Java Multi-Model API
(since v 3.0)
OrientDB was born as a Document database. The fact that it has physical links (index-free adjacency) makes it a graph database, but still, the core API was designed as a Document API; the Graph API was added later, as a separate component, based on Apache TinkerPop 2.x standard.
This led to a big discrepancy between the two APIs. See these two examples:
// The Document API version ODatabaseDocument db; ... db.begin(); ODocument doc = db.newInstance("Person"); doc.field("name", "John"); doc.save(); db.commit() db.close();
// The Graph API (Apache TinkerPop 2.6) version Graph graph; ... OrientVertex v = graph.addVertex("class:Person"); v.setProperty("name", "John"); graph.commit(); graph.shutdown();
You can easily see the differences:
- different class hierarchies: ODocument and OrientVertex have only a common parent interface - OIdentifiable - that doesn't even have methods to retrieve and manipulate properties
- different way to instantiate records:
- different manipulation API:
- different object lifecycle: did you notice the
In OrientDB is a MultiModel db, so in v 3.0 we decided it was time to privide a single, unified Multi-Model API.
This means that with
ODatabaseDocument instances you can query documents, but also graphs, without the need for an additional API.
Don't worry, Apache TinkerPop 2.6 - together with the new 3.x - is still there, just as a separate dependency, so if you rely on that you will have no problems migrating
Before we give you a complete overview of the new Multi-Model API, here is a basic example that demonstrates how it works:
ODatabaseDocument db; ... OElement d = db.newInstance("DocClass"); d.setProperty("foo", "Bar"); d.save(); OVertex v1 = db.newVertex("VertexClass"); v1.setProperty("foo", "One"); v1.save(); OVertex v2 = db.newVertex("VertexClass"); v2.setProperty("foo", "Two"); v2.save(); v1.addEdge(v2, "EdgeClass").save(); db.commit();
Multi-Model Data Hierarchy
The picture below shows the interface hierarchy of the Multi-Model API
ORecord: this is a pre-existing interface, common to all the persistent records
Its main goal is to provide an abstraction to obtain low level information (eg. identity) and behavior (eg. save and delete) for persistent entries
OBlob: represents BLOB (binary) records
OElement: represents plain documents (so also vertices and edges). It includes methods to manipulate properties and to check if current element is a vertex or an edge.
Attention: until v 2.2 the Document API relied on ODocument class only. ODocument is still there as the main implementation of
OElement, but please don't use it directly, always use
OVertex: is the basic interface for vertices, it includes methods to manipulate and traverse connected edges and vertices
OEdge: is the basic interface for edges, it includes methods to retrieve info regarding connected vertices
Query Mechanisms and Interfaces
In v.2.2 you needed the orientdb-graphdb module to perform graph queries (eg. queries that use
in V 3.0 we moved all the basic graph operators to the core module, basically you don't need orientdb-graphdb anymore, unless
you need explicit support for Apache TinkerPop API.
V 3.0 also includes a new query interface that explicitly return elements that can be converted to the Multi-Model interface hierarchy.