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Fix an N^2 in batch hydration #172

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Fix an N^2 in batch hydration #172

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59 changes: 20 additions & 39 deletions src/toucan2/tools/hydrate.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -430,48 +430,29 @@
;;; `:needs-hydration?`, replace it with the first hydrated instance; repeat this process until we have spliced all
;;; the hydrated instances back in.

(defn- merge-hydrated-instances
"Merge the annotated instances as returned by [[annotate-instances]] and the hydrated instances as returned
by [[hydrate-annotated-instances]] back into a single un-annotated sequence.

(merge-hydrated-instances
[{:needs-hydration? false, :instance {:x 1, :y 1}}
{:needs-hydration? false, :instance {:x 2, :y 2}}
{:needs-hydration? true, :instance {:x 3}}
{:needs-hydration? true, :instance {:x 4}}
{:needs-hydration? false, :instance {:x 5, :y 5}}
{:needs-hydration? true, :instance {:x 6}}]
[{:x 3, :y 3} {:x 4, :y 4} {:x 6, :y 6}])
=>
[{:x 1, :y 1}
{:x 2, :y 2}
{:x 3, :y 3}
{:x 4, :y 4}
{:x 5, :y 5}
{:x 6, :y 6}]"
[annotated-instances hydrated-instances]
(loop [acc [], annotated-instances annotated-instances, hydrated-instances hydrated-instances]
(if (empty? hydrated-instances)
(concat acc (map :instance annotated-instances))
(let [[not-hydrated [_needed-hydration & more]] (split-with (complement :needs-hydration?) annotated-instances)]
(recur (vec (concat acc (map :instance not-hydrated) [(first hydrated-instances)]))
more
(rest hydrated-instances))))))

(defn- annotate-instances [model k instances]
(for [instance instances]
{:needs-hydration? (needs-hydration? model k instance)
:instance instance}))

(defn- hydrate-annotated-instances [model k annotated-instances]
(when-let [instances-that-need-hydration (not-empty (map :instance (filter :needs-hydration? annotated-instances)))]
(batched-hydrate model k instances-that-need-hydration)))
(defn- index-instances-needing-hydration
"Given a list of instances, return a list of the same length and order where each element is a tuple `[i instance]`.
For instances that need hydration, `i` represents the serial number of instances needing hydration. For instances that
don't need hydration, `i` is nil."
[model k instances]
(let [idx (volatile! -1)]
(mapv (fn [instance]
[(when (needs-hydration? model k instance)
(vswap! idx inc))
instance])
instances)))

(m/defmethod hydrate-with-strategy ::multimethod-batched
[model _strategy k instances]
(let [annotated-instances (annotate-instances model k instances)
hydrated-instances (hydrate-annotated-instances model k annotated-instances)]
(merge-hydrated-instances annotated-instances hydrated-instances)))
(let [indexed (index-instances-needing-hydration model k instances)
instances-to-hydrate (not-empty (map second (filter first indexed))) ;; Important: keep doesn't work here.
hydrated-instances (when instances-to-hydrate
(vec (batched-hydrate model k instances-to-hydrate)))]
(mapv (fn [[i unhydrated-instance]]
(if i
(nth hydrated-instances i)
unhydrated-instance))
indexed)))


;;; Method-Based Simple Hydration (using impls of [[simple-hydrate]])
Expand Down
40 changes: 16 additions & 24 deletions test/toucan2/tools/hydrate_test.clj
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Original file line number Diff line number Diff line change
@@ -1,6 +1,5 @@
(ns toucan2.tools.hydrate-test
(:require
[clojure.math.combinatorics :as math.combo]
[clojure.test :refer :all]
[methodical.core :as m]
[toucan2.connection :as conn]
Expand Down Expand Up @@ -352,29 +351,22 @@
(is (= {:f [:a 100]}
(hydrate/hydrate {:f [:a 100]} :p)))))

(deftest ^:parallel merge-hydrated-instances-test
(doseq [[a b c d e f :as order] (take 1 (math.combo/permutations (range 1 7)))
:let [annotated-instances (map (fn [i]
(case (long i)
1 {:needs-hydration? false, :instance {:x 1, :y 1}}
2 {:needs-hydration? false, :instance {:x 2, :y 2}}
3 {:needs-hydration? true, :instance {:x 3}}
4 {:needs-hydration? true, :instance {:x 4}}
5 {:needs-hydration? false, :instance {:x 5, :y 5}}
6 {:needs-hydration? true, :instance {:x 6}}))
order)
hydrated-instances (->> order
(filter #{3 4 6})
(map (fn [i]
{:x i, :y i})))]]
(testing (pr-str order)
(is (= [{:x a, :y a}
{:x b, :y b}
{:x c, :y c}
{:x d, :y d}
{:x e, :y e}
{:x f, :y f}]
(#'hydrate/merge-hydrated-instances annotated-instances hydrated-instances))))))
(deftest ^:synchronized index-instances-needing-hydration-test
(let [instances [{:x 1, :y 1}
{:x 2, :y 2}
{:x 3}
{:x 4}
{:x 5, :y 5}
{:x 6}]]
(with-redefs [hydrate/needs-hydration? (fn [_ _ instance]
(= (count instance) 1))]
(is (= [[nil {:x 1, :y 1}]
[nil {:x 2, :y 2}]
[0 {:x 3}]
[1 {:x 4}]
[nil {:x 5, :y 5}]
[2 {:x 6}]]
(#'hydrate/index-instances-needing-hydration nil nil instances))))))

(m/defmethod hydrate/batched-hydrate [:default ::is-bird?]
[_model _k rows]
Expand Down
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