Graphology Neo4j

Some graphology helpers for Neo4j

Usage

This library doesn’t include the Neo4j driver library as well as the Graphology one. They are peer dependencies, so you need to install them by yourself.

npm install neo4j-driver graphology graphology-neo4j

Translate a cypher query to a graph

You can create a graph directly from a cypher query. The method cypherToGraph will parse the whole result to find Neo4j nodes and relationships for building the graph.

This is the definition of this method :

/**
 * Create a graphology graph based on the result of a cypher query.
 *
 * @param neo4j Object with the neo4j's driver and optionally the database name
 * @param cypher Query to executed for the graph creation
 * @param params Query's parameters
 * @param opts Allow you to defined the graphology attribut mapping for neo4j's ids (default @id), node's labels (default @labels) & relationship's type (default @type).
 * @returns A graphology instance
 */
export function cypherToGraph(
  neo4j: { driver: Driver; database?: string },
  cypher: string,
  params: { [param: string]: unknown } = {},
  opts: CypherToGraphOpts = { id: "@id", labels: "@labels", type: "@type" },
): Promise<Graph>;

Example:

import * as neo4j from "neo4j-driver";
import Graph from "graphology";
import { cypherToGraph } from "graphology-neo4j";

const driver: neo4j.Driver = neo4j.driver("bolt://localhost", neo4j.auth.basic("neo4j", "admin"));
const graph: Graph = await cypherToGraph({ driver }, "MATCH (n)-[r]->(m) RETURN n,r,m");

Create a graph from a Cypher projection

You can create a graph from a cypher projection as defined here, with the help of the method cypherProjectionToGraph .

This is the definition of this method :

/**
 * Create a graphology graph based on the cypher projection queries.
 *
 * @param neo4j Object with the neo4j's driver and optionally the database name
 * @param cypherNodes The query to executed to get nodes. The query must return an `id` field and other fiels with be added as node's property
 * @param cypherRelationships The query to executed to get edges. The query must returns a field `source` and `target`,
 * @param params Query parameters that will be passed to both queries
 * @param opts Allow you to defined the graphology attribut mapping for neo4j's ids (default @id), node's labels (default @labels) & relationship's type (default @type).
 * @returns A graphology instance
 */
export async function cypherProjectionToGraph(
  neo4j: { driver: Driver; database?: string },
  cypherNodes: string,
  cypherRelationships: string,
  params: { [param: string]: unknown } = {},
  opts: CypherToGraphOpts = { id: "@id", labels: "@labels", type: "@type" },
): Promise<Graph>

Example:

import * as neo4j from "neo4j-driver";
import Graph from "graphology";
import { cypherProjectionToGraph } from "graphology-neo4j";

const driver: neo4j.Driver = neo4j.driver("bolt://localhost", neo4j.auth.basic("neo4j", "admin"));
const graph = await cypherProjectionToGraph(
  { driver },
  "MATCH (p:Person) RETURN id(p) AS id, labels(p) AS labels, p.name AS name",
  "MATCH (p1:Person)-[:ACTED_IN]->(:Movie)<-[:ACTED_IN]-(p2:Person) WHERE id(p1) < id(p2) RETURN id(p1) AS source, id(p2) AS target, count(*) AS weight, 'COLLEAGUE' AS type",
  {},
  { id: "_id", labels: "_labels", type: "_type" },
);

Export a graphology graph as a Cypher script

You can export a graph as cypher script, with the help of the method exportToCypher.

Example : const cypherScript = exportToCypher(graph)

It generates a cypher script with CREATE instructions.

The graphology Graph

The graphology created graph is a multi directed graph, where self-loop are allowed (it’s like in Neo4j). But in Graphology the notion of label for nodes and type for relationships don’t exist. That’s why there is the CypherToGraphOpts object where you can define on which property those notions will be saved.

• Graphology and Neo4j id are the same, but they are also stored on nodes and edges in the property @id.

• Neo4j node’s labels are stored in the property @labels

• Neo4j edge’s type is stored in the property @type

Development

To run the tests you need to have a local Neo4j server with Movie database and the password set to admin