2023-09-08 clara | Clojure Slack Archive

clara

Joel 2023-09-08T17:40:01.766869Z

Using Accumulators can I use (take … to limit the number of matches? I’m wanting to process a given number of matches multithread on those and then not have to process the matches later. So say 15 matches, I want to process 10 at a time, I want to (take 10) but only get the remaining 5 in another firing of the rule. If I need to let the rules quiesce and do this “outside of the session” that could work as well.

ethanc 2023-09-10T02:59:46.972899Z

The take x accumulator is quite doable with clara today, looking something like:

(defn take-accum
  [x]
  (acc/accum
    {:initial-value nil
     :reduce-fn (fn [items value]
                  (if (= (count items) x)
                    items
                    (conj items value)))}))

However, this doesn’t address: > I want to process 10 at a time, I want to (take 10) but only get the remaining 5 in another firing of the rule. As the accumulator above would be done after accumulating the prerequisite amount of facts. Additional fire-rules wouldn’t propagate new facts after the number was reached. Off the top of my head i don’t know that the latter functionality/ability would be possible within the session itself. As it feels like the remaining 5 would be “unfinished” work for the session, in the sense that fire-rules contract is that after the call, the session should have reached a “steady state”… remaining work would imply a non-stable state.

Joel 2023-09-10T04:05:19.809239Z

That’s what I suspected w/o trying it out. I suppose I could do this outside of the session. Fetch all the matches, and then retract the ones I decide to process.

ethanc 2023-09-12T21:58:05.067689Z

Im always weary of using retract as it feels like re-writing history, probably just a me thing though. As a possible alternative, a partitioning accum:

(defn partitioning-accum
  [x]
  (acc/accum
    {:initial-value nil
     :reduce-fn conj
     :convert-return-fn #(partition-all x %)}))

With perhaps a paging like system:

(r/defrule paging-rule
  [?pages <- (partitioning-accum 3) :from [Long]]
  =>
  (r/insert-all! (map-indexed #(with-meta {:values %2 :page %1} {:type :paged-long}) ?pages)))

Where the pages could be directly queried:

(r/defquery paged-response
  [:?page]
  [:paged-long [{:keys [page values]}] (= page ?page) (= values ?results)])

or gated by processing-requests:

(r/defrule page-processing-rule
  [:process-request [{:keys [page]}] (= ?page page)]
  [:paged-long [{:keys [page values]}] (= page ?page) (= values ?results)]
  =>
  (r/insert! ^{:type :more-processing} {:res ?results}))

Is probably how i’d look at it.

ethanc 2023-09-12T21:58:21.744079Z

apologies for the delay here

Joel 2023-09-10T19:28:27.626829Z

Maybe another option is to pull all of them, process 10, retract 15, then push the 5 back?

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