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521 lines
13 KiB
521 lines
13 KiB
/*!
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* Module dependencies.
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*/
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'use strict';
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const Readable = require('stream').Readable;
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const promiseOrCallback = require('../helpers/promiseOrCallback');
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const eachAsync = require('../helpers/cursor/eachAsync');
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const helpers = require('../queryhelpers');
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const immediate = require('../helpers/immediate');
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const util = require('util');
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const utils = require('../../lib/utils');
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/**
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* A QueryCursor is a concurrency primitive for processing query results
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* one document at a time. A QueryCursor fulfills the Node.js streams3 API,
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* in addition to several other mechanisms for loading documents from MongoDB
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* one at a time.
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*
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* QueryCursors execute the model's pre `find` hooks before loading any documents
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* from MongoDB, and the model's post `find` hooks after loading each document.
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*
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* Unless you're an advanced user, do **not** instantiate this class directly.
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* Use [`Query#cursor()`](/docs/api.html#query_Query-cursor) instead.
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*
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* @param {Query} query
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* @param {Object} options query options passed to `.find()`
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* @inherits Readable
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* @event `cursor`: Emitted when the cursor is created
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* @event `error`: Emitted when an error occurred
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* @event `data`: Emitted when the stream is flowing and the next doc is ready
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* @event `end`: Emitted when the stream is exhausted
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* @api public
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*/
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function QueryCursor(query, options) {
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const streamOpts = { objectMode: true };
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// for node < 12 we will emit 'close' event after 'end'
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if (utils.nodeMajorVersion >= 12) {
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// set autoDestroy=true because on node 12 it's by default false
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// gh-10902 need autoDestroy to destroy correctly and emit 'close' event for node >= 12
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streamOpts.autoDestroy = true;
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}
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Readable.call(this, streamOpts);
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this.cursor = null;
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this.query = query;
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const _this = this;
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const model = query.model;
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this._mongooseOptions = {};
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this._transforms = [];
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this.model = model;
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this.options = options || {};
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model.hooks.execPre('find', query, () => {
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this._transforms = this._transforms.concat(query._transforms.slice());
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if (this.options.transform) {
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this._transforms.push(options.transform);
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}
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// Re: gh-8039, you need to set the `cursor.batchSize` option, top-level
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// `batchSize` option doesn't work.
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if (this.options.batchSize) {
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this.options.cursor = options.cursor || {};
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this.options.cursor.batchSize = options.batchSize;
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// Max out the number of documents we'll populate in parallel at 5000.
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this.options._populateBatchSize = Math.min(this.options.batchSize, 5000);
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}
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model.collection.find(query._conditions, this.options, function(err, cursor) {
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if (_this._error) {
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if (cursor != null) {
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cursor.close(function() {});
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}
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_this.emit('cursor', null);
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_this.listeners('error').length > 0 && _this.emit('error', _this._error);
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return;
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}
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if (err) {
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return _this.emit('error', err);
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}
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_this.cursor = cursor;
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_this.emit('cursor', cursor);
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});
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});
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}
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util.inherits(QueryCursor, Readable);
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/*!
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* Necessary to satisfy the Readable API
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*/
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QueryCursor.prototype._read = function() {
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const _this = this;
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_next(this, function(error, doc) {
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if (error) {
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return _this.emit('error', error);
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}
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if (!doc) {
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_this.push(null);
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_this.cursor.close(function(error) {
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if (error) {
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return _this.emit('error', error);
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}
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// for node >= 12 the autoDestroy will emit the 'close' event
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if (utils.nodeMajorVersion < 12) {
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_this.on('end', () => _this.emit('close'));
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}
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});
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return;
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}
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_this.push(doc);
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});
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};
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/**
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* Registers a transform function which subsequently maps documents retrieved
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* via the streams interface or `.next()`
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*
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* ####Example
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*
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* // Map documents returned by `data` events
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* Thing.
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* find({ name: /^hello/ }).
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* cursor().
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* map(function (doc) {
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* doc.foo = "bar";
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* return doc;
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* })
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* on('data', function(doc) { console.log(doc.foo); });
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*
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* // Or map documents returned by `.next()`
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* const cursor = Thing.find({ name: /^hello/ }).
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* cursor().
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* map(function (doc) {
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* doc.foo = "bar";
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* return doc;
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* });
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* cursor.next(function(error, doc) {
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* console.log(doc.foo);
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* });
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*
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* @param {Function} fn
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* @return {QueryCursor}
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* @api public
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* @method map
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*/
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QueryCursor.prototype.map = function(fn) {
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this._transforms.push(fn);
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return this;
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};
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/*!
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* Marks this cursor as errored
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*/
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QueryCursor.prototype._markError = function(error) {
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this._error = error;
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return this;
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};
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/**
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* Marks this cursor as closed. Will stop streaming and subsequent calls to
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* `next()` will error.
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*
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* @param {Function} callback
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* @return {Promise}
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* @api public
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* @method close
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* @emits close
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* @see MongoDB driver cursor#close http://mongodb.github.io/node-mongodb-native/2.1/api/Cursor.html#close
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*/
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QueryCursor.prototype.close = function(callback) {
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return promiseOrCallback(callback, cb => {
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this.cursor.close(error => {
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if (error) {
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cb(error);
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return this.listeners('error').length > 0 && this.emit('error', error);
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}
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this.emit('close');
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cb(null);
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});
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}, this.model.events);
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};
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/**
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* Get the next document from this cursor. Will return `null` when there are
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* no documents left.
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*
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* @param {Function} callback
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* @return {Promise}
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* @api public
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* @method next
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*/
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QueryCursor.prototype.next = function(callback) {
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return promiseOrCallback(callback, cb => {
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_next(this, function(error, doc) {
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if (error) {
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return cb(error);
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}
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cb(null, doc);
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});
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}, this.model.events);
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};
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/**
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* Execute `fn` for every document in the cursor. If `fn` returns a promise,
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* will wait for the promise to resolve before iterating on to the next one.
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* Returns a promise that resolves when done.
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*
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* ####Example
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*
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* // Iterate over documents asynchronously
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* Thing.
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* find({ name: /^hello/ }).
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* cursor().
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* eachAsync(async function (doc, i) {
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* doc.foo = doc.bar + i;
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* await doc.save();
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* })
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*
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* @param {Function} fn
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* @param {Object} [options]
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* @param {Number} [options.parallel] the number of promises to execute in parallel. Defaults to 1.
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* @param {Function} [callback] executed when all docs have been processed
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* @return {Promise}
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* @api public
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* @method eachAsync
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*/
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QueryCursor.prototype.eachAsync = function(fn, opts, callback) {
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const _this = this;
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if (typeof opts === 'function') {
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callback = opts;
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opts = {};
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}
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opts = opts || {};
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return eachAsync(function(cb) { return _next(_this, cb); }, fn, opts, callback);
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};
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/**
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* The `options` passed in to the `QueryCursor` constructor.
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*
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* @api public
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* @property options
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*/
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QueryCursor.prototype.options;
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/**
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* Adds a [cursor flag](http://mongodb.github.io/node-mongodb-native/2.2/api/Cursor.html#addCursorFlag).
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* Useful for setting the `noCursorTimeout` and `tailable` flags.
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*
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* @param {String} flag
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* @param {Boolean} value
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* @return {AggregationCursor} this
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* @api public
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* @method addCursorFlag
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*/
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QueryCursor.prototype.addCursorFlag = function(flag, value) {
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const _this = this;
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_waitForCursor(this, function() {
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_this.cursor.addCursorFlag(flag, value);
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});
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return this;
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};
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/*!
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* ignore
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*/
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QueryCursor.prototype.transformNull = function(val) {
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if (arguments.length === 0) {
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val = true;
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}
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this._mongooseOptions.transformNull = val;
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return this;
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};
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/*!
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* ignore
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*/
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QueryCursor.prototype._transformForAsyncIterator = function() {
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if (this._transforms.indexOf(_transformForAsyncIterator) === -1) {
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this.map(_transformForAsyncIterator);
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}
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return this;
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};
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/**
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* Returns an asyncIterator for use with [`for/await/of` loops](https://thecodebarbarian.com/getting-started-with-async-iterators-in-node-js).
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* You do not need to call this function explicitly, the JavaScript runtime
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* will call it for you.
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*
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* ####Example
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*
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* // Works without using `cursor()`
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* for await (const doc of Model.find([{ $sort: { name: 1 } }])) {
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* console.log(doc.name);
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* }
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*
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* // Can also use `cursor()`
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* for await (const doc of Model.find([{ $sort: { name: 1 } }]).cursor()) {
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* console.log(doc.name);
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* }
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*
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* Node.js 10.x supports async iterators natively without any flags. You can
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* enable async iterators in Node.js 8.x using the [`--harmony_async_iteration` flag](https://github.com/tc39/proposal-async-iteration/issues/117#issuecomment-346695187).
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*
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* **Note:** This function is not if `Symbol.asyncIterator` is undefined. If
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* `Symbol.asyncIterator` is undefined, that means your Node.js version does not
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* support async iterators.
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*
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* @method Symbol.asyncIterator
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* @memberOf Query
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* @instance
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* @api public
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*/
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if (Symbol.asyncIterator != null) {
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QueryCursor.prototype[Symbol.asyncIterator] = function() {
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return this.transformNull()._transformForAsyncIterator();
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};
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}
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/*!
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* ignore
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*/
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function _transformForAsyncIterator(doc) {
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return doc == null ? { done: true } : { value: doc, done: false };
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}
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/*!
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* Get the next doc from the underlying cursor and mongooseify it
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* (populate, etc.)
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*/
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function _next(ctx, cb) {
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let callback = cb;
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if (ctx._transforms.length) {
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callback = function(err, doc) {
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if (err || (doc === null && !ctx._mongooseOptions.transformNull)) {
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return cb(err, doc);
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}
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cb(err, ctx._transforms.reduce(function(doc, fn) {
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return fn.call(ctx, doc);
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}, doc));
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};
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}
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if (ctx._error) {
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return immediate(function() {
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callback(ctx._error);
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});
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}
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if (ctx.cursor) {
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if (ctx.query._mongooseOptions.populate && !ctx._pop) {
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ctx._pop = helpers.preparePopulationOptionsMQ(ctx.query,
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ctx.query._mongooseOptions);
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ctx._pop.__noPromise = true;
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}
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if (ctx.query._mongooseOptions.populate && ctx.options._populateBatchSize > 1) {
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if (ctx._batchDocs && ctx._batchDocs.length) {
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// Return a cached populated doc
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return _nextDoc(ctx, ctx._batchDocs.shift(), ctx._pop, callback);
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} else if (ctx._batchExhausted) {
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// Internal cursor reported no more docs. Act the same here
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return callback(null, null);
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} else {
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// Request as many docs as batchSize, to populate them also in batch
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ctx._batchDocs = [];
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return ctx.cursor.next(_onNext.bind({ ctx, callback }));
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}
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} else {
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return ctx.cursor.next(function(error, doc) {
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if (error) {
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return callback(error);
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}
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if (!doc) {
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return callback(null, null);
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}
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if (!ctx.query._mongooseOptions.populate) {
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return _nextDoc(ctx, doc, null, callback);
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}
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ctx.query.model.populate(doc, ctx._pop, function(err, doc) {
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if (err) {
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return callback(err);
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}
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return _nextDoc(ctx, doc, ctx._pop, callback);
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});
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});
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}
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} else {
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ctx.once('cursor', function(cursor) {
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if (cursor == null) {
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return;
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}
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_next(ctx, cb);
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});
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}
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}
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/*!
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* ignore
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*/
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function _onNext(error, doc) {
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if (error) {
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return this.callback(error);
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}
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if (!doc) {
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this.ctx._batchExhausted = true;
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return _populateBatch.call(this);
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}
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this.ctx._batchDocs.push(doc);
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if (this.ctx._batchDocs.length < this.ctx.options._populateBatchSize) {
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// If both `batchSize` and `_populateBatchSize` are huge, calling `next()` repeatedly may
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// cause a stack overflow. So make sure we clear the stack regularly.
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if (this.ctx._batchDocs.length > 0 && this.ctx._batchDocs.length % 1000 === 0) {
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return immediate(() => this.ctx.cursor.next(_onNext.bind(this)));
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}
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this.ctx.cursor.next(_onNext.bind(this));
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} else {
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_populateBatch.call(this);
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}
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}
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/*!
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* ignore
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*/
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function _populateBatch() {
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if (!this.ctx._batchDocs.length) {
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return this.callback(null, null);
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}
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const _this = this;
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this.ctx.query.model.populate(this.ctx._batchDocs, this.ctx._pop, function(err) {
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if (err) {
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return _this.callback(err);
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}
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_nextDoc(_this.ctx, _this.ctx._batchDocs.shift(), _this.ctx._pop, _this.callback);
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});
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}
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/*!
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* ignore
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*/
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function _nextDoc(ctx, doc, pop, callback) {
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if (ctx.query._mongooseOptions.lean) {
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return ctx.model.hooks.execPost('find', ctx.query, [[doc]], err => {
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if (err != null) {
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return callback(err);
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}
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callback(null, doc);
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});
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}
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_create(ctx, doc, pop, (err, doc) => {
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if (err != null) {
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return callback(err);
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}
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ctx.model.hooks.execPost('find', ctx.query, [[doc]], err => {
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if (err != null) {
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return callback(err);
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}
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callback(null, doc);
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});
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});
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}
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/*!
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* ignore
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*/
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function _waitForCursor(ctx, cb) {
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if (ctx.cursor) {
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return cb();
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}
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ctx.once('cursor', function(cursor) {
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if (cursor == null) {
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return;
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}
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cb();
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});
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}
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/*!
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* Convert a raw doc into a full mongoose doc.
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*/
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function _create(ctx, doc, populatedIds, cb) {
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const instance = helpers.createModel(ctx.query.model, doc, ctx.query._fields);
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const opts = populatedIds ?
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{ populated: populatedIds } :
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undefined;
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instance.init(doc, opts, function(err) {
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if (err) {
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return cb(err);
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}
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cb(null, instance);
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});
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}
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module.exports = QueryCursor;
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