QueryCursor


Query.prototype.Symbol.asyncIterator()

Returns an asyncIterator for use with for/await/of loops. You do not need to call this function explicitly, the JavaScript runtime will call it for you.

Example

// Works without using `cursor()`
for await (const doc of Model.find([{ $sort: { name: 1 } }])) {
  console.log(doc.name);
}

// Can also use `cursor()`
for await (const doc of Model.find([{ $sort: { name: 1 } }]).cursor()) {
  console.log(doc.name);
}

Node.js 10.x supports async iterators natively without any flags. You can enable async iterators in Node.js 8.x using the --harmony_async_iteration flag.

Note: This function is not if Symbol.asyncIterator is undefined. If Symbol.asyncIterator is undefined, that means your Node.js version does not support async iterators.


QueryCursor()

Parameters
  • query «Query»
  • options «Object» query options passed to .find()

Inherits:
  • «Readable»

A QueryCursor is a concurrency primitive for processing query results one document at a time. A QueryCursor fulfills the Node.js streams3 API, in addition to several other mechanisms for loading documents from MongoDB one at a time.

QueryCursors execute the model's pre find hooks, but not the model's post find hooks.

Unless you're an advanced user, do not instantiate this class directly. Use Query#cursor() instead.


QueryCursor.prototype.addCursorFlag()

Parameters
  • flag «String»
  • value «Boolean»
Returns:
  • «AggregationCursor» this

Adds a cursor flag. Useful for setting the noCursorTimeout and tailable flags.


QueryCursor.prototype.close()

Parameters
  • callback «Function»
Returns:
  • «Promise»

Marks this cursor as closed. Will stop streaming and subsequent calls to next() will error.


QueryCursor.prototype.eachAsync()

Parameters
  • fn «Function»
  • [options] «Object»
    • [options.parallel] «Number» the number of promises to execute in parallel. Defaults to 1.

  • [callback] «Function» executed when all docs have been processed

Returns:
  • «Promise»

Execute fn for every document in the cursor. If fn returns a promise, will wait for the promise to resolve before iterating on to the next one. Returns a promise that resolves when done.

Example

// Iterate over documents asynchronously
Thing.
  find({ name: /^hello/ }).
  cursor().
  eachAsync(async function (doc, i) {
    doc.foo = doc.bar + i;
    await doc.save();
  })

QueryCursor.prototype.map()

Parameters
  • fn «Function»
Returns:
  • «QueryCursor»

Registers a transform function which subsequently maps documents retrieved via the streams interface or .next()

Example

// Map documents returned by `data` events
Thing.
  find({ name: /^hello/ }).
  cursor().
  map(function (doc) {
   doc.foo = "bar";
   return doc;
  })
  on('data', function(doc) { console.log(doc.foo); });

// Or map documents returned by `.next()`
const cursor = Thing.find({ name: /^hello/ }).
  cursor().
  map(function (doc) {
    doc.foo = "bar";
    return doc;
  });
cursor.next(function(error, doc) {
  console.log(doc.foo);
});

QueryCursor.prototype.next()

Parameters
  • callback «Function»
Returns:
  • «Promise»

Get the next document from this cursor. Will return null when there are no documents left.


function Object() { [native code] }.prototype.options

Type:
  • «property»

The options passed in to the QueryCursor constructor.