Make sure auto binning always has at least one bin (#20978)

src/metabase/query_processor/middleware/binning.clj

@@ -63,9 +63,12 @@
 
 (s/defn ^:private calculate-num-bins :- su/IntGreaterThanZero
   "Calculate number of bins of width `bin-width` required to cover interval [`min-value`, `max-value`]."
-  [min-value :- s/Num, max-value :- s/Num, bin-width :- (s/constrained s/Num (complement neg?) "number >= 0")]
-  (long (Math/ceil (/ (- max-value min-value)
-                      bin-width))))
+  [min-value :- s/Num
+   max-value :- s/Num
+   bin-width :- (s/constrained s/Num (complement neg?) "number >= 0")]
+  (max (long (Math/ceil (/ (- max-value min-value)
+                           bin-width)))
+       1))
 
 (s/defn ^:private resolve-default-strategy :- [(s/one (s/enum :bin-width :num-bins) "strategy")
                                                (s/one {:bin-width s/Num, :num-bins su/IntGreaterThanZero} "opts")]

test/metabase/query_processor/middleware/binning_test.clj

@@ -2,7 +2,9 @@
   (:require [clojure.test :refer :all]
             [metabase.models.card :refer [Card]]
             [metabase.models.field :as field :refer [Field]]
+            [metabase.query-processor :as qp]
             [metabase.query-processor.middleware.binning :as binning]
+            [metabase.sync :as sync]
             [metabase.test :as mt]
             [metabase.util :as u]))
 
@@ -150,3 +152,25 @@
                  :breakout     [[:field "PRICE" {:base-type :type/Float, :binning {:strategy :default}}]]
                  :aggregation  [[:count]]})
               (mt/formatted-rows [int int]))))))
+
+(mt/defdataset single-row
+  [["t" [{:field-name    "lat"
+          :base-type     :type/Decimal
+          :semantic-type :type/Latitude}
+         {:field-name    "lon"
+          :base-type     :type/Decimal
+          :semantic-type :type/Longitude}]
+    [[-27.137453079223633 -52.5982666015625]]]])
+
+(deftest auto-bin-single-row-test
+  (testing "Make sure we can auto-bin a Table that only has a single row (#13914)"
+    (mt/dataset single-row
+      ;; sync the Database so we have valid fingerprints for our columns.
+      (sync/sync-database! (mt/db))
+      (let [query (mt/mbql-query t
+                    {:breakout    [[:field %lat {:binning {:strategy :default}}]
+                                   [:field %lon {:binning {:strategy :default}}]]
+                     :aggregation [[:count]]})]
+        (mt/with-native-query-testing-context query
+          (is (= [[-30.00M -60.00M 1]]
+                 (mt/rows (qp/process-query query)))))))))

test/metabase/test/data/interface.clj

@@ -408,7 +408,7 @@
 ;; TODO - not sure everything below belongs in this namespace
 
 (s/defn ^:private dataset-field-definition :- ValidFieldDefinition
-  [{:keys [coercion-strategy base-type] :as field-definition-map} :- DatasetFieldDefinition]
+  [field-definition-map :- DatasetFieldDefinition]
   "Parse a Field definition (from a `defdatset` form or EDN file) and return a FieldDefinition instance for
   comsumption by various test-data-loading methods."
   ;; if definition uses a coercion strategy they need to provide the effective-type