cypher-stream

cypher-stream

Neo4j cypher queries as node object streams.

Installation

npm install cypher-stream

Basic usage

var cypher = require('cypher-stream')('bolt://localhost', 'username', 'password');

cypher('match (user:User) return user')
  .on('data', function (result){
    console.log(result.user.first_name);
  })
  .on('end', function() {
    console.log('all done');
  })
;

Handling errors

var cypher = require('cypher-stream')('bolt://localhost', 'username', 'password');
var should = require('should');
it('handles errors', function (done) {
  var errored = false;
    cypher('invalid query')
    .on('error', error => {
      errored = true;
      should.equal(
        error.code,
        'Neo.ClientError.Statement.SyntaxError'
      );
      should.equal(
        error.message,
        'Invalid input \'i\': expected <init> (line 1, column 1 (offset: 0))\n"invalid query"\n ^'
      );
    })
    .on('end', () => {
      should.equal(true, errored);
      done();
    })
    .resume()
    ;
});

Transactions

Transactions are duplex streams that allow you to write query statements and read the results.

Transactions have three methods: write, commit, and rollback, which add queries and commit or rollback the queue respectively.

Creating a transaction

var transaction = cypher.transaction(options)

Adding queries to a transaction

transaction.write(query_statement);

A query_statement can be a string or a query statement object. A query statement object consists of a statement property and an optional parameters property. Additionally, you can pass an array of either.

The following are all valid options:

var transaction = cypher.transaction();

transaction.write('match (n:User) return n');

transaction.write({ statement: 'match (n:User) return n' });

transaction.write({
  statement  : 'match (n:User) where n.first_name = {first_name} return n',
  parameters : { first_name: "Bob" }
});

transaction.write([
  {
    statement  : 'match (n:User) where n.first_name = {first_name} return n',
    parameters : { first_name: "Bob" }
  },
  'match (n:User) where n.first_name = {first_name} return n'
]);

Committing or rolling back

transaction.commit();
transaction.rollback();

Alternatively, a query statement may contain a commit or rollback property.

transaction.write({ statement: 'match (n:User) return n', commit: true });

transaction.write({
  statement  : 'match (n:User) where n.first_name = {first_name} return n',
  parameters : { first_name: "Bob" },
  commit     : true
});

Stream per statement

To get a stream per statement, just pass a callback function with the statement object. This works for regular cypher calls and transactions.

var results = 0;
var calls   = 0;
var ended   = 0;
var query   = 'match (n:Test) return n limit 2';

function callback(stream) {
  stream
    .on('data', function (result) {
      result.should.eql({ n: { test: true } });
      results++;
    })
    .on('end', function () {
      ended++;
    })
  ;
  calls++;
}

var statement = { statement: query, callback: callback };

cypher([ statement, statement ])
.on('end', function () {
  calls.should.equal(2);
  ended.should.equal(2);
  results.should.equal(4);
  done();
})
.resume();

var results = 0;
var calls   = 0;
var ended   = 0;
var query   = 'match (n:Test) return n limit 2';

function callback(stream) {
  stream
    .on('data', function (result) {
      result.should.eql({ n: { test: true } });
      results++;
    })
    .on('end', function () {
      ended++;
    })
  ;
  calls++;
}

var statement = { statement: query, callback: callback };
var transaction = cypher.transaction();

transaction.write(statement);

transaction.write(statement);

transaction.commit();

transaction.resume();

transaction.on('end', function() {
  calls.should.equal(2);
  ended.should.equal(2);
  results.should.equal(4);
  done();
});

Unsafe Integers

Unsafe integers* are returned as strings. If your system deals with particularly large or small numbers, this will require special handling.

See "A note on numbers and the Integer type" on the neo4j-javascript-driver README for more information.

* Unsafe integers are any integers greater than Number.MAX_SAFE_INTEGER or less than Number.MIN_SAFE_INTEGER.