Let an app opt out of row estimate hints

server/src/instant/db/datalog.clj

@@ -1963,10 +1963,11 @@
        (contains? (flags/flag :always-materialize-attr-ids)
                   (first (uspec/tagged-unwrap (:a named-p))))))
 
-(defn enable-row-hints? [query-hash]
+(defn enable-row-hints? [app-id query-hash]
   (and (or (flags/toggled? :enable-row-hints-globally true)
            (coll/exists? (fn [h] (= query-hash h))
                          (flags/flag :enable-row-hints-query-hashes)))
+       (not (contains? (flags/flag :disable-row-hints-apps) app-id))
        (not (coll/exists? (fn [h] (= query-hash h))
                           (flags/flag :disable-row-hints-query-hashes)))))
 
@@ -2875,7 +2876,7 @@
 
                  :pg-hints (if (flags/toggled? :disable-pg-hints)
                              []
-                             (if (enable-row-hints? (:query-hash ctx))
+                             (if (enable-row-hints? app-id (:query-hash ctx))
                                pg-hints
                                (filterv (fn [hint]
                                           (not= :'Rows (first hint)))

server/src/instant/flags.clj

@@ -237,6 +237,7 @@
                   (update :use-reactive-cache-for-verify-token-apps parse-uuids-flag)
                   (update :backup-skip-app-ids parse-uuids-flag)
                   (update :pkey-null-padding-apps parse-uuids-flag)
+                  (update :disable-row-hints-apps parse-uuids-flag)
                   (update :query-circuit-breaker parse-query-circuit-breaker-flag))
         handle-receive-timeout (reduce (fn [acc {:strs [appId timeoutMs]}]
                                          (assoc acc (parse-uuid appId) timeoutMs))

server/test/instant/db/row_hints_flag_test.clj

@@ -0,0 +1,49 @@
+(ns instant.db.row-hints-flag-test
+  (:require [clojure.test :refer [deftest is testing]]
+            [instant.db.attr-sketch :as cms]
+            [instant.db.datalog :as d]
+            [instant.db.instaql :as iq]
+            [instant.db.model.attr :as attr-model]
+            [instant.flags :as flags]
+            [instant.util.instaql :as instaql-util]))
+
+(def app-id #uuid "5a0c1d2e-7b3f-4c6a-9e8d-1f2a3b4c5d6e")
+
+(def attrs
+  (attr-model/wrap-attrs
+   (mapv (fn [n field]
+           (cond-> {:id (java.util.UUID. 0 n)
+                    :forward-identity [(java.util.UUID. 1 n) "prices" field]
+                    :value-type :blob :cardinality :one
+                    :index? (= field "modified") :unique? (= field "id")}
+             (= field "modified") (assoc :checked-data-type :number)))
+         [1 2 3] ["id" "modified" "value"])))
+
+(def query
+  {:prices {:$ {:where {:and [{:modified {:$gt 100}} {:modified {:$lte 200}}]}
+                :order {:modified "asc"} :first 50}}})
+
+(defn row-hints [app-id]
+  (let [normalized (instaql-util/normalized-forms query)
+        ctx {:app-id app-id :attrs attrs
+             :query-normalized normalized
+             :query-hash (hash normalized)
+             :sketches (into {} (map (fn [a]
+                                       [{:app-id app-id :attr-id (:id a)}
+                                        {:sketch (assoc (cms/make-sketch) :total 240000)}])
+                                     attrs))}
+        patterns (:patterns (iq/instaql-query->patterns ctx query))
+        named (d/annotate-with-hints-impl ctx {} (d/nested->named-patterns patterns))]
+    (binding [d/*enable-pg-hints* true]
+      (->> (d/nested-match-query ctx :m- app-id named)
+           :query
+           :pg-hints
+           (filter #(= :'Rows (first %)))))))
+
+(deftest row-hints-can-be-disabled-per-app
+  (is (seq (row-hints app-id)))
+  (binding [flags/*flag-overrides* {:disable-row-hints-apps #{app-id}}]
+    (testing "the listed app loses only its row hints"
+      (is (empty? (row-hints app-id))))
+    (testing "other apps keep theirs"
+      (is (seq (row-hints (random-uuid)))))))