Speed up database update

Drop the trigger on sync_id before doing a bulk update of sync_id
fields.  This dramatically reduces the time required for the
calendar database update when there are lots of events.

Bug 5699796

Change-Id: I94c2fb624b5b63bfdf760b3092697f9205a634c9

src/com/android/providers/calendar/CalendarDatabaseHelper.java

@@ -1512,14 +1512,19 @@ void upgradeToVersion306(SQLiteDatabase db) {
         * Change event id's from ".../private/full/... to .../events/...
         * Set Calendars.canPartiallyUpdate to 1 to support partial updates
         * Nuke sync state so we re-sync with a fresh etag and edit url
+        *
+        * We need to drop the original_sync_update trigger because it fires whenever the
+        * sync_id field is touched, and dramatically slows this operation.
         */
+        db.execSQL("DROP TRIGGER IF EXISTS original_sync_update");
         db.execSQL("UPDATE Events SET "
                 + "_sync_id = REPLACE(_sync_id, '/private/full/', '/events/'), "
                 + "original_sync_id = REPLACE(original_sync_id, '/private/full/', '/events/') "
                 + "WHERE _id IN (SELECT Events._id FROM Events "
                 +    "JOIN Calendars ON Events.calendar_id = Calendars._id "
                 +    "WHERE account_type = 'com.google')"
         );
+        db.execSQL(CREATE_SYNC_ID_UPDATE_TRIGGER);
 
         db.execSQL("UPDATE Calendars SET canPartiallyUpdate = 1 WHERE account_type = 'com.google'");