> Please have a look at the following function (explained in the doc
> string). I have a bunch of rows that I need to aggregate using
> different functions per field. I also need to apply the aggregate to a
> subset of the rows. Obviously this is just like SQL aggregation, hence
> the interface I've specified.
>
> However I'm left wondering whether my implementation could be improved.
>
> Particularly I very often find myself doing
>
> (apply hash-map (flatten (for [[k v] some-map] ...)))
>
> so often in fact that I feel like I'm missing something.
>
> Any pointers or advice on improving my style will be much appreciated!
Don't have a direct answer to your question, but what about
implementing aggregate like this -
(defn aggregate [rows & {select :select where :where}]
(let [projection (apply merge-with vector (map #(select-keys %
(keys select)) (filter where rows)))]
(reduce (fn [agg [k v]] (assoc agg k (apply (select k) v))) {}
projection)))
Regards,
BG
--
Baishampayan Ghose
b.ghose at gmail.com
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