Graph Databases

Chapter 6. Graph Database Internals

In this chapter we peek under the hood and discuss the implementation of graph databases, showing how they differ from other means of storing and querying complex, semi-structured, densely connected data. Although it is true that no single universal architecture pattern exists, even among graph databases, this chapter describes the most common architecture patterns and components you can expect to find inside a graph database.

We illustrate the discussion in this chapter using the Neo4j graph database, for several reasons. Neo4j is a graph database with native processing capabilities as well as native graph storage (see Chapter 1 for a discussion of native graph processing and storage). In addition to being the most common graph database in use at the time of writing, it has the transparency advantage of being open source, making it easy for the adventuresome reader to go a level deeper and inspect the code. Finally, it is a database the authors know well.

Native Graph Processing

We’ve discussed the property graph model several times throughout this book; by now you should be familiar with its notion of nodes connected by way of named and directed relationships, with both the nodes and relationships serving as containers for properties. Although the model itself is reasonably consistent across graph database implementations, there are numerous ways to encode and represent the graph in the database engine’s main memory. Of the many different engine ...