What about multithreading in Android SQLite?

Question

In my app I\'ve got to implement some UI and Sync service. It runs in the background and updates data. Sync service is not very simple, it uses multithreading.

So, here

Answer 1

SQLite implements a exclusive write lock, shared read lock model. This means that you can have concurrent readers active in the database at the same time or a single writer, you can't have both. If you use the WAL logging feature you can have a single writer and multiple readers active in the database at the same time, but you still can't have more than one writer. There is excellent documentation on SQLite concurrency here and here.

You might want to consider taking a look at Berkeley DB. Berkeley DB offers a SQL API that is completely compatible with SQLite. If fact, what we've done is to add the SQLite parser, planner and executor on top of the Berkeley DB storage layer. What this provides to the SQLite application developer is a SQLite-compatible library that has additional scalability, concurrency and reliability (HA), as well as other features. Berkeley DB supports multiple readers and writes concurrently accessing the database. There are two excellent white papers written by Mike Owens, author of "The Definitive Guide to SQLite" that compare Berkeley DB and SQLite (Performance comparison, Behavioral Differences).

Disclaimer: I'm one of the product managers for Berkeley DB, so I'm a little biased. But requests like yours (need more concurrency, scalability, reliability from SQLite) is exactly why we decided to provide a combined library that gives you the best of both worlds.