avsector / sqlbrite

A lightweight wrapper around SQLiteOpenHelper which introduces reactive stream semantics to SQL operations.

SQLBrite

A lightweight wrapper around SQLiteOpenHelper and ContentResolver which introduces reactive stream semantics to queries.

Usage

Create a SqlBrite instance which is an adapter for the library functionality.

SqlBrite sqlBrite = SqlBrite.create();

Pass a SQLiteOpenHelper instance and a Scheduler to create a BriteDatabase.

BriteDatabase db = sqlBrite.wrapDatabaseHelper(openHelper, Schedulers.io());

A Scheduler is required for a few reasons, but the most important is that query notifications can trigger on the thread of your choice. The query can then be run without blocking the main thread or the thread which caused the trigger.

The BriteDatabase.createQuery method is similar to SQLiteDatabase.rawQuery except it takes an additional parameter of table(s) on which to listen for changes. Subscribe to the returned Observable<Query> which will immediately notify with a Query to run.

Observable<Query> users = db.createQuery("users", "SELECT * FROM users");
users.subscribe(new Action1<Query>() {
  @Override public void call(Query query) {
    Cursor cursor = query.run();
    // TODO parse data...
  }
});

Unlike a traditional rawQuery, updates to the specified table(s) will trigger additional notifications for as long as you remain subscribed to the observable. This means that when you insert, update, or delete data, any subscribed queries will update with the new data instantly.

final AtomicInteger queries = new AtomicInteger();
users.subscribe(new Action1<Query>() {
  @Override public void call(Query query) {
    queries.getAndIncrement();
  }
});
System.out.println("Queries: " + queries.get()); // Prints 1

db.insert("users", createUser("jw", "Jake Wharton"));
db.insert("users", createUser("mattp", "Matt Precious"));
db.insert("users", createUser("strong", "Alec Strong"));

System.out.println("Queries: " + queries.get()); // Prints 4

In the previous example we re-used the BriteDatabase object "db" for inserts. All insert, update, or delete operations must go through this object in order to correctly notify subscribers.

Unsubscribe from the returned Subscription to stop getting updates.

final AtomicInteger queries = new AtomicInteger();
Subscription s = users.subscribe(new Action1<Query>() {
  @Override public void call(Query query) {
    queries.getAndIncrement();
  }
});
System.out.println("Queries: " + queries.get()); // Prints 1

db.insert("users", createUser("jw", "Jake Wharton"));
db.insert("users", createUser("mattp", "Matt Precious"));
s.unsubscribe();

db.insert("users", createUser("strong", "Alec Strong"));

System.out.println("Queries: " + queries.get()); // Prints 3

Use transactions to prevent large changes to the data from spamming your subscribers.

final AtomicInteger queries = new AtomicInteger();
users.subscribe(new Action1<Query>() {
  @Override public void call(Query query) {
    queries.getAndIncrement();
  }
});
System.out.println("Queries: " + queries.get()); // Prints 1

Transaction transaction = db.newTransaction();
try {
  db.insert("users", createUser("jw", "Jake Wharton"));
  db.insert("users", createUser("mattp", "Matt Precious"));
  db.insert("users", createUser("strong", "Alec Strong"));
  transaction.markSuccessful();
} finally {
  transaction.end();
}

System.out.println("Queries: " + queries.get()); // Prints 2

Note: You can also use try-with-resources with a Transaction instance.

Since queries are just regular RxJava Observable objects, operators can also be used to control the frequency of notifications to subscribers.

users.debounce(500, MILLISECONDS).subscribe(new Action1<Query>() {
  @Override public void call(Query query) {
    // TODO...
  }
});

The SqlBrite object can also wrap a ContentResolver for observing a query on another app's content provider.

BriteContentResolver resolver = sqlBrite.wrapContentProvider(contentResolver, Schedulers.io());
Observable<Query> query = resolver.createQuery(/*...*/);

The full power of RxJava's operators are available for combining, filtering, and triggering any number of queries and data changes.

Philosophy

SqlBrite's only responsibility is to be a mechanism for coordinating and composing the notification of updates to tables such that you can update queries as soon as data changes.

This library is not an ORM. It is not a type-safe query mechanism. It won't serialize the same POJOs you use for Gson. It's not going to perform database migrations for you.

Some of these features are offered by SQLDelight which can be used with SQLBrite.

Download

compile 'com.squareup.sqlbrite:sqlbrite:0.7.0'

Snapshots of the development version are available in Sonatype's snapshots repository.

License

Copyright 2015 Square, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.