Created
October 21, 2023 02:52
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Aggregate data in the form of a list of hash maps in Clojure. Inspired by SQL GROUP BY and aggregate functions like SUM and MAX
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| (defn aggregate-data | |
| "data - collection of hash-maps to aggregate | |
| group-key - vector of keys to group hash-maps | |
| aggregates - vector of vectors of key, aggregate fn and optionally a new | |
| name for this key e.g. | |
| [[+ :amount :stock] | |
| [max :date :latest-tx-date]] | |
| Aggregate functions receive variable arguments" | |
| [data group-keys aggregates] | |
| (->> data | |
| (group-by (fn [item] (select-keys item group-keys))) | |
| (map (fn [[_group-key items]] | |
| (merge (select-keys (first items) group-keys) | |
| (into {} | |
| (map (fn [[aggregate-fn aggregate-key rename]] | |
| (vector (or rename aggregate-key) | |
| (apply aggregate-fn | |
| (->> (map aggregate-key items) | |
| (remove nil?))))) | |
| aggregates))))))) | |
| ;; usage | |
| (def inventory-txs | |
| [{:id "tx1" | |
| :pid "p1" | |
| :desc "Inventory input Product P1" | |
| :amount 10 | |
| :created 1673308800000} | |
| {:id "tx2" | |
| :pid "p1" | |
| :desc "Inventory output Product P1" | |
| :amount -5 | |
| :created 1674172800000} | |
| {:id "tx3" | |
| :pid "p2" | |
| :desc "Invoice input Product P2" | |
| :amount 8 | |
| :created 1673395200000}]) | |
| (aggregate-data inventory-txs [:pid] | |
| [[+ :amount] | |
| [max :created :latest-tx-date]]) | |
| ;; result | |
| ({:pid "p1", :amount 5, :latest-tx-date 1674172800000} | |
| {:pid "p2", :amount 8, :latest-tx-date 1673395200000}) |
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