This is what I have working, but don't know if there is a better way

(def combined-ds (ds/concat [ds ds]))

(defn merge-vectors-of-maps [vecs]
  (ds/->>dataset (reduce into [] vecs)))

(def merged-ds (merge-vectors-of-maps [(ds/mapseq-reader(first combined-ds)) (ds/mapseq-reader(second combined-ds))]))

(ds/concat ds ds) should work, don't use vector.

(ds/concat ds ds) doesn't work unfortunately. It creates two datasets in the same entity. The code I wrote above does work and I'll stick with it. I don't know what the use case of ds/concat is, but I'll let it go as the functions above get me through.

Strange. ds/concat is exactly what you need. And I have never encountered any problem with it.

@U04A1LVBBPU have you tried (ds/concat-copying ds ds)? Worked locally for me. Note no vector required. However if you need the datasets in a vector try (apply ds/concat-copying [ds ds]) I'm not sure why ds/concat didn't work for you, but as I understand concat-copying it works like a reducer

I verified it on 7.000-beta-38 and it works and gives the same result as your merged-ds . btw. when you call (ds/concat [ds ds]) it just returns [ds ds].

(def ds (ds/->dataset [{"DestinationName" "CZ_1", "ProductName" "FG_1", "Quantity" 100, "Allocated-Qty" 0, "SourceName" "DC_1", :ratio 0.5} {"DestinationName" "CZ_1", "ProductName" "FG_1", "Quantity" 100, "Allocated-Qty" 0, "SourceName" "DC_2", :ratio 0.5}]))

;; => _unnamed [2 6]:
;;    | DestinationName | ProductName | Quantity | Allocated-Qty | SourceName | :ratio |
;;    |-----------------|-------------|---------:|--------------:|------------|-------:|
;;    |            CZ_1 |        FG_1 |      100 |             0 |       DC_1 |    0.5 |
;;    |            CZ_1 |        FG_1 |      100 |             0 |       DC_2 |    0.5 |

(ds/concat ds ds)

;; => _unnamed [4 6]:
;;    | DestinationName | ProductName | Quantity | Allocated-Qty | SourceName | :ratio |
;;    |-----------------|-------------|---------:|--------------:|------------|-------:|
;;    |            CZ_1 |        FG_1 |      100 |             0 |       DC_1 |    0.5 |
;;    |            CZ_1 |        FG_1 |      100 |             0 |       DC_2 |    0.5 |
;;    |            CZ_1 |        FG_1 |      100 |             0 |       DC_1 |    0.5 |
;;    |            CZ_1 |        FG_1 |      100 |             0 |       DC_2 |    0.5 |

(ds/concat-copying ds ds)

;; => _unnamed [4 6]:
;;    | DestinationName | ProductName | Quantity | Allocated-Qty | SourceName | :ratio |
;;    |-----------------|-------------|---------:|--------------:|------------|-------:|
;;    |            CZ_1 |        FG_1 |      100 |             0 |       DC_1 |    0.5 |
;;    |            CZ_1 |        FG_1 |      100 |             0 |       DC_2 |    0.5 |
;;    |            CZ_1 |        FG_1 |      100 |             0 |       DC_1 |    0.5 |
;;    |            CZ_1 |        FG_1 |      100 |             0 |       DC_2 |    0.5 |

Thanks for taking the time to look at this guys. I am sorry, it was my fault putting in (ds/concat [ds ds]) instead of (ds/concat ds ds). genmeblog, you are correct, (ds/concat ds ds) works as expected