diff --git a/src/Tables.jl b/src/Tables.jl
index ae41f73..373a472 100644
--- a/src/Tables.jl
+++ b/src/Tables.jl
@@ -6,7 +6,7 @@ export rowtable, columntable
 
 function __init__()
     @require DataValues="e7dc6d0d-1eca-5fa6-8ad6-5aecde8b7ea5" include("datavalues.jl")
-    @require QueryOperators="2aef5ad7-51ca-5a8f-8e88-e75cf067b44b" include("enumerable.jl")
+    @require Query="1a8c2f83-1ff3-5112-b086-8aa67b057ba1" include("enumerable.jl")
     @require CategoricalArrays="324d7699-5711-5eae-9e2f-1d82baa6b597" begin
         using .CategoricalArrays
         allocatecolumn(::Type{CategoricalString{R}}, rows) where {R} = CategoricalArray{String, 1, R}(undef, rows)
diff --git a/src/datavalues.jl b/src/datavalues.jl
index c2862c0..76bf6e2 100644
--- a/src/datavalues.jl
+++ b/src/datavalues.jl
@@ -12,7 +12,7 @@ unwrap(x) = x
 unwrap(x::DataValue) = isna(x) ? missing : DataValues.unsafe_get(x)
 
 datavaluetype(::Type{T}) where {T <: DataValue} = T
-datavaluetype(::Type{T}) where {T} = DataValue{T}
+datavaluetype(::Type{T}) where {T} = T
 datavaluetype(::Type{Union{T, Missing}}) where {T} = DataValue{T}
 Base.@pure function datavaluetype(::Tables.Schema{names, types}) where {names, types}
     TT = Tuple{Any[ datavaluetype(fieldtype(types, i)) for i = 1:fieldcount(types) ]...}
@@ -55,3 +55,16 @@ function Base.iterate(rows::DataValueRowIterator{NT, S}, st=()) where {NT <: Nam
     end
 end
 
+# function Base.iterate(rows::DataValueRowIterator{NT}, st=()) where {NT}
+#     state = iterate(rows.x, st...)
+#     state === nothing && return nothing
+#     row, st = state
+#     return DataValueRow{NT, typeof(row)}(row), (st,)
+# end
+
+# struct DataValueRow{NT, T}
+#     row::T
+# end
+
+# @inline Base.getproperty(dvr::DataValueRow{NamedTuple{names, types}}, nm::Symbol) where {names, types} = getproperty(dvr, Tables.columntype(names, types, nm), Tables.columnindex(names, nm), nm)
+# @inline Base.getproperty(dvr::DataValueRow, ::Type{T}, col::Int, nm::Symbol) where {T} = T(getproperty(getfield(dvr, 1), nondatavaluetype(T), col, nm))
diff --git a/src/enumerable.jl b/src/enumerable.jl
index 5edc8c4..a20c11b 100644
--- a/src/enumerable.jl
+++ b/src/enumerable.jl
@@ -1,5 +1,8 @@
-using .QueryOperators: Enumerable
-using .DataValues
+using .Query
+
+@static if isdefined(Query.QueryOperators, :Enumerable)
+
+import .Query.QueryOperators: Enumerable
 
 Tables.istable(::Type{<:Enumerable}) = true
 Tables.rowaccess(::Type{<:Enumerable}) = true
@@ -9,7 +12,11 @@ struct DataValueUnwrapper{S}
     x::S
 end
 
-Tables.schema(dv::DataValueUnwrapper) = Tables.Schema(nondatavaluetype(eltype(dv.x)))
+function Tables.schema(dv::DataValueUnwrapper)
+    eT = eltype(dv.x)
+    !(eT <: NamedTuple) && return nothing
+    return Tables.Schema(nondatavaluetype(eT))
+end
 Base.eltype(rows::DataValueUnwrapper) = DataValueUnwrapRow{eltype(rows.x)}
 Base.IteratorSize(::Type{DataValueUnwrapper{S}}) where {S} = Base.IteratorSize(S)
 Base.length(rows::DataValueUnwrapper) = length(rows.x)
@@ -28,3 +35,5 @@ end
 Base.getproperty(d::DataValueUnwrapRow, ::Type{T}, col::Int, nm::Symbol) where {T} = unwrap(getproperty(getfield(d, 1), T, col, nm))
 Base.getproperty(d::DataValueUnwrapRow, nm::Symbol) = unwrap(getproperty(getfield(d, 1), nm))
 Base.propertynames(d::DataValueUnwrapRow) = propertynames(getfield(d, 1))
+
+end # isdefined
\ No newline at end of file
diff --git a/src/fallbacks.jl b/src/fallbacks.jl
index ecf1aa4..92bab90 100644
--- a/src/fallbacks.jl
+++ b/src/fallbacks.jl
@@ -3,6 +3,8 @@
 ## we'll provide a default implementation of the dual
 
 # generic row iteration of columns
+rowcount(cols) = length(getproperty(cols, propertynames(cols)[1]))
+
 struct ColumnsRow{T}
     columns::T # a `Columns` object
     row::Int
@@ -14,9 +16,10 @@ Base.propertynames(c::ColumnsRow) = propertynames(getfield(c, 1))
 
 struct RowIterator{T}
     columns::T
+    len::Int
 end
 Base.eltype(x::RowIterator{T}) where {T} = ColumnsRow{T}
-Base.length(x::RowIterator) = length(getproperty(x.columns, propertynames(x.columns)[1]))
+Base.length(x::RowIterator) = x.len
 schema(x::RowIterator) = schema(x.columns)
 
 function Base.iterate(rows::RowIterator, st=1)
@@ -26,7 +29,8 @@ end
 
 function rows(x::T) where {T}
     if columnaccess(T)
-        return RowIterator(columns(x))
+        cols = columns(x)
+        return RowIterator(cols, rowcount(cols))
     else
         throw(ArgumentError("no default `Tables.rows` implementation for type: $T"))
     end
@@ -90,7 +94,7 @@ end
 function buildcolumns(::Nothing, rowitr::T) where {T}
     state = iterate(rowitr)
     state === nothing && return NamedTuple()
-    row::eltype(rowitr), st = state
+    row, st = state
     names = propertynames(row)
     L = Base.IteratorSize(T)
     len = haslength(L) ? length(rowitr) : 0
diff --git a/src/namedtuples.jl b/src/namedtuples.jl
index 06ccf26..d264449 100644
--- a/src/namedtuples.jl
+++ b/src/namedtuples.jl
@@ -36,7 +36,7 @@ function Base.iterate(rows::NamedTupleIterator{Schema{names, T}}, st=()) where {
 end
 
 # unknown schema case
-function Base.iterate(rows::NamedTupleIterator{nothing, T}, st=()) where {T}
+function Base.iterate(rows::NamedTupleIterator{Nothing, T}, st=()) where {T}
     x = iterate(rows.x, st...)
     x === nothing && return nothing
     row, st = x
diff --git a/test/runtests.jl b/test/runtests.jl
index 185a839..5180c43 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -89,7 +89,7 @@ end
     rt = [(a=1, b=4.0, c="7"), (a=2.0, b=missing, c="8"), (a=3, b=6.0, c="9")]
     @test isequal(Tables.buildcolumns(nothing, rt), (a = Real[1, 2.0, 3], b = Union{Missing, Float64}[4.0, missing, 6.0], c = ["7", "8", "9"]))
 
-    nti = Tables.NamedTupleIterator{nothing, typeof(rt)}(rt)
+    nti = Tables.NamedTupleIterator{Nothing, typeof(rt)}(rt)
     nti2 = collect(nti)
     @test isequal(rt, nti2)
 
@@ -183,9 +183,9 @@ end
     rt = (a = Real[1, 2.0, 3], b = Union{Missing, Float64}[4.0, missing, 6.0], c = ["7", "8", "9"])
 
     dv = Tables.datavaluerows(rt)
-    @test eltype(dv) == NamedTuple{(:a, :b, :c),Tuple{DataValue{Real},DataValue{Float64},DataValue{String}}}
+    @test eltype(dv) == NamedTuple{(:a, :b, :c),Tuple{Real,DataValue{Float64},String}}
     rt2 = collect(dv)
-    @test rt2[1] == (a = DataValue{Real}(1), b = DataValue{Float64}(4.0), c = DataValue{String}("7"))
+    @test rt2[1] == (a = 1, b = DataValue{Float64}(4.0), c = "7")
 
     ei = QueryOperators.EnumerableIterable{eltype(dv), typeof(dv)}(dv)
     nt = ei |> columntable
@@ -193,9 +193,13 @@ end
     rt3 = ei |> rowtable
     @test isequal(rt |> rowtable, rt3)
 
-    rt = [(a=1, b=4.0, c="7"), (a=2, b=5.0, c="8"), (a=3, b=6.0, c="9")]
-    map(source::Enumerable, f::Function, f_expr::Expr)
-    mt = ei |> y->QueryOperators.map(y, x->(a=x.a, c=x.c), Expr(:block))
+    # rt = [(a=1, b=4.0, c="7"), (a=2, b=5.0, c="8"), (a=3, b=6.0, c="9")]
+    mt = ei |> y->QueryOperators.map(y, x->(a=x.b, c=x.c), Expr(:block))
     @inferred (mt |> columntable)
     @inferred (mt |> rowtable)
+
+    # uninferrable case
+    mt = ei |> y->QueryOperators.map(y, x->(a=x.a, c=x.c), Expr(:block))
+    @test (mt |> columntable) == (a = Real[1, 2.0, 3], c = ["7", "8", "9"])
+    @test length(mt |> rowtable) == 3
 end
\ No newline at end of file