DB migration to eliminate some null fields in old downloads

The DownloadProvider now ensures that current bytes, total bytes,
title and description are never null in the DB.  Some new code relies
on this assumption for simplicity.  That means we need to ensure this
invariant is true for pre-existing downloads as well.

Change-Id: Iea2289516d2636edf3394678ab08aa9cea31dc69

1 files changed, 28 insertions, 1 deletions

diff --git a/src/com/android/providers/downloads/DownloadProvider.java b/src/com/android/providers/downloads/DownloadProvider.java
index 26065015..2cbf7fbb 100644
--- a/src/com/android/providers/downloads/DownloadProvider.java
+++ b/src/com/android/providers/downloads/DownloadProvider.java
@@ -57,7 +57,7 @@ public final class DownloadProvider extends ContentProvider {
     /** Database filename */
     private static final String DB_NAME = "downloads.db";
     /** Current database version */
-    private static final int DB_VERSION = 104;
+    private static final int DB_VERSION = 105;
     /** Name of table in the database */
     private static final String DB_TABLE = "downloads";
 
@@ -228,12 +228,38 @@ public final class DownloadProvider extends ContentProvider {
                             "INTEGER NOT NULL DEFAULT 0");
                     break;
 
+                case 105:
+                    fillNullValues(db);
+                    break;
+
                 default:
                     throw new IllegalStateException("Don't know how to upgrade to " + version);
             }
         }
 
         /**
+         * insert() now ensures these four columns are never null for new downloads, so this method
+         * makes that true for existing columns, so that code can rely on this assumption.
+         */
+        private void fillNullValues(SQLiteDatabase db) {
+            ContentValues values = new ContentValues();
+            values.put(Downloads.Impl.COLUMN_CURRENT_BYTES, 0);
+            fillNullValuesForColumn(db, values);
+            values.put(Downloads.Impl.COLUMN_TOTAL_BYTES, -1);
+            fillNullValuesForColumn(db, values);
+            values.put(Downloads.Impl.COLUMN_TITLE, "");
+            fillNullValuesForColumn(db, values);
+            values.put(Downloads.Impl.COLUMN_DESCRIPTION, "");
+            fillNullValuesForColumn(db, values);
+        }
+
+        private void fillNullValuesForColumn(SQLiteDatabase db, ContentValues values) {
+            String column = values.valueSet().iterator().next().getKey();
+            db.update(DB_TABLE, values, column + " is null", null);
+            values.clear();
+        }
+
+        /**
          * Set all existing downloads to the cache partition to be invisible in the downloads UI.
          */
         private void makeCacheDownloadsInvisible(SQLiteDatabase db) {
@@ -463,6 +489,7 @@ public final class DownloadProvider extends ContentProvider {
         copyStringWithDefault(Downloads.Impl.COLUMN_TITLE, values, filteredValues, "");
         copyStringWithDefault(Downloads.Impl.COLUMN_DESCRIPTION, values, filteredValues, "");
         filteredValues.put(Downloads.Impl.COLUMN_TOTAL_BYTES, -1);
+        filteredValues.put(Downloads.Impl.COLUMN_CURRENT_BYTES, 0);
 
         if (values.containsKey(Downloads.Impl.COLUMN_IS_VISIBLE_IN_DOWNLOADS_UI)) {
             copyBoolean(Downloads.Impl.COLUMN_IS_VISIBLE_IN_DOWNLOADS_UI, values, filteredValues);