Check for subtasks before using recursive query

app/src/main/java/com/todoroo/astrid/dao/TaskDao.java

@@ -6,6 +6,7 @@
 
 package com.todoroo.astrid.dao;
 
+import static com.todoroo.andlib.utility.AndroidUtilities.atLeastLollipop;
 import static com.todoroo.andlib.utility.DateUtilities.now;
 
 import android.database.Cursor;
@@ -17,6 +18,7 @@ import androidx.room.Transaction;
 import androidx.room.Update;
 import androidx.sqlite.db.SimpleSQLiteQuery;
 import androidx.sqlite.db.SupportSQLiteDatabase;
+import com.google.common.base.Function;
 import com.google.common.base.Joiner;
 import com.todoroo.andlib.sql.Criterion;
 import com.todoroo.andlib.sql.Functions;
@@ -130,8 +132,9 @@ public abstract class TaskDao {
   public abstract int clearCompletedCalendarEvents();
 
   @Transaction
-  public List<TaskContainer> fetchTasks(List<String> queries) {
+  public List<TaskContainer> fetchTasks(Function<Boolean, List<String>> getQueries) {
     long start = BuildConfig.DEBUG ? now() : 0;
+    List<String> queries = getQueries.apply(atLeastLollipop() && hasSubtasks());
     SupportSQLiteDatabase db = database.getOpenHelper().getWritableDatabase();
     int last = queries.size() - 1;
     for (int i = 0 ; i < last ; i++) {
@@ -145,6 +148,13 @@ public abstract class TaskDao {
   @RawQuery
   abstract List<TaskContainer> fetchTasks(SimpleSQLiteQuery query);
 
+  @Query(
+      "SELECT EXISTS("
+          + "SELECT 1 FROM google_tasks WHERE gt_parent > 0 AND gt_deleted = 0"
+          + " UNION ALL "
+          + "SELECT 1 FROM caldav_tasks WHERE cd_parent > 0 AND cd_deleted = 0);")
+  public abstract boolean hasSubtasks();
+
   @Query("UPDATE tasks SET modified = datetime('now', 'localtime') WHERE _id in (:ids)")
   public abstract void touch(List<Long> ids);
 

app/src/main/java/org/tasks/ui/TaskListViewModel.java

@@ -2,8 +2,6 @@ package org.tasks.ui;
 
 import static com.google.common.collect.Lists.newArrayList;
 import static com.todoroo.andlib.sql.Field.field;
-import static com.todoroo.andlib.utility.AndroidUtilities.assertMainThread;
-import static com.todoroo.andlib.utility.AndroidUtilities.atLeastLollipop;
 import static com.todoroo.astrid.activity.TaskListFragment.CALDAV_METADATA_JOIN;
 import static com.todoroo.astrid.activity.TaskListFragment.GTASK_METADATA_JOIN;
 import static com.todoroo.astrid.activity.TaskListFragment.TAGS_METADATA_JOIN;
@@ -102,10 +100,10 @@ public class TaskListViewModel extends ViewModel {
     tasks.observe(owner, observer);
   }
 
-  public static List<String> getQuery(Preferences preferences, Filter filter) {
+  public static List<String> getQuery(Preferences preferences, Filter filter, boolean subtasks) {
     List<Field> fields = newArrayList(TASKS, GTASK, CALDAV, GEOFENCE, PLACE);
 
-    if (atLeastLollipop()
+    if (subtasks
         && filter.supportsSubtasks()
         && !(preferences.isManualSort() && filter.supportsManualSort())) {
       String tagQuery =
@@ -274,11 +272,9 @@ public class TaskListViewModel extends ViewModel {
   }
 
   public void invalidate() {
-    assertMainThread();
-
-    List<String> queries = getQuery(preferences, filter);
     disposable.add(
-        Single.fromCallable(() -> taskDao.fetchTasks(queries))
+        Single.fromCallable(
+                () -> taskDao.fetchTasks(hasSubtasks -> getQuery(preferences, filter, hasSubtasks)))
             .subscribeOn(Schedulers.io())
             .observeOn(AndroidSchedulers.mainThread())
             .subscribe(tasks::postValue, Timber::e));

app/src/main/java/org/tasks/widget/ScrollableViewsFactory.java

@@ -82,7 +82,7 @@ class ScrollableViewsFactory implements RemoteViewsService.RemoteViewsFactory {
   @Override
   public void onDataSetChanged() {
     updateSettings();
-    tasks = taskDao.fetchTasks(getQuery(filter));
+    tasks = taskDao.fetchTasks(hasSubtasks -> getQuery(filter, hasSubtasks));
   }
 
   @Override
@@ -196,7 +196,7 @@ class ScrollableViewsFactory implements RemoteViewsService.RemoteViewsFactory {
     return position < tasks.size() ? tasks.get(position) : null;
   }
 
-  private List<String> getQuery(Filter filter) {
+  private List<String> getQuery(Filter filter, boolean hasSubtasks) {
     AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);
     RemoteViews rv = new RemoteViews(context.getPackageName(), R.layout.scrollable_widget);
     rv.setTextViewText(R.id.widget_title, filter.listingTitle);
@@ -204,7 +204,7 @@ class ScrollableViewsFactory implements RemoteViewsService.RemoteViewsFactory {
       rv.setInt(R.id.widget, "setLayoutDirection", Locale.getInstance(context).getDirectionality());
     }
     appWidgetManager.partiallyUpdateAppWidget(widgetId, rv);
-    List<String> queries = TaskListViewModel.getQuery(preferences, filter);
+    List<String> queries = TaskListViewModel.getQuery(preferences, filter, hasSubtasks);
     int last = queries.size() - 1;
     queries.set(last, subtasksHelper.applySubtasksToWidgetFilter(filter, queries.get(last)));
     return queries;