Add pruneWork(Sync) methods.

This method will prune work matching the following criteria:
- Finished (succeeded, failed, cancelled)
- Zero unfinished dependents

This, together with cancelAll, gives the ability for people
to clear jobs and solves the "observation of a growing list
of jobs" problem.

Change-Id: Ied5571f3d143659f5d52cc4e1983e96329e91390
Fixes: 79950952
Test: Added and ran tests.

6 files changed, 136 insertions, 0 deletions

diff --git a/work/workmanager/src/androidTest/java/androidx/work/impl/WorkManagerImplTest.java b/work/workmanager/src/androidTest/java/androidx/work/impl/WorkManagerImplTest.java
index 71686008903..a96c677ece4 100644
--- a/work/workmanager/src/androidTest/java/androidx/work/impl/WorkManagerImplTest.java
+++ b/work/workmanager/src/androidTest/java/androidx/work/impl/WorkManagerImplTest.java
@@ -1333,6 +1333,38 @@ public class WorkManagerImplTest {
 
     @Test
     @SmallTest
+    public void pruneFinishedWork() {
+        OneTimeWorkRequest enqueuedWork = new OneTimeWorkRequest.Builder(TestWorker.class).build();
+        OneTimeWorkRequest finishedWork =
+                new OneTimeWorkRequest.Builder(TestWorker.class).setInitialState(SUCCEEDED).build();
+        OneTimeWorkRequest finishedWorkWithUnfinishedDependent =
+                new OneTimeWorkRequest.Builder(TestWorker.class).setInitialState(SUCCEEDED).build();
+        OneTimeWorkRequest finishedWorkWithLongKeepForAtLeast =
+                new OneTimeWorkRequest.Builder(TestWorker.class)
+                        .setInitialState(SUCCEEDED)
+                        .keepResultsForAtLeast(999, TimeUnit.DAYS)
+                        .build();
+
+        insertWorkSpecAndTags(enqueuedWork);
+        insertWorkSpecAndTags(finishedWork);
+        insertWorkSpecAndTags(finishedWorkWithUnfinishedDependent);
+        insertWorkSpecAndTags(finishedWorkWithLongKeepForAtLeast);
+
+        insertDependency(enqueuedWork, finishedWorkWithUnfinishedDependent);
+
+        mWorkManagerImpl.synchronous().pruneWorkSync();
+
+        WorkSpecDao workSpecDao = mDatabase.workSpecDao();
+        assertThat(workSpecDao.getWorkSpec(enqueuedWork.getStringId()), is(notNullValue()));
+        assertThat(workSpecDao.getWorkSpec(finishedWork.getStringId()), is(nullValue()));
+        assertThat(workSpecDao.getWorkSpec(finishedWorkWithUnfinishedDependent.getStringId()),
+                is(notNullValue()));
+        assertThat(workSpecDao.getWorkSpec(finishedWorkWithLongKeepForAtLeast.getStringId()),
+                is(nullValue()));
+    }
+
+    @Test
+    @SmallTest
     public void testSynchronousCancelAndGetStatus() {
         OneTimeWorkRequest work = new OneTimeWorkRequest.Builder(TestWorker.class).build();
         insertWorkSpecAndTags(work);
diff --git a/work/workmanager/src/main/java/androidx/work/SynchronousWorkManager.java b/work/workmanager/src/main/java/androidx/work/SynchronousWorkManager.java
index f01e363152a..9f633d8e3e0 100644
--- a/work/workmanager/src/main/java/androidx/work/SynchronousWorkManager.java
+++ b/work/workmanager/src/main/java/androidx/work/SynchronousWorkManager.java
@@ -21,6 +21,7 @@ import android.support.annotation.WorkerThread;
 
 import java.util.List;
 import java.util.UUID;
+import java.util.concurrent.TimeUnit;
 
 /**
  * Blocking methods for {@link WorkManager} operations.  These methods are expected to be called
@@ -129,6 +130,20 @@ public interface SynchronousWorkManager {
     long getLastCancelAllTimeMillisSync();
 
     /**
+     * Prunes all eligible finished work from the internal database in a synchronous fashion.
+     * Eligible work must be finished ({@link State#SUCCEEDED}, {@link State#FAILED}, or
+     * {@link State#CANCELLED}), with zero unfinished dependents.
+     * <p>
+     * <b>Use this method with caution</b>; by invoking it, you (and any modules and libraries in
+     * your codebase) will no longer be able to observe the {@link WorkStatus} of the pruned work.
+     * You do not normally need to call this method - WorkManager takes care to auto-prune its work
+     * after a sane period of time.  This method also ignores the
+     * {@link OneTimeWorkRequest.Builder#keepResultsForAtLeast(long, TimeUnit)} policy.
+     */
+    @WorkerThread
+    void pruneWorkSync();
+
+    /**
      * Gets the {@link WorkStatus} of a given work id in a synchronous fashion.  This method is
      * expected to be called from a background thread.
      *
diff --git a/work/workmanager/src/main/java/androidx/work/WorkManager.java b/work/workmanager/src/main/java/androidx/work/WorkManager.java
index 83891dccef4..5960e50fcab 100644
--- a/work/workmanager/src/main/java/androidx/work/WorkManager.java
+++ b/work/workmanager/src/main/java/androidx/work/WorkManager.java
@@ -26,6 +26,7 @@ import androidx.work.impl.WorkManagerImpl;
 import java.util.Arrays;
 import java.util.List;
 import java.util.UUID;
+import java.util.concurrent.TimeUnit;
 
 /**
  * WorkManager is a library used to enqueue work that is guaranteed to execute after its constraints
@@ -288,6 +289,19 @@ public abstract class WorkManager {
     public abstract void cancelAllWork();
 
     /**
+     * Prunes all eligible finished work from the internal database.  Eligible work must be finished
+     * ({@link State#SUCCEEDED}, {@link State#FAILED}, or {@link State#CANCELLED}), with zero
+     * unfinished dependents.
+     * <p>
+     * <b>Use this method with caution</b>; by invoking it, you (and any modules and libraries in
+     * your codebase) will no longer be able to observe the {@link WorkStatus} of the pruned work.
+     * You do not normally need to call this method - WorkManager takes care to auto-prune its work
+     * after a sane period of time.  This method also ignores the
+     * {@link OneTimeWorkRequest.Builder#keepResultsForAtLeast(long, TimeUnit)} policy.
+     */
+    public abstract void pruneWork();
+
+    /**
      * Gets a {@link LiveData} of the last time all work was cancelled.  This method is intended for
      * use by library and module developers who have dependent data in their own repository that
      * must be updated or deleted in case someone cancels their work without their prior knowledge.
diff --git a/work/workmanager/src/main/java/androidx/work/impl/WorkManagerImpl.java b/work/workmanager/src/main/java/androidx/work/impl/WorkManagerImpl.java
index 5b659d1c67b..13ba38f3528 100644
--- a/work/workmanager/src/main/java/androidx/work/impl/WorkManagerImpl.java
+++ b/work/workmanager/src/main/java/androidx/work/impl/WorkManagerImpl.java
@@ -43,6 +43,7 @@ import androidx.work.impl.utils.CancelWorkRunnable;
 import androidx.work.impl.utils.ForceStopRunnable;
 import androidx.work.impl.utils.LiveDataUtils;
 import androidx.work.impl.utils.Preferences;
+import androidx.work.impl.utils.PruneWorkRunnable;
 import androidx.work.impl.utils.StartWorkRunnable;
 import androidx.work.impl.utils.StopWorkRunnable;
 import androidx.work.impl.utils.taskexecutor.TaskExecutor;
@@ -340,6 +341,7 @@ public class WorkManagerImpl extends WorkManager implements SynchronousWorkManag
     }
 
     @Override
+    @WorkerThread
     public void cancelUniqueWorkSync(@NonNull String uniqueWorkName) {
         assertBackgroundThread("Cannot cancelAllWorkByNameBlocking on main thread!");
         CancelWorkRunnable.forName(uniqueWorkName, this).run();
@@ -351,6 +353,7 @@ public class WorkManagerImpl extends WorkManager implements SynchronousWorkManag
     }
 
     @Override
+    @WorkerThread
     public void cancelAllWorkSync() {
         assertBackgroundThread("Cannot cancelAllWorkSync on main thread!");
         CancelWorkRunnable.forAll(this).run();
@@ -367,6 +370,18 @@ public class WorkManagerImpl extends WorkManager implements SynchronousWorkManag
     }
 
     @Override
+    public void pruneWork() {
+        mTaskExecutor.executeOnBackgroundThread(new PruneWorkRunnable(this));
+    }
+
+    @Override
+    @WorkerThread
+    public void pruneWorkSync() {
+        assertBackgroundThread("Cannot pruneWork on main thread!");
+        new PruneWorkRunnable(this).run();
+    }
+
+    @Override
     public LiveData<WorkStatus> getStatusById(@NonNull UUID id) {
         WorkSpecDao dao = mWorkDatabase.workSpecDao();
         LiveData<List<WorkSpec.WorkStatusPojo>> inputLiveData =
diff --git a/work/workmanager/src/main/java/androidx/work/impl/model/WorkSpecDao.java b/work/workmanager/src/main/java/androidx/work/impl/model/WorkSpecDao.java
index 7d9775d380f..f08658fb088 100644
--- a/work/workmanager/src/main/java/androidx/work/impl/model/WorkSpecDao.java
+++ b/work/workmanager/src/main/java/androidx/work/impl/model/WorkSpecDao.java
@@ -291,4 +291,17 @@ public interface WorkSpecDao {
                 + ")"
     )
     List<WorkSpec> getEligibleWorkForScheduling();
+
+    /**
+     * Immediately prunes eligible work from the database meeting the following criteria:
+     * - Is finished (succeeded, failed, or cancelled)
+     * - Has zero unfinished dependents
+     */
+    @Query("DELETE FROM workspec WHERE "
+            + "state IN " + COMPLETED_STATES
+            + " AND (SELECT COUNT(*)=0 FROM dependency WHERE "
+            + "    prerequisite_id=id AND "
+            + "    work_spec_id NOT IN "
+            + "        (SELECT id FROM workspec WHERE state IN " + COMPLETED_STATES + "))")
+    void pruneFinishedWorkWithZeroDependentsIgnoringKeepForAtLeast();
 }
diff --git a/work/workmanager/src/main/java/androidx/work/impl/utils/PruneWorkRunnable.java b/work/workmanager/src/main/java/androidx/work/impl/utils/PruneWorkRunnable.java
new file mode 100644
index 00000000000..bf93f4602a6
--- /dev/null
+++ b/work/workmanager/src/main/java/androidx/work/impl/utils/PruneWorkRunnable.java
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.work.impl.utils;
+
+import android.support.annotation.RestrictTo;
+
+import androidx.work.impl.WorkDatabase;
+import androidx.work.impl.WorkManagerImpl;
+import androidx.work.impl.model.WorkSpecDao;
+
+/**
+ * A Runnable that prunes work in the background.  Pruned work meets the following criteria:
+ * - Is finished (succeeded, failed, or cancelled)
+ * - Has zero unfinished dependents
+ *
+ * @hide
+ */
+@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
+public class PruneWorkRunnable implements Runnable {
+
+    private WorkManagerImpl mWorkManagerImpl;
+
+    public PruneWorkRunnable(WorkManagerImpl workManagerImpl) {
+        mWorkManagerImpl = workManagerImpl;
+    }
+
+    @Override
+    public void run() {
+        WorkDatabase workDatabase = mWorkManagerImpl.getWorkDatabase();
+        WorkSpecDao workSpecDao = workDatabase.workSpecDao();
+        workSpecDao.pruneFinishedWorkWithZeroDependentsIgnoringKeepForAtLeast();
+    }
+}