Incorporate fast join into Base.join

src/join.jl

@@ -1,10 +1,14 @@
 joinmap = Dict(
-    :JoinInner=>DataFrames.innerjoin,
-    :JoinBoth=>DataFrames.innerjoin,
-    :JoinOuter=>DataFrames.outerjoin,
-    :JoinAll=>DataFrames.outerjoin,
-    :JoinLeft=>DataFrames.leftjoin,
-    :JoinRight=>DataFrames.rightjoin
+    :JoinInner => :inner,
+    :JoinBoth => :inner,
+    :JoinOuter => :outer,
+    :JoinAll => :outer,
+    :JoinLeft => :left,
+    :JoinRight => :right,
+    :outerjoin => :outer,
+    :innerjoin => :inner, 
+    :leftjoin => :left,
+    :rightjoin => :right,
 )
 
 """
@@ -71,6 +75,16 @@ where `jointype` must be one of `:JoinInner`, `:JoinBoth`, `:JoinOuter`, `:JoinA
 
 `cbind` is an alias for `join` method.
 
+## Using the `DataFrames` join methods
+
+DataFrames.jl's join methods are battle-tested, and handle quite a few error cases which `TSFrames.join` may not. 
+In order to use DataFrames' join methods, which are somewhat slower than `TSFrames.join`, you would have to 
+join the TSFrames' internal DataFrames, then construct a new TSFrame.  For `ts1::TSFrame`, `ts2::TSFrame`, 
+this is how you would construct an outer join:
+```julia
+TSFrame(DataFrames.outerjoin(ts1.coredata, ts2.coredata; makeunique = true))
+```
+
 # Examples
 ```jldoctest; setup = :(using TSFrames, DataFrames, Dates, Random, Statistics)
 julia> using Random;
@@ -294,9 +308,9 @@ function Base.join(
     ts...;
     jointype::Symbol=:JoinAll
 )
-    result = joinmap[jointype](ts1.coredata, ts2.coredata, on=:Index, makeunique=true)
+    result = TSFrames.fast_join(ts1.coredata, ts2.coredata; method = joinmap[method])
     for tsf in ts
-        result = joinmap[jointype](result, tsf.coredata, on=:Index, makeunique=true)
+        result = TSFrames.fast_join(result, tsf.coredata; method = joinmap[method])
     end
     return TSFrame(result)
 end
@@ -430,18 +444,6 @@ function fast_join(left::TSFrame, right::TSFrame; method = :outer)
 
 end
 
-function fast_outerjoin(ts1::TSFrame, ts2::TSFrame, others:::TSFrame...)
-
-    result = fast_outerjoin(ts1, ts2)
-
-    for other in others
-        result = fast_outerjoin(ts1, ts2)
-    end
-
-    return result
-
-end
-
 # # as of 22-Jan-22, the timer outputs are as follows:
 # BenchmarkTools.Trial: 100 samples with 1 evaluation.
 #  Range (min … max):  61.627 ms … 287.822 ms  ┊ GC (min … max):  0.00% … 71.47%