Graph support

Client includes the executeGraph() method to execute graph queries:

const client = new cassandra.Client({
  contactPoints: ['host1', 'host2'],
  graphOptions: { name: 'demo' }
});

// executeGraph() method returns a Promise
client.executeGraph('g.V()')
  .then(function (result) {
    const vertex = result.first();
    console.log(vertex.label);
  });

Alternatively, you can use the callback-based execution:

client.executeGraph('g.V()', function (err, result) {
  assert.ifError(err);
  const vertex = result.first();
  // ...
});

Graph Options

You can set default graph options when initializing Client which will be used for all graph statements. For example, to avoid providing a graphName option in each executeGraph() call:

const cassandra = require('cassandra-driver');
const client = new cassandra.Client({
  contactPoints: ['host1', 'host2'],
  graphOptions: { name: 'demo' }
});

These options may be overridden by specifying the execution profile when calling executeGraph():

// Use a different graph name than the one provided when creating the client instance
const result = await client.executeGraph(query, params, { executionProfile: 'graph-oltp' });
const vertex = result.first();
console.log(vertex.label);

You can check out more info on Execution Profiles.

Handling Results

Graph queries return a GraphResultSet, which is an iterable of rows. The format of the data returned is dependent on the data requested. For example, the payload representing edges will be different than those that represent vertices using the ‘modern’ graph:

// Creating the 'modern' graph
const query =
  'Vertex marko = graph.addVertex(label, "person", "name", "marko", "age", 29);\n' +
  'Vertex vadas = graph.addVertex(label, "person", "name", "vadas", "age", 27);\n' +
  'Vertex lop = graph.addVertex(label, "software", "name", "lop", "lang", "java");\n' +
  'Vertex josh = graph.addVertex(label, "person", "name", "josh", "age", 32);\n' +
  'Vertex ripple = graph.addVertex(label, "software", "name", "ripple", "lang", "java");\n' +
  'Vertex peter = graph.addVertex(label, "person", "name", "peter", "age", 35);\n' +
  'marko.addEdge("knows", vadas, "weight", 0.5f);\n' +
  'marko.addEdge("knows", josh, "weight", 1.0f);\n' +
  'marko.addEdge("created", lop, "weight", 0.4f);\n' +
  'josh.addEdge("created", ripple, "weight", 1.0f);\n' +
  'josh.addEdge("created", lop, "weight", 0.4f);\n' +
  'peter.addEdge("created", lop, "weight", 0.2f);';

await client.executeGraph(query);

// Handling Edges
const result = await client.executeGraph('g.E()');
result.forEach(function (edge) {
  console.log(edge.id); // [an internal id representing the edge]
  console.log(edge.type); // edge
  console.log(edge.label); // created
  console.log(edge.properties.weight); // 0.4
  console.log(edge.outVLabel); // person
  console.log(edge.outV); // [an id representing the outgoing vertex]
  console.log(edge.inVLabel); // software
  console.log(edge.inV); // [an id representing the incoming vertex]
});

// Using ES6 for...of
const result = await client.executeGraph('g.E()');
for (let edge of result) {
  console.log(edge.label); // created
  // ...
}

// Handling Vertices
const result = await client.executeGraph('g.V().hasLabel("person")');
result.forEach(function(vertex) {
  console.log(vertex.id); // [an internal id representing the vertex]
  console.log(vertex.type); // vertex
  console.log(vertex.label); // person
  console.log(vertex.properties.name[0].value); // marko
  console.log(vertex.properties.age[0].value); // 29
});

Parameters

Unlike CQL queries which support both positional and named parameters, graph queries only support named parameters. As a result of this, parameters must be passed in as an object:

const query = 'g.addV(label, vertexLabel, "name", username)';
const result = await client.executeGraph(query, { vertexLabel: 'person', username: 'marko' });
const vertex = result.first();

Parameters are encoded in json, thus will ultimately use their json representation (toJSON if present, otherwise object representation).

You can use results from previous queries as parameters to subsequent queries. For example, if you want to use the id of a vertex returned in a previous query for making a subsequent query:

let result = await client.executeGraph('g.V().hasLabel("person").has("name", "marko")');
const vertex = result.first();
result = await client.executeGraph('g.V(vertexId).out("knows").values("name")', {vertexId: vertex.id });
const names = result.toArray();
console.log(names); // [ 'vadas', 'josh' ]

Prepared statements

Prepared graph statements are not supported by DSE Graph yet (they will be added in the near future).