Describe a scenario where Room's built-in conflict resolution strategies might not suffice and require custom conflict handling. Explain how you would implement this custom solution.
Android interview question for Advanced practice.
Answer
A common scenario where Room's default conflict resolution is insufficient is when multiple users simultaneously modify the same data. For example, consider a collaborative note-taking app. Two users might try to update the same note at the same time. Room's default ABORT strategy would prevent one of the updates from succeeding. To handle this, we would implement a custom conflict strategy using @OnConflictStrategy(REPLACE) along with a mechanism to merge conflicting data. This might involve checking timestamps, comparing data versions, or implementing a more sophisticated merge algorithm. The custom logic would be executed within the DAO's insert or update methods. The algorithm could check the last updated timestamp and use that to resolve the conflict.
Explanation
Room's conflict resolution strategies are based on the ABORT strategy by default. This means that if a conflict occurs, the second operation will fail.