add nicer reduce for grouped dtable

src/table/gdtable.jl

@@ -6,6 +6,8 @@ mutable struct GDTable
     index::Dict
 end
 
+grouped_cols(gd::GDTable) = gd.cols === nothing ? [:keys] : gd.cols
+
 keys(gd::GDTable) = keys(gd.index)
 
 fetch(gd::GDTable) = fetch(gd.dtable)

src/table/operations.jl

@@ -98,16 +98,22 @@ function reduce(f, d::DTable; cols=nothing::Union{Nothing, Vector{Symbol}}, init
     construct_single_column = (_col, _chunk_results...) -> getindex.(_chunk_results, _col)
     result_columns = [Dagger.@spawn construct_single_column(c, chunk_reduce_results...) for c in columns]
 
-    reduce_result_column = (_f, _c, _init) -> reduce(_f, _c; init=_init)
-    reduce_chunks = [Dagger.@spawn reduce_result_column(f, c, deepcopy(init)) for c in result_columns]
+    reduce_result_column = (_f, _c) -> reduce(_f, _c) # removed init from here as it's not needed (couldn't do (x,y)->x+1 for example)
+    reduce_chunks = [Dagger.@spawn reduce_result_column(f, c) for c in result_columns]
 
     construct_result = (_cols, _vals...) -> (; zip(_cols, _vals)...)
     Dagger.@spawn construct_result(columns, reduce_chunks...)
 end
 
 
 function reduce(f, gd::GDTable; cols=nothing::Union{Nothing, Vector{Symbol}}, init=Base._InitialValue())
-    Dict([d[1] => reduce(f, d[2]; cols=cols, init=init) for d in gd])
+    construct_result = (_keys, _results...) -> begin
+        result_cols = keys(first(_results))
+        k = [col => getindex.(_keys, i) for (i, col) in enumerate(grouped_cols(gd))]
+        r = [Symbol("result_" * string(r)) => collect(getindex.(_results, r)) for r in result_cols]
+        (;k...,r...)
+    end
+    Dagger.@spawn construct_result(keys(gd), [reduce(f, d[2]; cols=cols, init=deepcopy(init)) for d in gd]...)
 end
 
 """