No sql databases blrdroid devfest 2016
- 1. NoSQL databases Sometimes being unstructured helps Amrit Sanjeev Organizer @ Blrdroid
- 2. Who am I ?
- 3. Agenda ● Type of databases available in Android ● When to use them ● How they help ? ● Some feature of popular db products
- 4. Data trends - Amount of data stored is increasing - Data is more unstructured - Efficiency and performance are critical - Relations are more complex
- 6. RDBMS vs NoSQL - Structured data - Transform data policy - Atomic transactions - Data model != Entity model - Scale up - Semi or unstructured data - Update schema policy - Eventual consistency - Data model ~= Entity model - Scale out
- 8. Real time database - NoSQL, JSON database - Maps each piece of data to a URL - Offline support - Supports iOS , Android and Web - Pushes updates in milliseconds when things change
- 10. Listening to data changes ● Attach an asynchronous listener to a Firebase reference. ● The listener will be triggered ○ once for the initial state of the data ○ again anytime the data changes Firebase ref = new Firebase("https://docs-examples.firebaseio.com/web/saving-data/fireblog/posts"); ref.addValueEventListener(new ValueEventListener() { @Override public void onDataChange(DataSnapshot snapshot) { System.out.println(snapshot.getValue()); } @Override public void onCancelled(FirebaseError firebaseError) { System.out.println("The read failed: " + firebaseError.getMessage()); } });
- 11. Reading data once ● Callback will be called only once ● removed after the first trigger Firebase ref = new Firebase("https://docs-examples.firebaseio.com/web/saving-data/fireblog/posts"); ref.addListenerForSingleValueEvent(new ValueEventListener() { @Override public void onDataChange(DataSnapshot snapshot) { // do some stuff once } @Override public void onCancelled(FirebaseError firebaseError) { } });
- 12. Querying data ● Selectively retrieve data based on various factors. ● Start by specifying how you want your data to be ordered ○ orderByChild() ○ orderByKey() ○ orderByValue() ○ orderByPriority() ● combine these other methods to conduct complex queries ○ limitToFirst() ○ limitToLast() ○ startAt() ○ endAt() ○ equalTo()
- 14. What is Realm ? - Zero copy object store database - Easy setup - Optimized for read , not writes - Cross platform - Simple Querying interface
- 15. Defining objects in realm public class Person extends RealmObject { @PrimaryKey private long id; private String name; private RealmList<Dog> dogs; // Declare one-to-many relationships // ... Generated getters and setters ... } @RealmClass public class Person implements RealmModel { @PrimaryKey private long id; private String name; private RealmList<Dog> dogs; // Declare one-to-many relationships // ... Generated getters and setters ... }
- 16. Relationships public class Person extends RealmObject { private String firstName; private String lastName; private Dog dog; // ... Generated getters and setters ... } public class Person extends RealmObject { private String firstName; private String lastName; private RealmList<Dog> dogs; // ... Generated getters and setters ... } public class Person extends RealmObject { private String firstName; private String lastName; private RealmList<Person> friends; // .. getters/setters }
- 17. Saving objects in realm // Use them like regular java objects Dog dog = new Dog(); dog.setName("Rex"); dog.setAge("1"); // Get a Realm instance Realm realm = Realm.getDefaultInstance(); // Persist your data easily realm.beginTransaction(); realm.copyToRealm(dog); realm.commitTransaction(); // Get a Realm instance Realm realm = Realm.getDefaultInstance(); // Create and persist your data easily realm.beginTransaction(); Dog dog = realm.createObject(Dog.class); dog.setName("Rex"); dog.setAge("1"); realm.commitTransaction();
- 18. Transactions try { realm.beginTransaction(); Dog dog = realm.where(Dog.class). equalTo("name", "Fido").findFirst(); dog.setAge(15); realm.commitTransaction(); } catch (Exception ex) { // rollback realm.cancelTransaction(); } realm.executeTransaction( new Realm.Transaction() { @Override public void execute(Realm realm) { Dog dog= realm.where(Dog.class). equalTo("name", "Fido").findFirst(); dog.setAge(15); } })
- 19. Async Transactions // Use them like regular java objects realm.executeTransactionAsync(new Realm.Transaction() { @Override public void execute(Realm bgRealm) { User user = bgRealm.createObject(User.class); user.setName("John"); } }, new Realm.Transaction.OnSuccess() { @Override public void onSuccess() { // Transaction was a success. } }, new Realm.Transaction.OnError() { @Override public void onError(Throwable error) { // Transaction failed and was automatically canceled. } }); RealmAsyncTask transaction = realm.executeTransactionAsync( new Realm.Transaction() { @Override public void execute(Realm bgRealm) { User user = bgRealm.createObject(User.class); user.setName("John"); user.setEmail("john@corporation.com"); } }, null);
- 20. Querying data // Build the query looking at all users: RealmQuery<User> query = realm.where(User.class); // Add query conditions: query.equalTo("name", "John"); query.or().equalTo("name", "Peter"); // Execute the query: RealmResults<User> result1 = query.findAll(); // Or alternatively do the same all at once (the "Fluent interface"): RealmResults<User> result2 = realm.where(User.class) .equalTo("name", "John") .or() .equalTo("name", "Peter") .findAll();
- 21. Query data supports - Conditions like lessThan, greaterThan, contains, beginsWith etc - Modifiers for ignoring Cases - Logical Operations OR AND - Sorting Ascending, Descending - Chaining Queries - Aggregations like SUM, MIN, MAX, AVG - Synchronous, Asynchronous operations
- 22. Linked queries public class Person extends RealmObject { private String id; private String name; private RealmList<Dog> dogs; // getters and setters } public class Dog extends RealmObject { private String id; private String name; private String color; // getters and setters }
- 23. Linked queries RealmResults<Person> r1 = realm.where(Person.class) .equalTo("dogs.name", "Fluffy") .findAll(); RealmResults<Person> r2 = r1.where() .equalTo("dogs.color", "Brown") .findAll();
- 24. Auto updating objects Dog d1 = realm.where(Dog.class).equals("id", 123).findFirst(); // register a listener to get notified when the object is updated. d1.registerChangeListener(new RealmChangeListener() { @Override public void onChange() { // called once the query complete and on every update // do something now that the obj is updated } }); // assume code below is in some other thread // Retrieve the same dog as above Dog d2 = realm.where(Dog.class).equals("id", 123).first(); realm.beginTransaction(); d2.setAge(12); realm.commitTransaction(); // d1's change listener gets called after the commit.*
- 25. Migration // Example migration adding a new class RealmMigration MyMigration = new RealmMigration() { @Override public void migrate(DynamicRealm realm, long oldVersion, long newVersion) { // DynamicRealm exposes an editable schema RealmSchema schema = realm.getSchema(); if (oldVersion == 0) { schema.create("Person") .addField("id", long.class, FieldAttribute.PRIMARY_KEY) .addField("name", String.class) .addField("age", int.class); oldVersion++; } } } // in your init RealmConfiguration config = new RealmConfiguration.Builder(context).schemaVersion(1) .migration(new MyMigration()) ;
- 26. More features ● Direct support for Json to Object store ● Notification for database change like CP ● Encryption support in built ● Adapters for binding data with views (Android) ● Cross Platform, same data can work across ios and android ● Robust 3rd parties addons
- 27. Limitations ● Managing memory is tricky ● Not Entirely NOSQL, need migration on schema Changes ● No support for auto incrementing primary keys ● Mutable, thread-confined objects. ● Slower write ● Increase method count and size of apk
- 28. Latest update ● Server side tech ○ Real time sync ○ Conflict resolution ○ Reactive event handling ○ Authentication ○ Access control ● Good to building offline experiences ● Not a managed service yet