在我的应用程序中升级SQLite数据库架构

Question

If I have 3 different database schemas, is it possible for a user to upgrade to version 2? In other words, do I need to check for every possible combination of oldVersion and newVersion in the onUpgrade() method of my SQLiteOpenHelper subclass?

Clarification:

After I release an update with a 3rd database schema is it possible that onUpgrade() will be called with a newVersion of 2 (where the original database schema is 1 and the newest one is 3)?

Answer 1

It is possible for them to skip a version, but this doesn't mean you have to check for every possible combination. What I usually do is put the upgrades in their unique methods and call those methods from a switch :

private void updateTo1(){
   //Code to update schema to version 1.
}

private void updateTo2(){
   //Code to update schema to version 2.
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
   switch(oldVersion){
      case 0:
         updateTo1();
      case 1:
         updateTo2();
   }
}

This will ensure that even if they upgrade from version 0 straight to version 2, the schema will first go through version 1 making sure that it's compatible with and ready for the version 2 update.