columns(newfeat)
+  names = Tables.columnnames(cols)
 
   rinds, rrows = fcache
-  for (i, row) in zip(rinds, rrows)
-    insert!(rows, i, row)
+
+  # columns with selected rows
+  columns = map(names) do name
+    collect(Tables.getcolumn(cols, name))
+  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
 
-  rows |> Tables.materializer(newfeat)
+  𝒯 = (; zip(names, columns)...)
+  𝒯 |> Tables.materializer(newfeat)
 end

src/transforms/sample.jl

@@ -58,6 +58,8 @@ function preprocess(transform::Sample, feat)
   else
     sample(rng, inds, weights, size; replace, ordered)
   end
+
+  # rejected indices
   rinds = setdiff(inds, sinds)
 
   sinds, rinds
@@ -67,7 +69,7 @@ function applyfeat(::Sample, feat, prep)
   # preprocessed indices
   sinds, rinds = prep
 
-  # selected and removed rows
+  # selected/rejected rows
   srows = Tables.subset(feat, sinds, viewhint=true)
   rrows = Tables.subset(feat, rinds, viewhint=true)
 
@@ -78,6 +80,7 @@ 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
@@ -87,7 +90,7 @@ function revertfeat(::Sample, newfeat, fcache)
     [y[i] for i in uinds]
   end
 
-  # insert removed rows into columns
+  # insert rejected rows into columns
   rrcols = Tables.columns(rrows)
   for (name, x) in zip(names, columns)
     r = Tables.getcolumn(rrcols, name)

test/transforms/filter.jl

@@ -123,4 +123,14 @@
   @test Tables.isrowtable(n)
   rtₒ = revert(T, n, c)
   @test rt == rtₒ
+
+  # performance tests
+  trng = MersenneTwister(2) # test rng
+  x = rand(trng, 100_000)
+  y = rand(trng, 100_000)
+  c = CoDaArray((a=rand(trng, 100_000), b=rand(trng, 100_000), c=rand(trng, 100_000)))
+  t = (; x, y, c)
+
+  T = Filter(row -> row.x > 0.5)
+  @test @elapsed(apply(T, t)) < 0.5
 end

test/transforms/sample.jl

@@ -62,10 +62,11 @@
   @test isapprox(count(==(trows[6]), nrows) / 10_000, 6 / 21, atol=0.01)
 
   # performance tests
-  x = rand(100_000)
-  y = rand(100_000)
-  c = CoDaArray((a=rand(100_000), b=rand(100_000), c=rand(100_000)))
-  t = Table(; x, y, c)
+  trng = MersenneTwister(2) # test rng
+  x = rand(trng, 100_000)
+  y = rand(trng, 100_000)
+  c = CoDaArray((a=rand(trng, 100_000), b=rand(trng, 100_000), c=rand(trng, 100_000)))
+  t = (; x, y, c)
 
   T = Sample(10_000)
   @test @elapsed(apply(T, t)) < 0.5