Druid: generate correct count clause for HLL fields (#11039)

modules/drivers/druid/src/metabase/driver/druid/query_processor.clj

@@ -608,7 +608,11 @@
   ([output-name]
    {:type :count, :name output-name})
   ([field output-name]
-   (ag:filtered (filter:not (filter:nil? field)) (ag:count output-name))))
+   (if (isa? (:base-type field) :type/DruidHyperUnique)
+     {:type      :hyperUnique
+      :name      output-name
+      :fieldName (->rvalue field)}
+     (ag:filtered (filter:not (filter:nil? field)) (ag:count output-name)))))
 
 (defn- ag:countWhere
   [pred output-name]

modules/drivers/druid/test/metabase/driver/druid_test.clj

@@ -456,3 +456,16 @@
      :breakout   [$venue_category_name $user_name]
      :order-by   [[:asc [:aggregation 0]] [:asc $checkins.venue_category_name]]
      :limit      5}))
+
+;; Do we generate the correct count clause for HLL fields?
+(datasets/expect-with-driver :druid
+  [["Bar" "Szymon Theutrich" 13]
+   ["Mexican" "Dwight Gresham" 12]
+   ["American" "Spiros Teofil" 10]
+   ["Bar" "Felipinho Asklepios" 10]
+   ["Bar" "Kaneonuskatew Eiran" 10]]
+  (druid-query-returning-rows
+    {:aggregation [[:aggregation-options [:count $checkins.user_name] {:name "__count_0"}]]
+     :breakout   [$venue_category_name $user_name]
+     :order-by   [[:desc [:aggregation 0]] [:asc $checkins.venue_category_name]]
+     :limit      5}))

modules/drivers/druid/test/metabase/test/data/druid.clj

@@ -70,7 +70,9 @@
                                                                       :format :auto}
                                                      :dimensionsSpec {:dimensions ["id"
                                                                                    "user_last_login"
-                                                                                   "user_name"
+                                                                                   {:name "user_name"
+                                                                                    :type "string"
+                                                                                    :isInputHyperUnique true}
                                                                                    "user_password"
                                                                                    "venue_category_name"
                                                                                    {:name "venue_latitude"