ObjectBox

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ObjectBox is an object-oriented DBMS library built for IoT and mobile devices. ObjectBox supports an extensive list of programming languages, including Java, C/C++, Go, Swift, Kotlin, and Python. Therefore, ObjectBox runs on multiple platforms: Linux, Windows, Mac/iOS, and Android.

ObjectBox stores the objects directly, instead of storing data in relational DBs and accessing them through an ORM layer. It has full ACID compatibility, provides transaction semantics, and uses MVCC for concurrency control.

ObjectBox was created by the same team that created greenDAO, an Android ORM library, so it also provides briding APIs for greenDAO users.

History

ObjectBox is presented by greenrobot. In 2011, They first created greenDAO, an Android ORM library that uses SQLite as backend. The team then decided to abandon the SQLite + ORM architecture for better performance and to build a NoSQL object-oriented DBMS from scratch, which is ObjectBox. ObjectBox is first in public beta release on 2017/1/24.

Concurrency Control

Multi-version Concurrency Control (MVCC)

Data Model

Object-Oriented

ObjectBox is object-oriented. Objects are stored directly without another layer of relational tables.

Joins in ObjectBox is implemented using relations stored in each object. Each object stores reference to the other object(s) in the relation, which is similar to index nested loop join.

Stored Procedures

Not Supported

The DB itself don't have stored procedures, but it can be implemented using functions in the corresponding programming language when run as an embedded database.

Storage Architecture

Hybrid

Low-level mmap approach taking care of OS in-memory caches and ACID compliant disk storage

Indexes

B+Tree

B+ tree based with 3 different options: value, 32 bit hash, 64 bit hash (hashes for string values only)

Foreign Keys

Supported

Foreign keys are maintained by relations in each entity. There are 2 kinds of relations: ToOne and ToMany. By combining the type of the relation and the type of the reverse relation, the user can define one-to-one, one-to-many, and many-to-many relations.

Views

Not Supported

Query Interface

Custom API

ObjectBox provides builder APIs for creating queries. Created queries are reusable by setting different parameters.

System Architecture

Embedded

The DB runs on IoT and mobile devices and does not share disk or memory with other devices. However, the ObjectBox supports automatic synchronization of data with the backend server. When the server is unavailable (i.e. network failure), the synchronization will stop, and it is restored seamlessly when the server is available again.