List of Figures

Chapter 1. A case for a Neo4j database

Figure 1.1. Users and their friends represented as a graph data structure

Figure 1.2. SQL diagram of tables representing user and friend data

Figure 1.3. Traversing the social network graph data

Chapter 2. Data modeling in Neo4j

Figure 2.1. Users and groups in an RDBMS with a join table

Figure 2.2. A person belongs to a group.

Figure 2.3. Three people in two groups

Figure 2.4. The entities in an access control system

Figure 2.5. Relationships between entities in the access control system

Figure 2.6. The access control model extended to support subgroups

Figure 2.7. A User with some properties

Figure 2.8. The user with some nodes converted to properties

Figure 2.9. Two users with different relationships to the same address

Figure 2.10. Two users with differently qualified relationships to the same address

Figure 2.11. Reifying the relationship between a User and an Address in order to introduce other participants

Figure 2.12. A User with additional properties stored in a related UserEx node

Figure 2.13. Two underground stations, with the connection between them reified as a single Track Section

Figure 2.14. Two underground stations, with connections on two different lines

Figure 2.15. A simple model showing band members and a recorded album

Figure 2.16. A more complex model showing two different lineups of the same band

Chapter 3. Starting development with Neo4j

Figure 3.1. Users in a social network represented as boxes

Figure 3.2. Simple social network graph with users connected as friends

Figure 3.3. Richer model with a name property assigned to each user

Figure 3.4. Introducing movies to the model

Figure 3.5. Introducing type properties to differentiate between User and Movie elements

Figure 3.6. Complete model of a movie-lover’s social network

Figure 3.7. Graph with only node entities

Figure 3.8. Simple social network graph with users connected as friends

Figure 3.9. Rich property graph representing the social network

Figure 3.10. Graph with nodes representing users and movies

Figure 3.11. Nodes using the type property strategy

Figure 3.12. Complete model of a movie-lovers’ social network

Figure 3.13. Movie nodes grouped using the label MOVIE

Chapter 4. The power of traversals

Figure 4.1. The selected user and the movies he’s seen are marked with a bold border.

Figure 4.2. Nodes and relationships to follow to find movies that John’s friends like

Chapter 5. Indexing the data

Figure 5.1. Index pointing to user nodes as values, using the email property as a key

Figure 5.2. Looking up a user node from the index by using the email property

Figure 5.3. User nodes indexed by the age property, with each key potentially referencing multiple nodes

Figure 5.4. Graph of a social network using intermediate nodes to differentiate between relationships to user and film nodes.

Figure 5.5. Performance of node lookup using index compared to iterating through all nodes

Figure 5.6. Average time for storing user node with and without indexing

Chapter 6. Cypher: Neo4j query language

Figure 6.1. A social network graph to be queried

Figure 6.2. The Neo4j Shell ready to accept commands

Figure 6.3. Cypher is executed in the Neo4j Shell natively, resulting in tabular output.

Figure 6.4. Homepage of the Neo4j Web Admin Console in the browser

Figure 6.5. Executing a Cypher query inside the Web Admin Console

Figure 6.6. Result of the query execution in Neo4j Shell, finding movie recommendations for the user based on the movies their friends have seen

Chapter 7. Transactions

Figure 7.1. Default isolation level

Figure 7.2. Explicit read locks

Chapter 8. Traversals in depth

Figure 8.1. Simple graph with nine nodes and eight relationships

Figure 8.2. Walking the graph using depth-first ordering

Figure 8.3. Breadthfirst traversal of the sample graph

Figure 8.4. A social network of users and movies they like

Figure 8.5. A simple social network graph

Figure 8.6. Bidirectional traversal used to find the path between two nodes

Chapter 9. Spring Data Neo4j

Figure 9.1. Overview of where SDN fits within your broader application

Figure 9.2. Conceptual overview of the movie-lovers’ social network, with referrals

Figure 9.3. Social network model with nodes highlighted

Figure 9.4. A social network model with highlighted relationships that could potentially be modeled as relationship entities

Figure 9.5. A social network model with the relationship references between nodes highlighted

Figure 9.6. Overview of SDN repository classes involved in accessing User node entity

Figure 9.7. Overview of the simple mapping logic

Figure 9.8. Advanced mapping overview

Figure 9.9. Friends-of-friends submodel

Chapter 10. Neo4j: embedded versus server mode

Figure 10.1. Overview of Neo4j usage modes and the main integration options for clients

Figure 10.2. Typical Java-embedded deployment scenario, where the Neo4j libraries are embedded in the Java application

Figure 10.3. Other JVM-based embedded deployment approaches, involving language-specific wrappers and drivers for Neo4j

Figure 10.4. A typical Neo4j server setup with client access via the standard REST API

Figure 10.5. Server-based deployment approach using remote REST client libraries

Figure 10.6. Accessing Neo4j via server plugins and unmanaged extensions

Figure 10.7. Two possible deployment scenarios for the social network application: embedded and server modes

Figure 10.8. Result of turning streaming on/off

Chapter 11. Neo4j in production

Figure 11.1. High-level overview of the Neo4j architecture

Figure 11.2. Neo4j’s use of RAM for caching

Figure 11.3. Recap of where transaction logs fit into the overall Neo4j architecture

Figure 11.4. Programmatic API stack

Figure 11.5. Sample Neo4j HA cluster setup with 1 master and 2 slaves

Figure 11.6. Web Admin Console view of HA setup from machine01’s perspective

Figure 11.7. Web Admin Console view of HA setup from machine02’s perspective

Figure 11.8. Sequence of events when a write request is sent to the master instance

Figure 11.9. Sequence of events when a write request is sent to a slave instance

Figure 11.10. Cache sharding

Figure 11.11. Example backup scenario for a single server setup

Appendix A. Installing Neo4j server

Figure A.1. The Neo4j browser splash page

Figure A.2. The Neo4j browser splash page with expanded sidebar

Figure A.3. The Neo4j browser’s graphical visualization of nodes in the system

Figure A.4. Neo4j Web Admin Console

Appendix B. Setting up and running the sample code

Figure B.1. Default Maven output for chapter 10