fix migrations, add docs to versions.gradle

Author: yigit

PersistenceMigrationsSample/app/src/room2/java/com/example/android/persistence/migrations/UsersDatabase.java

@@ -67,15 +67,8 @@ public void migrate(SupportSQLiteDatabase database) {
     static final Migration MIGRATION_2_3 = new Migration(2, 3) {
         @Override
         public void migrate(SupportSQLiteDatabase database) {
-            database.execSQL("CREATE TABLE IF NOT EXISTS Users_new ("
-                    + "`userid` INTEGER NOT NULL,"
-                    + "`username` TEXT,"
-                    + "`last_update` INTEGER,"
-                    + "PRIMARY KEY(`userid`))");
-            database.execSQL("INSERT INTO Users_new "
-                    + " SELECT userid, username, null FROM Users");
-            database.execSQL("DROP TABLE Users");
-            database.execSQL("ALTER TABLE Users_new RENAME TO users");
+            database.execSQL("ALTER TABLE Users "
+                    + " ADD COLUMN last_update INTEGER");
         }
     };
 

PersistenceMigrationsSample/app/src/room3/java/com/example/android/persistence/migrations/UsersDatabase.java

@@ -67,15 +67,8 @@ public void migrate(SupportSQLiteDatabase database) {
     static final Migration MIGRATION_2_3 = new Migration(2, 3) {
         @Override
         public void migrate(SupportSQLiteDatabase database) {
-            database.execSQL("CREATE TABLE IF NOT EXISTS Users_new ("
-                    + "`userid` INTEGER NOT NULL,"
-                    + "`username` TEXT,"
-                    + "`last_update` INTEGER,"
-                    + "PRIMARY KEY(`userid`))");
-            database.execSQL("INSERT INTO Users_new "
-                    + " SELECT userid, username, null FROM Users");
-            database.execSQL("DROP TABLE Users");
-            database.execSQL("ALTER TABLE Users_new RENAME TO users");
+            database.execSQL("ALTER TABLE users "
+                    + " ADD COLUMN last_update INTEGER");
         }
     };
 

PersistenceMigrationsSample/app/src/sqlite/java/com/example/android/persistence/migrations/UsersDbHelper.java

@@ -35,7 +35,7 @@ public class UsersDbHelper extends SQLiteOpenHelper {
 
     private static final String SQL_CREATE_ENTRIES =
             "CREATE TABLE " + TABLE_NAME + " (" +
-                    COLUMN_NAME_ENTRY_ID + " INTEGER  PRIMARY KEY," +
+                    COLUMN_NAME_ENTRY_ID + " INTEGER  PRIMARY KEY NOT NULL," +
                     COLUMN_NAME_USERNAME + " TEXT )";
 
     public UsersDbHelper(Context context) {

versions.gradle

@@ -1,3 +1,7 @@
+/**
+* Shared file between builds so that they can all use the same dependencies and
+* maven repositories.
+**/
 ext.deps = [:]
 def versions = [:]
 versions.arch = hasProperty("ARCH_VERSION") ? getProperty("ARCH_VERSION") : "1.0.0-beta2"