Generate unique aliases for operations in aggregations (#30302)

Fixes #30262.

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

@@ -1049,7 +1049,16 @@
          (extract-aggregations (first args) parent-name aggregations-seen)
 
          (aggregation-op op)
-         (let [aggr-name (str parent-name "~" (annotate/aggregation-name aggr-expr))]
+         (let [aliases-taken (set (vals aggregations-seen))
+               aggr-name (annotate/aggregation-name aggr-expr)
+               desired-alias (str parent-name "~" aggr-name)
+               ;; find a free alias by appending increasing integers
+               ;; to the desired alias
+               aggr-name (some (fn [suffix]
+                                 (let [alias (str desired-alias suffix)]
+                                   (when-not (aliases-taken alias)
+                                     alias)))
+                               (cons "" (iterate inc 1)))]
            [(str \$ aggr-name) (assoc aggregations-seen aggr-expr aggr-name)])
 
          :else
@@ -1061,7 +1070,7 @@
      [aggr-expr aggregations-seen])))
 
 (defn- simplify-extracted-aggregations
-  "Simplifies the extracted aggregation ()for `aggr-name` if the expression
+  "Simplifies the extracted aggregation for `aggr-name` if the expression
   contains only a single top-level aggregation. In this case there is no
   need for namespacing and `aggr-name` can be used as the name of the group
   introduced for the aggregation.

test/metabase/query_processor_test/expression_aggregations_test.clj

@@ -143,6 +143,23 @@
                  {:aggregation [[:+ [:max $price] [:min [:- $price $id]]]]
                   :breakout    [$price]})))))))
 
+(deftest integer-aggregation-division-test
+  (testing "division of two sum aggregations (#30262)"
+    (mt/test-drivers (mt/normal-drivers-with-feature :expression-aggregations)
+      (mt/dataset sample-dataset
+        (testing "expression parts not selected"
+          (is (= [[27]]
+                 (mt/formatted-rows [int]
+                   (mt/run-mbql-query orders
+                     {:aggregation [[:/ [:sum $product_id] [:sum $quantity]]]})))))
+        (testing "expression parts also selected"
+         (is (= [[1885900 69540 27]]
+                (mt/formatted-rows [int int int]
+                  (mt/run-mbql-query orders
+                    {:aggregation [[:sum $product_id]
+                                   [:sum $quantity]
+                                   [:/ [:sum $product_id] [:sum $quantity]]]})))))))))
+
 (deftest aggregation-without-field-test
   (mt/test-drivers (mt/normal-drivers-with-feature :expression-aggregations)
     (testing "aggregation w/o field"