From 606a7f9a5e340e9f237fbb9f8ef0849a7ce4b711 Mon Sep 17 00:00:00 2001
From: Varun Shah <varunshah@google.com>
Date: Tue, 25 Feb 2020 19:48:13 -0800
Subject: [PATCH] Remove UsageStats files older than 2 years.

As a privacy improvement, do not store usage stats data that is older
than 2 years. Previously, stats were kept for 3 years.

This will also help reduce the storage taken up by stats and improve the
performance of query stats API calls which require files to be read from
disk since the number of files read are significantly less.

Bug: 148524623
Test: atest UsageStatsDatabaseTest
Change-Id: I159914a87ba4137f0f3d869c69abf3b16ae77657
---
 .../android/server/usage/UsageStatsDatabase.java   | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/services/usage/java/com/android/server/usage/UsageStatsDatabase.java b/services/usage/java/com/android/server/usage/UsageStatsDatabase.java
index 361b1c06a6b5b..a8e374f0edc28 100644
--- a/services/usage/java/com/android/server/usage/UsageStatsDatabase.java
+++ b/services/usage/java/com/android/server/usage/UsageStatsDatabase.java
@@ -178,7 +178,12 @@ public class UsageStatsDatabase {
             }
 
             checkVersionAndBuildLocked();
-            indexFilesLocked();
+            // Perform a pruning of older files if there was an upgrade, otherwise do indexing.
+            if (mUpgradePerformed) {
+                prune(currentTimeMillis); // prune performs an indexing when done
+            } else {
+                indexFilesLocked();
+            }
 
             // Delete files that are in the future.
             for (TimeSparseArray<AtomicFile> files : mSortedStatFiles) {
@@ -914,26 +919,31 @@ public class UsageStatsDatabase {
      */
     public void prune(final long currentTimeMillis) {
         synchronized (mLock) {
+            // prune all files older than 2 years in the yearly directory
             mCal.setTimeInMillis(currentTimeMillis);
-            mCal.addYears(-3);
+            mCal.addYears(-2);
             pruneFilesOlderThan(mIntervalDirs[UsageStatsManager.INTERVAL_YEARLY],
                     mCal.getTimeInMillis());
 
+            // prune all files older than 6 months in the monthly directory
             mCal.setTimeInMillis(currentTimeMillis);
             mCal.addMonths(-6);
             pruneFilesOlderThan(mIntervalDirs[UsageStatsManager.INTERVAL_MONTHLY],
                     mCal.getTimeInMillis());
 
+            // prune all files older than 4 weeks in the weekly directory
             mCal.setTimeInMillis(currentTimeMillis);
             mCal.addWeeks(-4);
             pruneFilesOlderThan(mIntervalDirs[UsageStatsManager.INTERVAL_WEEKLY],
                     mCal.getTimeInMillis());
 
+            // prune all files older than 10 days in the weekly directory
             mCal.setTimeInMillis(currentTimeMillis);
             mCal.addDays(-10);
             pruneFilesOlderThan(mIntervalDirs[UsageStatsManager.INTERVAL_DAILY],
                     mCal.getTimeInMillis());
 
+            // prune chooser counts for all usage stats older than the defined period
             mCal.setTimeInMillis(currentTimeMillis);
             mCal.addDays(-SELECTION_LOG_RETENTION_LEN);
             for (int i = 0; i < mIntervalDirs.length; ++i) {