p2b2-connector-neo4j

Neo4j Connector

1. Setup of Neo4j database:

Install Neo4J (documentation)

• make sure you have Java 8

wget -O - https://debian.neo4j.org/neotechnology.gpg.key | sudo apt-key add -
echo 'deb https://debian.neo4j.org/repo stable/' | sudo tee /etc/apt/sources.list.d/neo4j.list
sudo apt-get update
sudo apt-get install neo4j

• make sure the nofile limit is high enough:

root soft nofile 40000
root hard nofile 40000

2. First steps with Neo4j

Start the database service

sudo service neo4j start

• go to localhost:7474 (initial password is "neo4j")
• you will be asked to change the password. Change the password to "p2b2"

Cypher Query Language

Cypher is Neo4j’s open graph query language. Cypher’s syntax provides a familiar way to match patterns of nodes and relationships in the graph.

• Use the input field in the web administration tool to do the following exercises:
• Create a node:

CREATE (:Account { address: '0x482e3a38', value: 56})
CREATE (:Contract { address: '0x4326e3a38', value: 56})

• Create a constraint on the Account lable (this also creates an index on the Account address)

CREATE CONSTRAINT ON (account:Account) ASSERT account.address IS UNIQUE;
CREATE CONSTRAINT ON (contract:Contract) ASSERT contract.address IS UNIQUE;

• If we would not have an index from the unique constraint above, we could create it this way to ensure their quick lookup when creating relationships in the next step.

CREATE INDEX ON :Account(address);
CREATE INDEX ON :Contract(address);

• Create an edge:

MATCH (a:Account {address:'0x482e3a38'}), (c:Contract {address:'0x4326e3a38'})
CREATE (a)-[:Transaction { value: 2 }]->(c)

• Create an index on the Transactions' ID

TODO