Replace db count query in user signup process (#18072)

store/opentracinglayer/opentracinglayer.go

@@ -10356,6 +10356,24 @@ func (s *OpenTracingLayerUserStore) InvalidateProfilesInChannelCacheByUser(userI
 
 }
 
+func (s *OpenTracingLayerUserStore) IsEmpty() (bool, error) {
+	origCtx := s.Root.Store.Context()
+	span, newCtx := tracing.StartSpanWithParentByContext(s.Root.Store.Context(), "UserStore.IsEmpty")
+	s.Root.Store.SetContext(newCtx)
+	defer func() {
+		s.Root.Store.SetContext(origCtx)
+	}()
+
+	defer span.Finish()
+	result, err := s.UserStore.IsEmpty()
+	if err != nil {
+		span.LogFields(spanlog.Error(err))
+		ext.Error.Set(span, true)
+	}
+
+	return result, err
+}
+
 func (s *OpenTracingLayerUserStore) PermanentDelete(userID string) error {
 	origCtx := s.Root.Store.Context()
 	span, newCtx := tracing.StartSpanWithParentByContext(s.Root.Store.Context(), "UserStore.PermanentDelete")

store/retrylayer/retrylayer.go

@@ -11236,6 +11236,26 @@ func (s *RetryLayerUserStore) InvalidateProfilesInChannelCacheByUser(userID stri
 
 }
 
+func (s *RetryLayerUserStore) IsEmpty() (bool, error) {
+
+	tries := 0
+	for {
+		result, err := s.UserStore.IsEmpty()
+		if err == nil {
+			return result, nil
+		}
+		if !isRepeatableError(err) {
+			return result, err
+		}
+		tries++
+		if tries >= 3 {
+			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
+			return result, err
+		}
+	}
+
+}
+
 func (s *RetryLayerUserStore) PermanentDelete(userID string) error {
 
 	tries := 0

store/sqlstore/user_store.go

@@ -2002,3 +2002,13 @@ func (us SqlUserStore) GetKnownUsers(userId string) ([]string, error) {
 
 	return userIds, nil
 }
+
+// IsEmpty returns whether or not the Users table is empty.
+func (us SqlUserStore) IsEmpty() (bool, error) {
+	var hasRows bool
+	err := us.GetReplica().SelectOne(&hasRows, `SELECT EXISTS (SELECT 1 FROM Users)`)
+	if err != nil {
+		return false, errors.Wrap(err, "failed to check if table is empty")
+	}
+	return !hasRows, nil
+}

store/store.go

@@ -424,6 +424,7 @@ type UserStore interface {
 	DeactivateGuests() ([]string, error)
 	AutocompleteUsersInChannel(teamID, channelID, term string, options *model.UserSearchOptions) (*model.UserAutocompleteInChannel, error)
 	GetKnownUsers(userID string) ([]string, error)
+	IsEmpty() (bool, error)
 }
 
 type BotStore interface {

store/storetest/mocks/UserStore.go

@@ -1038,6 +1038,27 @@ func (_m *UserStore) InvalidateProfilesInChannelCacheByUser(userID string) {
 	_m.Called(userID)
 }
 
+// IsEmpty provides a mock function with given fields:
+func (_m *UserStore) IsEmpty() (bool, error) {
+	ret := _m.Called()
+
+	var r0 bool
+	if rf, ok := ret.Get(0).(func() bool); ok {
+		r0 = rf()
+	} else {
+		r0 = ret.Get(0).(bool)
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func() error); ok {
+		r1 = rf()
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // PermanentDelete provides a mock function with given fields: userID
 func (_m *UserStore) PermanentDelete(userID string) error {
 	ret := _m.Called(userID)

store/storetest/user_store.go

@@ -36,6 +36,7 @@ func TestUserStore(t *testing.T, ss store.Store, s SqlStore) {
 		require.NoError(t, err, "failed cleaning up test user %s", u.Username)
 	}
 
+	t.Run("IsEmpty", func(t *testing.T) { testIsEmpty(t, ss) })
 	t.Run("Count", func(t *testing.T) { testCount(t, ss) })
 	t.Run("AnalyticsActiveCount", func(t *testing.T) { testUserStoreAnalyticsActiveCount(t, ss, s) })
 	t.Run("AnalyticsActiveCountForPeriod", func(t *testing.T) { testUserStoreAnalyticsActiveCountForPeriod(t, ss, s) })
@@ -5711,3 +5712,28 @@ func testGetKnownUsers(t *testing.T, ss store.Store) {
 		assert.ElementsMatch(t, userIds, []string{u2.Id, u3.Id})
 	})
 }
+
+func testIsEmpty(t *testing.T, ss store.Store) {
+	ok, err := ss.User().IsEmpty()
+	require.NoError(t, err)
+	require.True(t, ok)
+
+	u := model.User{
+		Email:    MakeEmail(),
+		Username: model.NewId(),
+	}
+
+	_, err = ss.User().Save(&u)
+	require.NoError(t, err)
+
+	ok, err = ss.User().IsEmpty()
+	require.NoError(t, err)
+	require.False(t, ok)
+
+	err = ss.User().PermanentDelete(u.Id)
+	require.NoError(t, err)
+
+	ok, err = ss.User().IsEmpty()
+	require.NoError(t, err)
+	require.True(t, ok)
+}

store/timerlayer/timerlayer.go

@@ -9345,6 +9345,22 @@ func (s *TimerLayerUserStore) InvalidateProfilesInChannelCacheByUser(userID stri
 	}
 }
 
+func (s *TimerLayerUserStore) IsEmpty() (bool, error) {
+	start := timemodule.Now()
+
+	result, err := s.UserStore.IsEmpty()
+
+	elapsed := float64(timemodule.Since(start)) / float64(timemodule.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if err == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("UserStore.IsEmpty", success, elapsed)
+	}
+	return result, err
+}
+
 func (s *TimerLayerUserStore) PermanentDelete(userID string) error {
 	start := timemodule.Now()