2

In my android app, I was using a standard SQLite database with a helper class that had 1 table with 3 columns. In the most recent update I had to add another column of to the table, but some users have reported crashes, which (judging by the stack trace) I think comes from the new version trying to read from a column that does not exist because the data is from the old version. How can I protect the users' data between updates short of a manual backup and restore?

Here is the link to the complete updated database class: https://github.com/cjbrooks12/scripturememory/blob/working/src/com/caseybrooks/scripturememory/databases/VersesDatabase.java

Improve this question

1 Answer 1

Reset to default
6

SQLiteOpenHelper will handle the database versioning, you will just have to provide it with proper database version numbers and overridden callbacks. Looking at your code:

  1. Your DB_VERSION is 1. When you change the database schema between released versions, you should increment this number. The version number is stored in the database file, and if the version provided in code is different from the one stored in file, onUpgrade() or onDowngrade() will be called accordingly. In your case, since the database file already exists, no onCreate() was called and since the version numbers matched, no upgrade was performed.

  2. Your onUpgrade() drops the table and then recreates it. In some cases this might be ok, say, it's just a cached copy of data stored elsewhere, but usually as a user, I don't want an app upgrade to delete my data. Implement onUpgrade() so that it does the necessary schema modifications while preserving data. Some generic strategies for this:

    • If it's just adding some columns ALTER TABLE and put some suitable default values.

    • If it's more complex schema change, rename the old tables to temporary names, create new tables and then migrate data from the temp tables.

    In any case, after onUpgrade() the database schema should be in the same shape it would be if onCreate() was called to create a new database, but with existing data preserved.

Improve this answer
Sign up to request clarification or add additional context in comments.

Comments

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.