class Client

Executes batch of queries on an available connection to a host.

It returns a Promise when a callback is not provided.

Parameters:

Name	Type	Description
queries	Array<string> or Array<{query, params}>	The queries to execute as an Array of strings or as an array of object containing the query and params
options optional	QueryOptions	The query options.
callback optional	ResultCallback	Executes callback(err, result) when the batch was executed

Attempts to connect to one of the contactPoints and discovers the rest the nodes of the cluster.

When the Client is already connected, it resolves immediately.

It returns a Promise when a callback is not provided.

Examples:

Usage example

await client.connect();

Parameters:

Name	Type	Description
callback optional	function	The optional callback that is invoked when the pool is connected or it failed to connect.

Executes the query and calls rowCallback for each row as soon as they are received. Calls the final callback after all rows have been sent, or when there is an error.

The query can be prepared (recommended) or not depending on the prepare flag.

Examples:

Using per-row callback and arrow functions

client.eachRow(query, params, { prepare: true }, (n, row) => console.log(n, row), err => console.error(err));

Overloads

client.eachRow(query, rowCallback);
client.eachRow(query, params, rowCallback);
client.eachRow(query, params, options, rowCallback);
client.eachRow(query, params, rowCallback, callback);
client.eachRow(query, params, options, rowCallback, callback);

Parameters:

Name	Type	Description
query	String	The query to execute
params optional	Array or Object	Array of parameter values or an associative array (object) containing parameter names as keys and its value.
options optional	QueryOptions	The query options.
rowCallback	function	Executes rowCallback(n, row) per each row received, where n is the row index and row is the current Row.
callback optional	function	Executes callback(err, result) after all rows have been received. When dealing with paged results, ResultSet#nextPage() method can be used to retrieve the following page. In that case, rowCallback() will be again called for each row and the final callback will be invoked when all rows in the following page has been retrieved.

Executes a query on an available connection.

The query can be prepared (recommended) or not depending on the prepare flag.

Some execution failures can be handled transparently by the driver, according to the RetryPolicy or the SpeculativeExecutionPolicy used.

It returns a Promise when a callback is not provided.

Examples:

Promise-based API, using async/await

const query = 'SELECT name, email FROM users WHERE id = ?';
const result = await client.execute(query, [ id ], { prepare: true });
const row = result.first();
console.log('%s: %s', row['name'], row['email']);

Callback-based API

const query = 'SELECT name, email FROM users WHERE id = ?';
client.execute(query, [ id ], { prepare: true }, function (err, result) {
  assert.ifError(err);
  const row = result.first();
  console.log('%s: %s', row['name'], row['email']);
});

Parameters:

Name	Type	Description
query	String	The query to execute.
params optional	Array or Object	Array of parameter values or an associative array (object) containing parameter names as keys and its value.
options optional	QueryOptions	The query options for the execution.
callback optional	ResultCallback	Executes callback(err, result) when execution completed. When not defined, the method will return a promise.

Executes a graph query.

It returns a Promise when a callback is not provided.

Examples:

Promise-based API, using async/await

const result = await client.executeGraph('g.V()');
// Get the first item (vertex, edge, scalar value, ...)
const vertex = result.first();
console.log(vertex.label);

Callback-based API

client.executeGraph('g.V()', (err, result) => {
  const vertex = result.first();
  console.log(vertex.label);
});

Iterating through the results

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

Using result.forEach()

const result = await client.executeGraph('g.V().hasLabel("person")');
result.forEach(function(vertex) {
  console.log(vertex.type); // vertex
  console.log(vertex.label); // person
});

Parameters:

Name	Type	Description
query	String	The gremlin query.
parameters optional	Object or null	An associative array containing the key and values of the parameters.
options optional	GraphQueryOptions or null	The graph query options.
callback optional	function	Function to execute when the response is retrieved, taking two arguments: err and result. When not defined, the method will return a promise.

Gets the host that are replicas of a given token.

Parameters:

Name	Type	Description
keyspace	String
token	Buffer

Returns:

Type	Description
Array<Host>

Gets a snapshot containing information on the connections pools held by this Client at the current time.

The information provided in the returned object only represents the state at the moment this method was called and it’s not maintained in sync with the driver metadata.

Returns:

Type	Description
ClientState	A ClientState instance.

Closes all connections to all hosts.

It returns a Promise when a callback is not provided.

Parameters:

Name	Type	Description
callback optional	function	Optional callback to be invoked when finished closing all connections.

Executes the query and pushes the rows to the result stream as soon as they received.

The stream is a ReadableStream object that emits rows. It can be piped downstream and provides automatic pause/resume logic (it buffers when not read).

The query can be prepared (recommended) or not depending on QueryOptions.prepare flag. Retries on multiple hosts if needed.

Parameters:

Name	Type	Description
query	String	The query to prepare and execute.
params optional	Array or Object	Array of parameter values or an associative array (object) containing parameter names as keys and its value
options optional	QueryOptions	The query options.
callback optional	function	executes callback(err) after all rows have been received or if there is an error

Returns:

Type	Description
ResultStream