add optimized append (#111)

* add optimized append

* only do optimization on julia 1.3

* add tests

Author: Pietro Vertechi

src/collect.jl

@@ -64,7 +64,7 @@ _collect_structarray!(dest, itr, st, ::Nothing) =
 
 function collect_to_structarray!(dest::AbstractArray, itr, offs, st)
     # collect to dest array, checking the type of each result. if a result does not
-    # match, widen the result type and re-dispatch.
+    # match, widen_from_instance the result type and re-dispatch.
     i = offs
     while true
         elem = iterate(itr, st)
@@ -74,7 +74,7 @@ function collect_to_structarray!(dest::AbstractArray, itr, offs, st)
             @inbounds dest[i] = el
             i += 1
         else
-            new = widen(dest, i, el)
+            new = widen_from_instance(dest, i, el)
             @inbounds new[i] = el
             return collect_to_structarray!(new, itr, i+1, st)
         end
@@ -84,7 +84,7 @@ end
 
 function grow_to_structarray!(dest::AbstractArray, itr, elem = iterate(itr))
     # collect to dest array, checking the type of each result. if a result does not
-    # match, widen the result type and re-dispatch.
+    # match, widen_from_instance the result type and re-dispatch.
     i = length(dest)+1
     while elem !== nothing
         el, st = elem
@@ -93,7 +93,7 @@ function grow_to_structarray!(dest::AbstractArray, itr, elem = iterate(itr))
             elem = iterate(itr, st)
             i += 1
         else
-            new = widen(dest, i, el)
+            new = widen_from_instance(dest, i, el)
             push!(new, el)
             return grow_to_structarray!(new, itr, iterate(itr, st))
         end
@@ -102,7 +102,12 @@ function grow_to_structarray!(dest::AbstractArray, itr, elem = iterate(itr))
 end
 
 # Widen `dest` to contain `el` and copy until index `i-1`
-widen(dest::AbstractArray{S}, i, el::T) where {S, T} = _widenstructarray(dest, i, _promote_typejoin(S, T))
+widen_from_instance(dest::AbstractArray, i, el::T) where {T} = widen_from_type(dest, i, T)
+# Widen `dest` to contain elements of type `T` and copy until index `i-1`
+function widen_from_type(dest::AbstractArray{S}, i, ::Type{T}) where {S, T}
+    U = _promote_typejoin(S, T)
+    return _widenstructarray(dest, i, U)
+end
 
 function _widenstructarray(dest::StructArray, i, ::Type{T}) where {T}
     sch = hasfields(T) ? staticschema(T) : nothing
@@ -145,11 +150,20 @@ function _append!!(dest::AbstractVector, itr, ::Union{Base.HasShape, Base.HasLen
     fr === nothing && return dest
     el, st = fr
     i = lastindex(dest) + 1
-    new = iscompatible(el, dest) ? dest : widen(dest, i, el)
+    new = iscompatible(el, dest) ? dest : widen_from_instance(dest, i, el)
     resize!(new, length(dest) + n)
     @inbounds new[i] = el
     return collect_to_structarray!(new, itr, i + 1, st)
 end
 
 _append!!(dest::AbstractVector, itr, ::Base.SizeUnknown) =
     grow_to_structarray!(dest, itr)
+
+# Optimized version when element collection is an `AbstractVector`
+# This only works for julia 1.3 or greater, which has `append!` for `AbstractVector`
+@static if VERSION ≥ v"1.3.0"
+    function append!!(dest::V, v::AbstractVector{T}) where {V<:AbstractVector, T}
+        new = iscompatible(T, V) ? dest : widen_from_type(dest, length(dest) + 1, T)
+        return append!(new, v)
+    end
+end

src/structarray.jl

@@ -169,12 +169,12 @@ Base.@propagate_inbounds function Base.setindex!(s::StructArray{<:Any, <:Any, <:
     s
 end
 
-function Base.push!(s::StructArray, vals)
+function Base.push!(s::StructVector, vals)
     foreachfield(push!, s, vals)
     return s
 end
 
-function Base.append!(s::StructArray, vals)
+function Base.append!(s::StructVector, vals::StructVector)
     foreachfield(append!, s, vals)
     return s
 end

test/runtests.jl

@@ -681,6 +681,7 @@ end
     itr = [(a = 1, b = 2), (a = 1, b = 2), (a = 1, b = 12)]
     itr_examples = [
         ("HasLength", () -> itr),
+        ("StructArray", () -> StructArray(itr)),
         ("SizeUnknown", () -> (x for x in itr if isodd(x.a))),
         # Broken due to https://github.com/JuliaArrays/StructArrays.jl/issues/100:
         # ("empty", (x for x in itr if false)),