api, login, auth

1 files changed, 3252 insertions, 0 deletions

diff --git a/node_modules/mquery/lib/mquery.js b/node_modules/mquery/lib/mquery.js
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+'use strict';
+
+/**
+ * Dependencies
+ */
+
+var slice = require('sliced');
+var assert = require('assert');
+var util = require('util');
+var utils = require('./utils');
+var debug = require('debug')('mquery');
+
+/* global Map */
+
+/**
+ * Query constructor used for building queries.
+ *
+ * ####Example:
+ *
+ *     var query = new Query({ name: 'mquery' });
+ *     query.setOptions({ collection: moduleCollection })
+ *     query.where('age').gte(21).exec(callback);
+ *
+ * @param {Object} [criteria]
+ * @param {Object} [options]
+ * @api public
+ */
+
+function Query(criteria, options) {
+  if (!(this instanceof Query))
+    return new Query(criteria, options);
+
+  var proto = this.constructor.prototype;
+
+  this.op = proto.op || undefined;
+
+  this.options = Object.assign({}, proto.options);
+
+  this._conditions = proto._conditions
+    ? utils.clone(proto._conditions)
+    : {};
+
+  this._fields = proto._fields
+    ? utils.clone(proto._fields)
+    : undefined;
+
+  this._update = proto._update
+    ? utils.clone(proto._update)
+    : undefined;
+
+  this._path = proto._path || undefined;
+  this._distinct = proto._distinct || undefined;
+  this._collection = proto._collection || undefined;
+  this._traceFunction = proto._traceFunction || undefined;
+
+  if (options) {
+    this.setOptions(options);
+  }
+
+  if (criteria) {
+    if (criteria.find && criteria.remove && criteria.update) {
+      // quack quack!
+      this.collection(criteria);
+    } else {
+      this.find(criteria);
+    }
+  }
+}
+
+/**
+ * This is a parameter that the user can set which determines if mquery
+ * uses $within or $geoWithin for queries. It defaults to true which
+ * means $geoWithin will be used. If using MongoDB < 2.4 you should
+ * set this to false.
+ *
+ * @api public
+ * @property use$geoWithin
+ */
+
+var $withinCmd = '$geoWithin';
+Object.defineProperty(Query, 'use$geoWithin', {
+  get: function( ) { return $withinCmd == '$geoWithin'; },
+  set: function(v) {
+    if (true === v) {
+      // mongodb >= 2.4
+      $withinCmd = '$geoWithin';
+    } else {
+      $withinCmd = '$within';
+    }
+  }
+});
+
+/**
+ * Converts this query to a constructor function with all arguments and options retained.
+ *
+ * ####Example
+ *
+ *     // Create a query that will read documents with a "video" category from
+ *     // `aCollection` on the primary node in the replica-set unless it is down,
+ *     // in which case we'll read from a secondary node.
+ *     var query = mquery({ category: 'video' })
+ *     query.setOptions({ collection: aCollection, read: 'primaryPreferred' });
+ *
+ *     // create a constructor based off these settings
+ *     var Video = query.toConstructor();
+ *
+ *     // Video is now a subclass of mquery() and works the same way but with the
+ *     // default query parameters and options set.
+ *
+ *     // run a query with the previous settings but filter for movies with names
+ *     // that start with "Life".
+ *     Video().where({ name: /^Life/ }).exec(cb);
+ *
+ * @return {Query} new Query
+ * @api public
+ */
+
+Query.prototype.toConstructor = function toConstructor() {
+  function CustomQuery(criteria, options) {
+    if (!(this instanceof CustomQuery))
+      return new CustomQuery(criteria, options);
+    Query.call(this, criteria, options);
+  }
+
+  utils.inherits(CustomQuery, Query);
+
+  // set inherited defaults
+  var p = CustomQuery.prototype;
+
+  p.options = {};
+  p.setOptions(this.options);
+
+  p.op = this.op;
+  p._conditions = utils.clone(this._conditions);
+  p._fields = utils.clone(this._fields);
+  p._update = utils.clone(this._update);
+  p._path = this._path;
+  p._distinct = this._distinct;
+  p._collection = this._collection;
+  p._traceFunction = this._traceFunction;
+
+  return CustomQuery;
+};
+
+/**
+ * Sets query options.
+ *
+ * ####Options:
+ *
+ * - [tailable](http://www.mongodb.org/display/DOCS/Tailable+Cursors) *
+ * - [sort](http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%7B%7Bsort(\)%7D%7D) *
+ * - [limit](http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%7B%7Blimit%28%29%7D%7D) *
+ * - [skip](http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%7B%7Bskip%28%29%7D%7D) *
+ * - [maxScan](http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24maxScan) *
+ * - [maxTime](http://docs.mongodb.org/manual/reference/operator/meta/maxTimeMS/#op._S_maxTimeMS) *
+ * - [batchSize](http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%7B%7BbatchSize%28%29%7D%7D) *
+ * - [comment](http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24comment) *
+ * - [snapshot](http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%7B%7Bsnapshot%28%29%7D%7D) *
+ * - [hint](http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24hint) *
+ * - [slaveOk](http://docs.mongodb.org/manual/applications/replication/#read-preference) *
+ * - [safe](http://www.mongodb.org/display/DOCS/getLastError+Command)
+ * - collection the collection to query against
+ *
+ * _* denotes a query helper method is also available_
+ *
+ * @param {Object} options
+ * @api public
+ */
+
+Query.prototype.setOptions = function(options) {
+  if (!(options && utils.isObject(options)))
+    return this;
+
+  // set arbitrary options
+  var methods = utils.keys(options),
+      method;
+
+  for (var i = 0; i < methods.length; ++i) {
+    method = methods[i];
+
+    // use methods if exist (safer option manipulation)
+    if ('function' == typeof this[method]) {
+      var args = utils.isArray(options[method])
+        ? options[method]
+        : [options[method]];
+      this[method].apply(this, args);
+    } else {
+      this.options[method] = options[method];
+    }
+  }
+
+  return this;
+};
+
+/**
+ * Sets this Querys collection.
+ *
+ * @param {Collection} coll
+ * @return {Query} this
+ */
+
+Query.prototype.collection = function collection(coll) {
+  this._collection = new Query.Collection(coll);
+
+  return this;
+};
+
+/**
+ * Adds a collation to this op (MongoDB 3.4 and up)
+ *
+ * ####Example
+ *
+ *     query.find().collation({ locale: "en_US", strength: 1 })
+ *
+ * @param {Object} value
+ * @return {Query} this
+ * @see MongoDB docs https://docs.mongodb.com/manual/reference/method/cursor.collation/#cursor.collation
+ * @api public
+ */
+
+Query.prototype.collation = function(value) {
+  this.options.collation = value;
+  return this;
+};
+
+/**
+ * Specifies a `$where` condition
+ *
+ * Use `$where` when you need to select documents using a JavaScript expression.
+ *
+ * ####Example
+ *
+ *     query.$where('this.comments.length > 10 || this.name.length > 5')
+ *
+ *     query.$where(function () {
+ *       return this.comments.length > 10 || this.name.length > 5;
+ *     })
+ *
+ * @param {String|Function} js javascript string or function
+ * @return {Query} this
+ * @memberOf Query
+ * @method $where
+ * @api public
+ */
+
+Query.prototype.$where = function(js) {
+  this._conditions.$where = js;
+  return this;
+};
+
+/**
+ * Specifies a `path` for use with chaining.
+ *
+ * ####Example
+ *
+ *     // instead of writing:
+ *     User.find({age: {$gte: 21, $lte: 65}}, callback);
+ *
+ *     // we can instead write:
+ *     User.where('age').gte(21).lte(65);
+ *
+ *     // passing query conditions is permitted
+ *     User.find().where({ name: 'vonderful' })
+ *
+ *     // chaining
+ *     User
+ *     .where('age').gte(21).lte(65)
+ *     .where('name', /^vonderful/i)
+ *     .where('friends').slice(10)
+ *     .exec(callback)
+ *
+ * @param {String} [path]
+ * @param {Object} [val]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.where = function() {
+  if (!arguments.length) return this;
+  if (!this.op) this.op = 'find';
+
+  var type = typeof arguments[0];
+
+  if ('string' == type) {
+    this._path = arguments[0];
+
+    if (2 === arguments.length) {
+      this._conditions[this._path] = arguments[1];
+    }
+
+    return this;
+  }
+
+  if ('object' == type && !Array.isArray(arguments[0])) {
+    return this.merge(arguments[0]);
+  }
+
+  throw new TypeError('path must be a string or object');
+};
+
+/**
+ * Specifies the complementary comparison value for paths specified with `where()`
+ *
+ * ####Example
+ *
+ *     User.where('age').equals(49);
+ *
+ *     // is the same as
+ *
+ *     User.where('age', 49);
+ *
+ * @param {Object} val
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.equals = function equals(val) {
+  this._ensurePath('equals');
+  var path = this._path;
+  this._conditions[path] = val;
+  return this;
+};
+
+/**
+ * Specifies the complementary comparison value for paths specified with `where()`
+ * This is alias of `equals`
+ *
+ * ####Example
+ *
+ *     User.where('age').eq(49);
+ *
+ *     // is the same as
+ *
+ *     User.shere('age').equals(49);
+ *
+ *     // is the same as
+ *
+ *     User.where('age', 49);
+ *
+ * @param {Object} val
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.eq = function eq(val) {
+  this._ensurePath('eq');
+  var path = this._path;
+  this._conditions[path] = val;
+  return this;
+};
+
+/**
+ * Specifies arguments for an `$or` condition.
+ *
+ * ####Example
+ *
+ *     query.or([{ color: 'red' }, { status: 'emergency' }])
+ *
+ * @param {Array} array array of conditions
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.or = function or(array) {
+  var or = this._conditions.$or || (this._conditions.$or = []);
+  if (!utils.isArray(array)) array = [array];
+  or.push.apply(or, array);
+  return this;
+};
+
+/**
+ * Specifies arguments for a `$nor` condition.
+ *
+ * ####Example
+ *
+ *     query.nor([{ color: 'green' }, { status: 'ok' }])
+ *
+ * @param {Array} array array of conditions
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.nor = function nor(array) {
+  var nor = this._conditions.$nor || (this._conditions.$nor = []);
+  if (!utils.isArray(array)) array = [array];
+  nor.push.apply(nor, array);
+  return this;
+};
+
+/**
+ * Specifies arguments for a `$and` condition.
+ *
+ * ####Example
+ *
+ *     query.and([{ color: 'green' }, { status: 'ok' }])
+ *
+ * @see $and http://docs.mongodb.org/manual/reference/operator/and/
+ * @param {Array} array array of conditions
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.and = function and(array) {
+  var and = this._conditions.$and || (this._conditions.$and = []);
+  if (!Array.isArray(array)) array = [array];
+  and.push.apply(and, array);
+  return this;
+};
+
+/**
+ * Specifies a $gt query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * ####Example
+ *
+ *     Thing.find().where('age').gt(21)
+ *
+ *     // or
+ *     Thing.find().gt('age', 21)
+ *
+ * @method gt
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {Number} val
+ * @api public
+ */
+
+/**
+ * Specifies a $gte query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * @method gte
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {Number} val
+ * @api public
+ */
+
+/**
+ * Specifies a $lt query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * @method lt
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {Number} val
+ * @api public
+ */
+
+/**
+ * Specifies a $lte query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * @method lte
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {Number} val
+ * @api public
+ */
+
+/**
+ * Specifies a $ne query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * @method ne
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {Number} val
+ * @api public
+ */
+
+/**
+ * Specifies an $in query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * @method in
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {Number} val
+ * @api public
+ */
+
+/**
+ * Specifies an $nin query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * @method nin
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {Number} val
+ * @api public
+ */
+
+/**
+ * Specifies an $all query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * @method all
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {Number} val
+ * @api public
+ */
+
+/**
+ * Specifies a $size query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * @method size
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {Number} val
+ * @api public
+ */
+
+/**
+ * Specifies a $regex query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * @method regex
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {String|RegExp} val
+ * @api public
+ */
+
+/**
+ * Specifies a $maxDistance query condition.
+ *
+ * When called with one argument, the most recent path passed to `where()` is used.
+ *
+ * @method maxDistance
+ * @memberOf Query
+ * @param {String} [path]
+ * @param {Number} val
+ * @api public
+ */
+
+/*!
+ * gt, gte, lt, lte, ne, in, nin, all, regex, size, maxDistance
+ *
+ *     Thing.where('type').nin(array)
+ */
+
+'gt gte lt lte ne in nin all regex size maxDistance minDistance'.split(' ').forEach(function($conditional) {
+  Query.prototype[$conditional] = function() {
+    var path, val;
+
+    if (1 === arguments.length) {
+      this._ensurePath($conditional);
+      val = arguments[0];
+      path = this._path;
+    } else {
+      val = arguments[1];
+      path = arguments[0];
+    }
+
+    var conds = this._conditions[path] === null || typeof this._conditions[path] === 'object' ?
+      this._conditions[path] :
+      (this._conditions[path] = {});
+    conds['$' + $conditional] = val;
+    return this;
+  };
+});
+
+/**
+ * Specifies a `$mod` condition
+ *
+ * @param {String} [path]
+ * @param {Number} val
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.mod = function() {
+  var val, path;
+
+  if (1 === arguments.length) {
+    this._ensurePath('mod');
+    val = arguments[0];
+    path = this._path;
+  } else if (2 === arguments.length && !utils.isArray(arguments[1])) {
+    this._ensurePath('mod');
+    val = slice(arguments);
+    path = this._path;
+  } else if (3 === arguments.length) {
+    val = slice(arguments, 1);
+    path = arguments[0];
+  } else {
+    val = arguments[1];
+    path = arguments[0];
+  }
+
+  var conds = this._conditions[path] || (this._conditions[path] = {});
+  conds.$mod = val;
+  return this;
+};
+
+/**
+ * Specifies an `$exists` condition
+ *
+ * ####Example
+ *
+ *     // { name: { $exists: true }}
+ *     Thing.where('name').exists()
+ *     Thing.where('name').exists(true)
+ *     Thing.find().exists('name')
+ *
+ *     // { name: { $exists: false }}
+ *     Thing.where('name').exists(false);
+ *     Thing.find().exists('name', false);
+ *
+ * @param {String} [path]
+ * @param {Number} val
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.exists = function() {
+  var path, val;
+
+  if (0 === arguments.length) {
+    this._ensurePath('exists');
+    path = this._path;
+    val = true;
+  } else if (1 === arguments.length) {
+    if ('boolean' === typeof arguments[0]) {
+      this._ensurePath('exists');
+      path = this._path;
+      val = arguments[0];
+    } else {
+      path = arguments[0];
+      val = true;
+    }
+  } else if (2 === arguments.length) {
+    path = arguments[0];
+    val = arguments[1];
+  }
+
+  var conds = this._conditions[path] || (this._conditions[path] = {});
+  conds.$exists = val;
+  return this;
+};
+
+/**
+ * Specifies an `$elemMatch` condition
+ *
+ * ####Example
+ *
+ *     query.elemMatch('comment', { author: 'autobot', votes: {$gte: 5}})
+ *
+ *     query.where('comment').elemMatch({ author: 'autobot', votes: {$gte: 5}})
+ *
+ *     query.elemMatch('comment', function (elem) {
+ *       elem.where('author').equals('autobot');
+ *       elem.where('votes').gte(5);
+ *     })
+ *
+ *     query.where('comment').elemMatch(function (elem) {
+ *       elem.where({ author: 'autobot' });
+ *       elem.where('votes').gte(5);
+ *     })
+ *
+ * @param {String|Object|Function} path
+ * @param {Object|Function} criteria
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.elemMatch = function() {
+  if (null == arguments[0])
+    throw new TypeError('Invalid argument');
+
+  var fn, path, criteria;
+
+  if ('function' === typeof arguments[0]) {
+    this._ensurePath('elemMatch');
+    path = this._path;
+    fn = arguments[0];
+  } else if (utils.isObject(arguments[0])) {
+    this._ensurePath('elemMatch');
+    path = this._path;
+    criteria = arguments[0];
+  } else if ('function' === typeof arguments[1]) {
+    path = arguments[0];
+    fn = arguments[1];
+  } else if (arguments[1] && utils.isObject(arguments[1])) {
+    path = arguments[0];
+    criteria = arguments[1];
+  } else {
+    throw new TypeError('Invalid argument');
+  }
+
+  if (fn) {
+    criteria = new Query;
+    fn(criteria);
+    criteria = criteria._conditions;
+  }
+
+  var conds = this._conditions[path] || (this._conditions[path] = {});
+  conds.$elemMatch = criteria;
+  return this;
+};
+
+// Spatial queries
+
+/**
+ * Sugar for geo-spatial queries.
+ *
+ * ####Example
+ *
+ *     query.within().box()
+ *     query.within().circle()
+ *     query.within().geometry()
+ *
+ *     query.where('loc').within({ center: [50,50], radius: 10, unique: true, spherical: true });
+ *     query.where('loc').within({ box: [[40.73, -73.9], [40.7, -73.988]] });
+ *     query.where('loc').within({ polygon: [[],[],[],[]] });
+ *
+ *     query.where('loc').within([], [], []) // polygon
+ *     query.where('loc').within([], []) // box
+ *     query.where('loc').within({ type: 'LineString', coordinates: [...] }); // geometry
+ *
+ * ####NOTE:
+ *
+ * Must be used after `where()`.
+ *
+ * @memberOf Query
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.within = function within() {
+  // opinionated, must be used after where
+  this._ensurePath('within');
+  this._geoComparison = $withinCmd;
+
+  if (0 === arguments.length) {
+    return this;
+  }
+
+  if (2 === arguments.length) {
+    return this.box.apply(this, arguments);
+  } else if (2 < arguments.length) {
+    return this.polygon.apply(this, arguments);
+  }
+
+  var area = arguments[0];
+
+  if (!area)
+    throw new TypeError('Invalid argument');
+
+  if (area.center)
+    return this.circle(area);
+
+  if (area.box)
+    return this.box.apply(this, area.box);
+
+  if (area.polygon)
+    return this.polygon.apply(this, area.polygon);
+
+  if (area.type && area.coordinates)
+    return this.geometry(area);
+
+  throw new TypeError('Invalid argument');
+};
+
+/**
+ * Specifies a $box condition
+ *
+ * ####Example
+ *
+ *     var lowerLeft = [40.73083, -73.99756]
+ *     var upperRight= [40.741404,  -73.988135]
+ *
+ *     query.where('loc').within().box(lowerLeft, upperRight)
+ *     query.box('loc', lowerLeft, upperRight )
+ *
+ * @see http://www.mongodb.org/display/DOCS/Geospatial+Indexing
+ * @see Query#within #query_Query-within
+ * @param {String} path
+ * @param {Object} val
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.box = function() {
+  var path, box;
+
+  if (3 === arguments.length) {
+    // box('loc', [], [])
+    path = arguments[0];
+    box = [arguments[1], arguments[2]];
+  } else if (2 === arguments.length) {
+    // box([], [])
+    this._ensurePath('box');
+    path = this._path;
+    box = [arguments[0], arguments[1]];
+  } else {
+    throw new TypeError('Invalid argument');
+  }
+
+  var conds = this._conditions[path] || (this._conditions[path] = {});
+  conds[this._geoComparison || $withinCmd] = { '$box': box };
+  return this;
+};
+
+/**
+ * Specifies a $polygon condition
+ *
+ * ####Example
+ *
+ *     query.where('loc').within().polygon([10,20], [13, 25], [7,15])
+ *     query.polygon('loc', [10,20], [13, 25], [7,15])
+ *
+ * @param {String|Array} [path]
+ * @param {Array|Object} [val]
+ * @return {Query} this
+ * @see http://www.mongodb.org/display/DOCS/Geospatial+Indexing
+ * @api public
+ */
+
+Query.prototype.polygon = function() {
+  var val, path;
+
+  if ('string' == typeof arguments[0]) {
+    // polygon('loc', [],[],[])
+    path = arguments[0];
+    val = slice(arguments, 1);
+  } else {
+    // polygon([],[],[])
+    this._ensurePath('polygon');
+    path = this._path;
+    val = slice(arguments);
+  }
+
+  var conds = this._conditions[path] || (this._conditions[path] = {});
+  conds[this._geoComparison || $withinCmd] = { '$polygon': val };
+  return this;
+};
+
+/**
+ * Specifies a $center or $centerSphere condition.
+ *
+ * ####Example
+ *
+ *     var area = { center: [50, 50], radius: 10, unique: true }
+ *     query.where('loc').within().circle(area)
+ *     query.center('loc', area);
+ *
+ *     // for spherical calculations
+ *     var area = { center: [50, 50], radius: 10, unique: true, spherical: true }
+ *     query.where('loc').within().circle(area)
+ *     query.center('loc', area);
+ *
+ * @param {String} [path]
+ * @param {Object} area
+ * @return {Query} this
+ * @see http://www.mongodb.org/display/DOCS/Geospatial+Indexing
+ * @api public
+ */
+
+Query.prototype.circle = function() {
+  var path, val;
+
+  if (1 === arguments.length) {
+    this._ensurePath('circle');
+    path = this._path;
+    val = arguments[0];
+  } else if (2 === arguments.length) {
+    path = arguments[0];
+    val = arguments[1];
+  } else {
+    throw new TypeError('Invalid argument');
+  }
+
+  if (!('radius' in val && val.center))
+    throw new Error('center and radius are required');
+
+  var conds = this._conditions[path] || (this._conditions[path] = {});
+
+  var type = val.spherical
+    ? '$centerSphere'
+    : '$center';
+
+  var wKey = this._geoComparison || $withinCmd;
+  conds[wKey] = {};
+  conds[wKey][type] = [val.center, val.radius];
+
+  if ('unique' in val)
+    conds[wKey].$uniqueDocs = !!val.unique;
+
+  return this;
+};
+
+/**
+ * Specifies a `$near` or `$nearSphere` condition
+ *
+ * These operators return documents sorted by distance.
+ *
+ * ####Example
+ *
+ *     query.where('loc').near({ center: [10, 10] });
+ *     query.where('loc').near({ center: [10, 10], maxDistance: 5 });
+ *     query.where('loc').near({ center: [10, 10], maxDistance: 5, spherical: true });
+ *     query.near('loc', { center: [10, 10], maxDistance: 5 });
+ *     query.near({ center: { type: 'Point', coordinates: [..] }})
+ *     query.near().geometry({ type: 'Point', coordinates: [..] })
+ *
+ * @param {String} [path]
+ * @param {Object} val
+ * @return {Query} this
+ * @see http://www.mongodb.org/display/DOCS/Geospatial+Indexing
+ * @api public
+ */
+
+Query.prototype.near = function near() {
+  var path, val;
+
+  this._geoComparison = '$near';
+
+  if (0 === arguments.length) {
+    return this;
+  } else if (1 === arguments.length) {
+    this._ensurePath('near');
+    path = this._path;
+    val = arguments[0];
+  } else if (2 === arguments.length) {
+    path = arguments[0];
+    val = arguments[1];
+  } else {
+    throw new TypeError('Invalid argument');
+  }
+
+  if (!val.center) {
+    throw new Error('center is required');
+  }
+
+  var conds = this._conditions[path] || (this._conditions[path] = {});
+
+  var type = val.spherical
+    ? '$nearSphere'
+    : '$near';
+
+  // center could be a GeoJSON object or an Array
+  if (Array.isArray(val.center)) {
+    conds[type] = val.center;
+
+    var radius = 'maxDistance' in val
+      ? val.maxDistance
+      : null;
+
+    if (null != radius) {
+      conds.$maxDistance = radius;
+    }
+    if (null != val.minDistance) {
+      conds.$minDistance = val.minDistance;
+    }
+  } else {
+    // GeoJSON?
+    if (val.center.type != 'Point' || !Array.isArray(val.center.coordinates)) {
+      throw new Error(util.format('Invalid GeoJSON specified for %s', type));
+    }
+    conds[type] = { $geometry : val.center };
+
+    // MongoDB 2.6 insists on maxDistance being in $near / $nearSphere
+    if ('maxDistance' in val) {
+      conds[type]['$maxDistance'] = val.maxDistance;
+    }
+    if ('minDistance' in val) {
+      conds[type]['$minDistance'] = val.minDistance;
+    }
+  }
+
+  return this;
+};
+
+/**
+ * Declares an intersects query for `geometry()`.
+ *
+ * ####Example
+ *
+ *     query.where('path').intersects().geometry({
+ *         type: 'LineString'
+ *       , coordinates: [[180.0, 11.0], [180, 9.0]]
+ *     })
+ *
+ *     query.where('path').intersects({
+ *         type: 'LineString'
+ *       , coordinates: [[180.0, 11.0], [180, 9.0]]
+ *     })
+ *
+ * @param {Object} [arg]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.intersects = function intersects() {
+  // opinionated, must be used after where
+  this._ensurePath('intersects');
+
+  this._geoComparison = '$geoIntersects';
+
+  if (0 === arguments.length) {
+    return this;
+  }
+
+  var area = arguments[0];
+
+  if (null != area && area.type && area.coordinates)
+    return this.geometry(area);
+
+  throw new TypeError('Invalid argument');
+};
+
+/**
+ * Specifies a `$geometry` condition
+ *
+ * ####Example
+ *
+ *     var polyA = [[[ 10, 20 ], [ 10, 40 ], [ 30, 40 ], [ 30, 20 ]]]
+ *     query.where('loc').within().geometry({ type: 'Polygon', coordinates: polyA })
+ *
+ *     // or
+ *     var polyB = [[ 0, 0 ], [ 1, 1 ]]
+ *     query.where('loc').within().geometry({ type: 'LineString', coordinates: polyB })
+ *
+ *     // or
+ *     var polyC = [ 0, 0 ]
+ *     query.where('loc').within().geometry({ type: 'Point', coordinates: polyC })
+ *
+ *     // or
+ *     query.where('loc').intersects().geometry({ type: 'Point', coordinates: polyC })
+ *
+ * ####NOTE:
+ *
+ * `geometry()` **must** come after either `intersects()` or `within()`.
+ *
+ * The `object` argument must contain `type` and `coordinates` properties.
+ * - type {String}
+ * - coordinates {Array}
+ *
+ * The most recent path passed to `where()` is used.
+ *
+ * @param {Object} object Must contain a `type` property which is a String and a `coordinates` property which is an Array. See the examples.
+ * @return {Query} this
+ * @see http://docs.mongodb.org/manual/release-notes/2.4/#new-geospatial-indexes-with-geojson-and-improved-spherical-geometry
+ * @see http://www.mongodb.org/display/DOCS/Geospatial+Indexing
+ * @see $geometry http://docs.mongodb.org/manual/reference/operator/geometry/
+ * @api public
+ */
+
+Query.prototype.geometry = function geometry() {
+  if (!('$within' == this._geoComparison ||
+        '$geoWithin' == this._geoComparison ||
+        '$near' == this._geoComparison ||
+        '$geoIntersects' == this._geoComparison)) {
+    throw new Error('geometry() must come after `within()`, `intersects()`, or `near()');
+  }
+
+  var val, path;
+
+  if (1 === arguments.length) {
+    this._ensurePath('geometry');
+    path = this._path;
+    val = arguments[0];
+  } else {
+    throw new TypeError('Invalid argument');
+  }
+
+  if (!(val.type && Array.isArray(val.coordinates))) {
+    throw new TypeError('Invalid argument');
+  }
+
+  var conds = this._conditions[path] || (this._conditions[path] = {});
+  conds[this._geoComparison] = { $geometry: val };
+
+  return this;
+};
+
+// end spatial
+
+/**
+ * Specifies which document fields to include or exclude
+ *
+ * ####String syntax
+ *
+ * When passing a string, prefixing a path with `-` will flag that path as excluded. When a path does not have the `-` prefix, it is included.
+ *
+ * ####Example
+ *
+ *     // include a and b, exclude c
+ *     query.select('a b -c');
+ *
+ *     // or you may use object notation, useful when
+ *     // you have keys already prefixed with a "-"
+ *     query.select({a: 1, b: 1, c: 0});
+ *
+ * ####Note
+ *
+ * Cannot be used with `distinct()`
+ *
+ * @param {Object|String} arg
+ * @return {Query} this
+ * @see SchemaType
+ * @api public
+ */
+
+Query.prototype.select = function select() {
+  var arg = arguments[0];
+  if (!arg) return this;
+
+  if (arguments.length !== 1) {
+    throw new Error('Invalid select: select only takes 1 argument');
+  }
+
+  this._validate('select');
+
+  var fields = this._fields || (this._fields = {});
+  var type = typeof arg;
+  var i, len;
+
+  if (('string' == type || utils.isArgumentsObject(arg)) &&
+    'number' == typeof arg.length || Array.isArray(arg)) {
+    if ('string' == type)
+      arg = arg.split(/\s+/);
+
+    for (i = 0, len = arg.length; i < len; ++i) {
+      var field = arg[i];
+      if (!field) continue;
+      var include = '-' == field[0] ? 0 : 1;
+      if (include === 0) field = field.substring(1);
+      fields[field] = include;
+    }
+
+    return this;
+  }
+
+  if (utils.isObject(arg)) {
+    var keys = utils.keys(arg);
+    for (i = 0; i < keys.length; ++i) {
+      fields[keys[i]] = arg[keys[i]];
+    }
+    return this;
+  }
+
+  throw new TypeError('Invalid select() argument. Must be string or object.');
+};
+
+/**
+ * Specifies a $slice condition for a `path`
+ *
+ * ####Example
+ *
+ *     query.slice('comments', 5)
+ *     query.slice('comments', -5)
+ *     query.slice('comments', [10, 5])
+ *     query.where('comments').slice(5)
+ *     query.where('comments').slice([-10, 5])
+ *
+ * @param {String} [path]
+ * @param {Number} val number/range of elements to slice
+ * @return {Query} this
+ * @see mongodb http://www.mongodb.org/display/DOCS/Retrieving+a+Subset+of+Fields#RetrievingaSubsetofFields-RetrievingaSubrangeofArrayElements
+ * @api public
+ */
+
+Query.prototype.slice = function() {
+  if (0 === arguments.length)
+    return this;
+
+  this._validate('slice');
+
+  var path, val;
+
+  if (1 === arguments.length) {
+    var arg = arguments[0];
+    if (typeof arg === 'object' && !Array.isArray(arg)) {
+      var keys = Object.keys(arg);
+      var numKeys = keys.length;
+      for (var i = 0; i < numKeys; ++i) {
+        this.slice(keys[i], arg[keys[i]]);
+      }
+      return this;
+    }
+    this._ensurePath('slice');
+    path = this._path;
+    val = arguments[0];
+  } else if (2 === arguments.length) {
+    if ('number' === typeof arguments[0]) {
+      this._ensurePath('slice');
+      path = this._path;
+      val = slice(arguments);
+    } else {
+      path = arguments[0];
+      val = arguments[1];
+    }
+  } else if (3 === arguments.length) {
+    path = arguments[0];
+    val = slice(arguments, 1);
+  }
+
+  var myFields = this._fields || (this._fields = {});
+  myFields[path] = { '$slice': val };
+  return this;
+};
+
+/**
+ * Sets the sort order
+ *
+ * If an object is passed, values allowed are 'asc', 'desc', 'ascending', 'descending', 1, and -1.
+ *
+ * If a string is passed, it must be a space delimited list of path names. The sort order of each path is ascending unless the path name is prefixed with `-` which will be treated as descending.
+ *
+ * ####Example
+ *
+ *     // these are equivalent
+ *     query.sort({ field: 'asc', test: -1 });
+ *     query.sort('field -test');
+ *     query.sort([['field', 1], ['test', -1]]);
+ *
+ * ####Note
+ *
+ *  - The array syntax `.sort([['field', 1], ['test', -1]])` can only be used with [mongodb driver >= 2.0.46](https://github.com/mongodb/node-mongodb-native/blob/2.1/HISTORY.md#2046-2015-10-15).
+ *  - Cannot be used with `distinct()`
+ *
+ * @param {Object|String|Array} arg
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.sort = function(arg) {
+  if (!arg) return this;
+  var i, len, field;
+
+  this._validate('sort');
+
+  var type = typeof arg;
+
+  // .sort([['field', 1], ['test', -1]])
+  if (Array.isArray(arg)) {
+    len = arg.length;
+    for (i = 0; i < arg.length; ++i) {
+      if (!Array.isArray(arg[i])) {
+        throw new Error('Invalid sort() argument, must be array of arrays');
+      }
+      _pushArr(this.options, arg[i][0], arg[i][1]);
+    }
+    return this;
+  }
+
+  // .sort('field -test')
+  if (1 === arguments.length && 'string' == type) {
+    arg = arg.split(/\s+/);
+    len = arg.length;
+    for (i = 0; i < len; ++i) {
+      field = arg[i];
+      if (!field) continue;
+      var ascend = '-' == field[0] ? -1 : 1;
+      if (ascend === -1) field = field.substring(1);
+      push(this.options, field, ascend);
+    }
+
+    return this;
+  }
+
+  // .sort({ field: 1, test: -1 })
+  if (utils.isObject(arg)) {
+    var keys = utils.keys(arg);
+    for (i = 0; i < keys.length; ++i) {
+      field = keys[i];
+      push(this.options, field, arg[field]);
+    }
+
+    return this;
+  }
+
+  if (typeof Map !== 'undefined' && arg instanceof Map) {
+    _pushMap(this.options, arg);
+    return this;
+  }
+  throw new TypeError('Invalid sort() argument. Must be a string, object, or array.');
+};
+
+/*!
+ * @ignore
+ */
+
+var _validSortValue = {
+  '1': 1,
+  '-1': -1,
+  'asc': 1,
+  'ascending': 1,
+  'desc': -1,
+  'descending': -1
+};
+
+function push(opts, field, value) {
+  if (Array.isArray(opts.sort)) {
+    throw new TypeError('Can\'t mix sort syntaxes. Use either array or object:' +
+      '\n- `.sort([[\'field\', 1], [\'test\', -1]])`' +
+      '\n- `.sort({ field: 1, test: -1 })`');
+  }
+
+  var s;
+  if (value && value.$meta) {
+    s = opts.sort || (opts.sort = {});
+    s[field] = { $meta : value.$meta };
+    return;
+  }
+
+  s = opts.sort || (opts.sort = {});
+  var val = String(value || 1).toLowerCase();
+  val = _validSortValue[val];
+  if (!val) throw new TypeError('Invalid sort value: { ' + field + ': ' + value + ' }');
+
+  s[field] = val;
+}
+
+function _pushArr(opts, field, value) {
+  opts.sort = opts.sort || [];
+  if (!Array.isArray(opts.sort)) {
+    throw new TypeError('Can\'t mix sort syntaxes. Use either array or object:' +
+      '\n- `.sort([[\'field\', 1], [\'test\', -1]])`' +
+      '\n- `.sort({ field: 1, test: -1 })`');
+  }
+
+  var val = String(value || 1).toLowerCase();
+  val = _validSortValue[val];
+  if (!val) throw new TypeError('Invalid sort value: [ ' + field + ', ' + value + ' ]');
+
+  opts.sort.push([field, val]);
+}
+
+function _pushMap(opts, map) {
+  opts.sort = opts.sort || new Map();
+  if (!(opts.sort instanceof Map)) {
+    throw new TypeError('Can\'t mix sort syntaxes. Use either array or ' +
+      'object or map consistently');
+  }
+  map.forEach(function(value, key) {
+    var val = String(value || 1).toLowerCase();
+    val = _validSortValue[val];
+    if (!val) throw new TypeError('Invalid sort value: < ' + key + ': ' + value + ' >');
+
+    opts.sort.set(key, val);
+  });
+}
+
+
+
+/**
+ * Specifies the limit option.
+ *
+ * ####Example
+ *
+ *     query.limit(20)
+ *
+ * ####Note
+ *
+ * Cannot be used with `distinct()`
+ *
+ * @method limit
+ * @memberOf Query
+ * @param {Number} val
+ * @see mongodb http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%7B%7Blimit%28%29%7D%7D
+ * @api public
+ */
+/**
+ * Specifies the skip option.
+ *
+ * ####Example
+ *
+ *     query.skip(100).limit(20)
+ *
+ * ####Note
+ *
+ * Cannot be used with `distinct()`
+ *
+ * @method skip
+ * @memberOf Query
+ * @param {Number} val
+ * @see mongodb http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%7B%7Bskip%28%29%7D%7D
+ * @api public
+ */
+/**
+ * Specifies the maxScan option.
+ *
+ * ####Example
+ *
+ *     query.maxScan(100)
+ *
+ * ####Note
+ *
+ * Cannot be used with `distinct()`
+ *
+ * @method maxScan
+ * @memberOf Query
+ * @param {Number} val
+ * @see mongodb http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24maxScan
+ * @api public
+ */
+/**
+ * Specifies the batchSize option.
+ *
+ * ####Example
+ *
+ *     query.batchSize(100)
+ *
+ * ####Note
+ *
+ * Cannot be used with `distinct()`
+ *
+ * @method batchSize
+ * @memberOf Query
+ * @param {Number} val
+ * @see mongodb http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%7B%7BbatchSize%28%29%7D%7D
+ * @api public
+ */
+/**
+ * Specifies the `comment` option.
+ *
+ * ####Example
+ *
+ *     query.comment('login query')
+ *
+ * ####Note
+ *
+ * Cannot be used with `distinct()`
+ *
+ * @method comment
+ * @memberOf Query
+ * @param {Number} val
+ * @see mongodb http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24comment
+ * @api public
+ */
+
+/*!
+ * limit, skip, maxScan, batchSize, comment
+ *
+ * Sets these associated options.
+ *
+ *     query.comment('feed query');
+ */
+
+['limit', 'skip', 'maxScan', 'batchSize', 'comment'].forEach(function(method) {
+  Query.prototype[method] = function(v) {
+    this._validate(method);
+    this.options[method] = v;
+    return this;
+  };
+});
+
+/**
+ * Specifies the maxTimeMS option.
+ *
+ * ####Example
+ *
+ *     query.maxTime(100)
+ *     query.maxTimeMS(100)
+ *
+ * @method maxTime
+ * @memberOf Query
+ * @param {Number} ms
+ * @see mongodb http://docs.mongodb.org/manual/reference/operator/meta/maxTimeMS/#op._S_maxTimeMS
+ * @api public
+ */
+
+Query.prototype.maxTime = Query.prototype.maxTimeMS = function(ms) {
+  this._validate('maxTime');
+  this.options.maxTimeMS = ms;
+  return this;
+};
+
+/**
+ * Specifies this query as a `snapshot` query.
+ *
+ * ####Example
+ *
+ *     mquery().snapshot() // true
+ *     mquery().snapshot(true)
+ *     mquery().snapshot(false)
+ *
+ * ####Note
+ *
+ * Cannot be used with `distinct()`
+ *
+ * @see mongodb http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%7B%7Bsnapshot%28%29%7D%7D
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.snapshot = function() {
+  this._validate('snapshot');
+
+  this.options.snapshot = arguments.length
+    ? !!arguments[0]
+    : true;
+
+  return this;
+};
+
+/**
+ * Sets query hints.
+ *
+ * ####Example
+ *
+ *     query.hint({ indexA: 1, indexB: -1});
+ *     query.hint('indexA_1_indexB_1');
+ *
+ * ####Note
+ *
+ * Cannot be used with `distinct()`
+ *
+ * @param {Object|string} val a hint object or the index name
+ * @return {Query} this
+ * @see mongodb http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24hint
+ * @api public
+ */
+
+Query.prototype.hint = function() {
+  if (0 === arguments.length) return this;
+
+  this._validate('hint');
+
+  var arg = arguments[0];
+  if (utils.isObject(arg)) {
+    var hint = this.options.hint || (this.options.hint = {});
+
+    // must keep object keys in order so don't use Object.keys()
+    for (var k in arg) {
+      hint[k] = arg[k];
+    }
+
+    return this;
+  }
+  if (typeof arg === 'string') {
+    this.options.hint = arg;
+    return this;
+  }
+
+  throw new TypeError('Invalid hint. ' + arg);
+};
+
+/**
+ * Requests acknowledgement that this operation has been persisted to MongoDB's
+ * on-disk journal.
+ * This option is only valid for operations that write to the database:
+ *
+ * - `deleteOne()`
+ * - `deleteMany()`
+ * - `findOneAndDelete()`
+ * - `findOneAndUpdate()`
+ * - `remove()`
+ * - `update()`
+ * - `updateOne()`
+ * - `updateMany()`
+ *
+ * Defaults to the `j` value if it is specified in writeConcern options
+ *
+ * ####Example:
+ *
+ *     mquery().w(2).j(true).wtimeout(2000);
+ *
+ * @method j
+ * @memberOf Query
+ * @instance
+ * @param {boolean} val
+ * @see mongodb https://docs.mongodb.com/manual/reference/write-concern/#j-option
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.j = function j(val) {
+  this.options.j = val;
+  return this;
+};
+
+/**
+ * Sets the slaveOk option. _Deprecated_ in MongoDB 2.2 in favor of read preferences.
+ *
+ * ####Example:
+ *
+ *     query.slaveOk() // true
+ *     query.slaveOk(true)
+ *     query.slaveOk(false)
+ *
+ * @deprecated use read() preferences instead if on mongodb >= 2.2
+ * @param {Boolean} v defaults to true
+ * @see mongodb http://docs.mongodb.org/manual/applications/replication/#read-preference
+ * @see read()
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.slaveOk = function(v) {
+  this.options.slaveOk = arguments.length ? !!v : true;
+  return this;
+};
+
+/**
+ * Sets the readPreference option for the query.
+ *
+ * ####Example:
+ *
+ *     new Query().read('primary')
+ *     new Query().read('p')  // same as primary
+ *
+ *     new Query().read('primaryPreferred')
+ *     new Query().read('pp') // same as primaryPreferred
+ *
+ *     new Query().read('secondary')
+ *     new Query().read('s')  // same as secondary
+ *
+ *     new Query().read('secondaryPreferred')
+ *     new Query().read('sp') // same as secondaryPreferred
+ *
+ *     new Query().read('nearest')
+ *     new Query().read('n')  // same as nearest
+ *
+ *     // you can also use mongodb.ReadPreference class to also specify tags
+ *     new Query().read(mongodb.ReadPreference('secondary', [{ dc:'sf', s: 1 },{ dc:'ma', s: 2 }]))
+ *
+ *     new Query().setReadPreference('primary') // alias of .read()
+ *
+ * ####Preferences:
+ *
+ *     primary - (default)  Read from primary only. Operations will produce an error if primary is unavailable. Cannot be combined with tags.
+ *     secondary            Read from secondary if available, otherwise error.
+ *     primaryPreferred     Read from primary if available, otherwise a secondary.
+ *     secondaryPreferred   Read from a secondary if available, otherwise read from the primary.
+ *     nearest              All operations read from among the nearest candidates, but unlike other modes, this option will include both the primary and all secondaries in the random selection.
+ *
+ * Aliases
+ *
+ *     p   primary
+ *     pp  primaryPreferred
+ *     s   secondary
+ *     sp  secondaryPreferred
+ *     n   nearest
+ *
+ * Read more about how to use read preferences [here](http://docs.mongodb.org/manual/applications/replication/#read-preference) and [here](http://mongodb.github.com/node-mongodb-native/driver-articles/anintroductionto1_1and2_2.html#read-preferences).
+ *
+ * @param {String|ReadPreference} pref one of the listed preference options or their aliases
+ * @see mongodb http://docs.mongodb.org/manual/applications/replication/#read-preference
+ * @see driver http://mongodb.github.com/node-mongodb-native/driver-articles/anintroductionto1_1and2_2.html#read-preferences
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.read = Query.prototype.setReadPreference = function(pref) {
+  if (arguments.length > 1 && !Query.prototype.read.deprecationWarningIssued) {
+    console.error('Deprecation warning: \'tags\' argument is not supported anymore in Query.read() method. Please use mongodb.ReadPreference object instead.');
+    Query.prototype.read.deprecationWarningIssued = true;
+  }
+  this.options.readPreference = utils.readPref(pref);
+  return this;
+};
+
+/**
+ * Sets the readConcern option for the query.
+ *
+ * ####Example:
+ *
+ *     new Query().readConcern('local')
+ *     new Query().readConcern('l')  // same as local
+ *
+ *     new Query().readConcern('available')
+ *     new Query().readConcern('a')  // same as available
+ *
+ *     new Query().readConcern('majority')
+ *     new Query().readConcern('m')  // same as majority
+ *
+ *     new Query().readConcern('linearizable')
+ *     new Query().readConcern('lz') // same as linearizable
+ *
+ *     new Query().readConcern('snapshot')
+ *     new Query().readConcern('s')  // same as snapshot
+ *
+ *     new Query().r('s') // r is alias of readConcern
+ *
+ *
+ * ####Read Concern Level:
+ *
+ *     local         MongoDB 3.2+ The query returns from the instance with no guarantee guarantee that the data has been written to a majority of the replica set members (i.e. may be rolled back).
+ *     available     MongoDB 3.6+ The query returns from the instance with no guarantee guarantee that the data has been written to a majority of the replica set members (i.e. may be rolled back).
+ *     majority      MongoDB 3.2+ The query returns the data that has been acknowledged by a majority of the replica set members. The documents returned by the read operation are durable, even in the event of failure.
+ *     linearizable  MongoDB 3.4+ The query returns data that reflects all successful majority-acknowledged writes that completed prior to the start of the read operation. The query may wait for concurrently executing writes to propagate to a majority of replica set members before returning results.
+ *     snapshot      MongoDB 4.0+ Only available for operations within multi-document transactions. Upon transaction commit with write concern "majority", the transaction operations are guaranteed to have read from a snapshot of majority-committed data.
+
+
+ *
+ *
+ * Aliases
+ *
+ *     l   local
+ *     a   available
+ *     m   majority
+ *     lz  linearizable
+ *     s   snapshot
+ *
+ * Read more about how to use read concern [here](https://docs.mongodb.com/manual/reference/read-concern/).
+ *
+ * @param {String} level one of the listed read concern level or their aliases
+ * @see mongodb https://docs.mongodb.com/manual/reference/read-concern/
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.readConcern = Query.prototype.r = function(level) {
+  this.options.readConcern = utils.readConcern(level);
+  return this;
+};
+
+/**
+ * Sets tailable option.
+ *
+ * ####Example
+ *
+ *     query.tailable() <== true
+ *     query.tailable(true)
+ *     query.tailable(false)
+ *
+ * ####Note
+ *
+ * Cannot be used with `distinct()`
+ *
+ * @param {Boolean} v defaults to true
+ * @see mongodb http://www.mongodb.org/display/DOCS/Tailable+Cursors
+ * @api public
+ */
+
+Query.prototype.tailable = function() {
+  this._validate('tailable');
+
+  this.options.tailable = arguments.length
+    ? !!arguments[0]
+    : true;
+
+  return this;
+};
+
+/**
+ * Sets the specified number of `mongod` servers, or tag set of `mongod` servers,
+ * that must acknowledge this write before this write is considered successful.
+ * This option is only valid for operations that write to the database:
+ *
+ * - `deleteOne()`
+ * - `deleteMany()`
+ * - `findOneAndDelete()`
+ * - `findOneAndUpdate()`
+ * - `remove()`
+ * - `update()`
+ * - `updateOne()`
+ * - `updateMany()`
+ *
+ * Defaults to the `w` value if it is specified in writeConcern options
+ *
+ * ####Example:
+ *
+ * mquery().writeConcern(0)
+ * mquery().writeConcern(1)
+ * mquery().writeConcern({ w: 1, j: true, wtimeout: 2000 })
+ * mquery().writeConcern('majority')
+ * mquery().writeConcern('m') // same as majority
+ * mquery().writeConcern('tagSetName') // if the tag set is 'm', use .writeConcern({ w: 'm' }) instead
+ * mquery().w(1) // w is alias of writeConcern
+ *
+ * @method writeConcern
+ * @memberOf Query
+ * @instance
+ * @param {String|number|object} concern 0 for fire-and-forget, 1 for acknowledged by one server, 'majority' for majority of the replica set, or [any of the more advanced options](https://docs.mongodb.com/manual/reference/write-concern/#w-option).
+ * @see mongodb https://docs.mongodb.com/manual/reference/write-concern/#w-option
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.writeConcern = Query.prototype.w = function writeConcern(concern) {
+  if ('object' === typeof concern) {
+    if ('undefined' !== typeof concern.j) this.options.j = concern.j;
+    if ('undefined' !== typeof concern.w) this.options.w = concern.w;
+    if ('undefined' !== typeof concern.wtimeout) this.options.wtimeout = concern.wtimeout;
+  } else {
+    this.options.w = 'm' === concern ? 'majority' : concern;
+  }
+  return this;
+};
+
+/**
+ * Specifies a time limit, in milliseconds, for the write concern.
+ * If `ms > 1`, it is maximum amount of time to wait for this write
+ * to propagate through the replica set before this operation fails.
+ * The default is `0`, which means no timeout.
+ *
+ * This option is only valid for operations that write to the database:
+ *
+ * - `deleteOne()`
+ * - `deleteMany()`
+ * - `findOneAndDelete()`
+ * - `findOneAndUpdate()`
+ * - `remove()`
+ * - `update()`
+ * - `updateOne()`
+ * - `updateMany()`
+ *
+ * Defaults to `wtimeout` value if it is specified in writeConcern
+ *
+ * ####Example:
+ *
+ *     mquery().w(2).j(true).wtimeout(2000)
+ *
+ * @method wtimeout
+ * @memberOf Query
+ * @instance
+ * @param {number} ms number of milliseconds to wait
+ * @see mongodb https://docs.mongodb.com/manual/reference/write-concern/#wtimeout
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.wtimeout = Query.prototype.wTimeout = function wtimeout(ms) {
+  this.options.wtimeout = ms;
+  return this;
+};
+
+/**
+ * Merges another Query or conditions object into this one.
+ *
+ * When a Query is passed, conditions, field selection and options are merged.
+ *
+ * @param {Query|Object} source
+ * @return {Query} this
+ */
+
+Query.prototype.merge = function(source) {
+  if (!source)
+    return this;
+
+  if (!Query.canMerge(source))
+    throw new TypeError('Invalid argument. Expected instanceof mquery or plain object');
+
+  if (source instanceof Query) {
+    // if source has a feature, apply it to ourselves
+
+    if (source._conditions) {
+      utils.merge(this._conditions, source._conditions);
+    }
+
+    if (source._fields) {
+      this._fields || (this._fields = {});
+      utils.merge(this._fields, source._fields);
+    }
+
+    if (source.options) {
+      this.options || (this.options = {});
+      utils.merge(this.options, source.options);
+    }
+
+    if (source._update) {
+      this._update || (this._update = {});
+      utils.mergeClone(this._update, source._update);
+    }
+
+    if (source._distinct) {
+      this._distinct = source._distinct;
+    }
+
+    return this;
+  }
+
+  // plain object
+  utils.merge(this._conditions, source);
+
+  return this;
+};
+
+/**
+ * Finds documents.
+ *
+ * Passing a `callback` executes the query.
+ *
+ * ####Example
+ *
+ *     query.find()
+ *     query.find(callback)
+ *     query.find({ name: 'Burning Lights' }, callback)
+ *
+ * @param {Object} [criteria] mongodb selector
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.find = function(criteria, callback) {
+  this.op = 'find';
+
+  if ('function' === typeof criteria) {
+    callback = criteria;
+    criteria = undefined;
+  } else if (Query.canMerge(criteria)) {
+    this.merge(criteria);
+  }
+
+  if (!callback) return this;
+
+  var conds = this._conditions;
+  var options = this._optionsForExec();
+
+  if (this.$useProjection) {
+    options.projection = this._fieldsForExec();
+  } else {
+    options.fields = this._fieldsForExec();
+  }
+
+  debug('find', this._collection.collectionName, conds, options);
+  callback = this._wrapCallback('find', callback, {
+    conditions: conds,
+    options: options
+  });
+
+  this._collection.find(conds, options, utils.tick(callback));
+  return this;
+};
+
+/**
+ * Returns the query cursor
+ *
+ * ####Examples
+ *
+ *     query.find().cursor();
+ *     query.cursor({ name: 'Burning Lights' });
+ *
+ * @param {Object} [criteria] mongodb selector
+ * @return {Object} cursor
+ * @api public
+ */
+
+Query.prototype.cursor = function cursor(criteria) {
+  if (this.op) {
+    if (this.op !== 'find') {
+      throw new TypeError('.cursor only support .find method');
+    }
+  } else {
+    this.find(criteria);
+  }
+
+  var conds = this._conditions;
+  var options = this._optionsForExec();
+
+  if (this.$useProjection) {
+    options.projection = this._fieldsForExec();
+  } else {
+    options.fields = this._fieldsForExec();
+  }
+
+  debug('findCursor', this._collection.collectionName, conds, options);
+  return this._collection.findCursor(conds, options);
+};
+
+/**
+ * Executes the query as a findOne() operation.
+ *
+ * Passing a `callback` executes the query.
+ *
+ * ####Example
+ *
+ *     query.findOne().where('name', /^Burning/);
+ *
+ *     query.findOne({ name: /^Burning/ })
+ *
+ *     query.findOne({ name: /^Burning/ }, callback); // executes
+ *
+ *     query.findOne(function (err, doc) {
+ *       if (err) return handleError(err);
+ *       if (doc) {
+ *         // doc may be null if no document matched
+ *
+ *       }
+ *     });
+ *
+ * @param {Object|Query} [criteria] mongodb selector
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.findOne = function(criteria, callback) {
+  this.op = 'findOne';
+
+  if ('function' === typeof criteria) {
+    callback = criteria;
+    criteria = undefined;
+  } else if (Query.canMerge(criteria)) {
+    this.merge(criteria);
+  }
+
+  if (!callback) return this;
+
+  var conds = this._conditions;
+  var options = this._optionsForExec();
+
+  if (this.$useProjection) {
+    options.projection = this._fieldsForExec();
+  } else {
+    options.fields = this._fieldsForExec();
+  }
+
+  debug('findOne', this._collection.collectionName, conds, options);
+  callback = this._wrapCallback('findOne', callback, {
+    conditions: conds,
+    options: options
+  });
+
+  this._collection.findOne(conds, options, utils.tick(callback));
+
+  return this;
+};
+
+/**
+ * Exectues the query as a count() operation.
+ *
+ * Passing a `callback` executes the query.
+ *
+ * ####Example
+ *
+ *     query.count().where('color', 'black').exec(callback);
+ *
+ *     query.count({ color: 'black' }).count(callback)
+ *
+ *     query.count({ color: 'black' }, callback)
+ *
+ *     query.where('color', 'black').count(function (err, count) {
+ *       if (err) return handleError(err);
+ *       console.log('there are %d kittens', count);
+ *     })
+ *
+ * @param {Object} [criteria] mongodb selector
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @see mongodb http://www.mongodb.org/display/DOCS/Aggregation#Aggregation-Count
+ * @api public
+ */
+
+Query.prototype.count = function(criteria, callback) {
+  this.op = 'count';
+  this._validate();
+
+  if ('function' === typeof criteria) {
+    callback = criteria;
+    criteria = undefined;
+  } else if (Query.canMerge(criteria)) {
+    this.merge(criteria);
+  }
+
+  if (!callback) return this;
+
+  var conds = this._conditions,
+      options = this._optionsForExec();
+
+  debug('count', this._collection.collectionName, conds, options);
+  callback = this._wrapCallback('count', callback, {
+    conditions: conds,
+    options: options
+  });
+
+  this._collection.count(conds, options, utils.tick(callback));
+  return this;
+};
+
+/**
+ * Declares or executes a distinct() operation.
+ *
+ * Passing a `callback` executes the query.
+ *
+ * ####Example
+ *
+ *     distinct(criteria, field, fn)
+ *     distinct(criteria, field)
+ *     distinct(field, fn)
+ *     distinct(field)
+ *     distinct(fn)
+ *     distinct()
+ *
+ * @param {Object|Query} [criteria]
+ * @param {String} [field]
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @see mongodb http://www.mongodb.org/display/DOCS/Aggregation#Aggregation-Distinct
+ * @api public
+ */
+
+Query.prototype.distinct = function(criteria, field, callback) {
+  this.op = 'distinct';
+  this._validate();
+
+  if (!callback) {
+    switch (typeof field) {
+      case 'function':
+        callback = field;
+        if ('string' == typeof criteria) {
+          field = criteria;
+          criteria = undefined;
+        }
+        break;
+      case 'undefined':
+      case 'string':
+        break;
+      default:
+        throw new TypeError('Invalid `field` argument. Must be string or function');
+    }
+
+    switch (typeof criteria) {
+      case 'function':
+        callback = criteria;
+        criteria = field = undefined;
+        break;
+      case 'string':
+        field = criteria;
+        criteria = undefined;
+        break;
+    }
+  }
+
+  if ('string' == typeof field) {
+    this._distinct = field;
+  }
+
+  if (Query.canMerge(criteria)) {
+    this.merge(criteria);
+  }
+
+  if (!callback) {
+    return this;
+  }
+
+  if (!this._distinct) {
+    throw new Error('No value for `distinct` has been declared');
+  }
+
+  var conds = this._conditions,
+      options = this._optionsForExec();
+
+  debug('distinct', this._collection.collectionName, conds, options);
+  callback = this._wrapCallback('distinct', callback, {
+    conditions: conds,
+    options: options
+  });
+
+  this._collection.distinct(this._distinct, conds, options, utils.tick(callback));
+
+  return this;
+};
+
+/**
+ * Declare and/or execute this query as an update() operation. By default,
+ * `update()` only modifies the _first_ document that matches `criteria`.
+ *
+ * _All paths passed that are not $atomic operations will become $set ops._
+ *
+ * ####Example
+ *
+ *     mquery({ _id: id }).update({ title: 'words' }, ...)
+ *
+ * becomes
+ *
+ *     collection.update({ _id: id }, { $set: { title: 'words' }}, ...)
+ *
+ * ####Note
+ *
+ * Passing an empty object `{}` as the doc will result in a no-op unless the `overwrite` option is passed. Without the `overwrite` option set, the update operation will be ignored and the callback executed without sending the command to MongoDB so as to prevent accidently overwritting documents in the collection.
+ *
+ * ####Note
+ *
+ * The operation is only executed when a callback is passed. To force execution without a callback (which would be an unsafe write), we must first call update() and then execute it by using the `exec()` method.
+ *
+ *     var q = mquery(collection).where({ _id: id });
+ *     q.update({ $set: { name: 'bob' }}).update(); // not executed
+ *
+ *     var q = mquery(collection).where({ _id: id });
+ *     q.update({ $set: { name: 'bob' }}).exec(); // executed as unsafe
+ *
+ *     // keys that are not $atomic ops become $set.
+ *     // this executes the same command as the previous example.
+ *     q.update({ name: 'bob' }).where({ _id: id }).exec();
+ *
+ *     var q = mquery(collection).update(); // not executed
+ *
+ *     // overwriting with empty docs
+ *     var q.where({ _id: id }).setOptions({ overwrite: true })
+ *     q.update({ }, callback); // executes
+ *
+ *     // multi update with overwrite to empty doc
+ *     var q = mquery(collection).where({ _id: id });
+ *     q.setOptions({ multi: true, overwrite: true })
+ *     q.update({ });
+ *     q.update(callback); // executed
+ *
+ *     // multi updates
+ *     mquery()
+ *       .collection(coll)
+ *       .update({ name: /^match/ }, { $set: { arr: [] }}, { multi: true }, callback)
+ *     // more multi updates
+ *     mquery({ })
+ *       .collection(coll)
+ *       .setOptions({ multi: true })
+ *       .update({ $set: { arr: [] }}, callback)
+ *
+ *     // single update by default
+ *     mquery({ email: 'address@example.com' })
+ *      .collection(coll)
+ *      .update({ $inc: { counter: 1 }}, callback)
+ *
+ *     // summary
+ *     update(criteria, doc, opts, cb) // executes
+ *     update(criteria, doc, opts)
+ *     update(criteria, doc, cb) // executes
+ *     update(criteria, doc)
+ *     update(doc, cb) // executes
+ *     update(doc)
+ *     update(cb) // executes
+ *     update(true) // executes (unsafe write)
+ *     update()
+ *
+ * @param {Object} [criteria]
+ * @param {Object} [doc] the update command
+ * @param {Object} [options]
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.update = function update(criteria, doc, options, callback) {
+  var force;
+
+  switch (arguments.length) {
+    case 3:
+      if ('function' == typeof options) {
+        callback = options;
+        options = undefined;
+      }
+      break;
+    case 2:
+      if ('function' == typeof doc) {
+        callback = doc;
+        doc = criteria;
+        criteria = undefined;
+      }
+      break;
+    case 1:
+      switch (typeof criteria) {
+        case 'function':
+          callback = criteria;
+          criteria = options = doc = undefined;
+          break;
+        case 'boolean':
+          // execution with no callback (unsafe write)
+          force = criteria;
+          criteria = undefined;
+          break;
+        default:
+          doc = criteria;
+          criteria = options = undefined;
+          break;
+      }
+  }
+
+  return _update(this, 'update', criteria, doc, options, force, callback);
+};
+
+/**
+ * Declare and/or execute this query as an `updateMany()` operation. Identical
+ * to `update()` except `updateMany()` will update _all_ documents that match
+ * `criteria`, rather than just the first one.
+ *
+ * _All paths passed that are not $atomic operations will become $set ops._
+ *
+ * ####Example
+ *
+ *     // Update every document whose `title` contains 'test'
+ *     mquery().updateMany({ title: /test/ }, { year: 2017 })
+ *
+ * @param {Object} [criteria]
+ * @param {Object} [doc] the update command
+ * @param {Object} [options]
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.updateMany = function updateMany(criteria, doc, options, callback) {
+  var force;
+
+  switch (arguments.length) {
+    case 3:
+      if ('function' == typeof options) {
+        callback = options;
+        options = undefined;
+      }
+      break;
+    case 2:
+      if ('function' == typeof doc) {
+        callback = doc;
+        doc = criteria;
+        criteria = undefined;
+      }
+      break;
+    case 1:
+      switch (typeof criteria) {
+        case 'function':
+          callback = criteria;
+          criteria = options = doc = undefined;
+          break;
+        case 'boolean':
+          // execution with no callback (unsafe write)
+          force = criteria;
+          criteria = undefined;
+          break;
+        default:
+          doc = criteria;
+          criteria = options = undefined;
+          break;
+      }
+  }
+
+  return _update(this, 'updateMany', criteria, doc, options, force, callback);
+};
+
+/**
+ * Declare and/or execute this query as an `updateOne()` operation. Identical
+ * to `update()` except `updateOne()` will _always_ update just one document,
+ * regardless of the `multi` option.
+ *
+ * _All paths passed that are not $atomic operations will become $set ops._
+ *
+ * ####Example
+ *
+ *     // Update the first document whose `title` contains 'test'
+ *     mquery().updateMany({ title: /test/ }, { year: 2017 })
+ *
+ * @param {Object} [criteria]
+ * @param {Object} [doc] the update command
+ * @param {Object} [options]
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.updateOne = function updateOne(criteria, doc, options, callback) {
+  var force;
+
+  switch (arguments.length) {
+    case 3:
+      if ('function' == typeof options) {
+        callback = options;
+        options = undefined;
+      }
+      break;
+    case 2:
+      if ('function' == typeof doc) {
+        callback = doc;
+        doc = criteria;
+        criteria = undefined;
+      }
+      break;
+    case 1:
+      switch (typeof criteria) {
+        case 'function':
+          callback = criteria;
+          criteria = options = doc = undefined;
+          break;
+        case 'boolean':
+          // execution with no callback (unsafe write)
+          force = criteria;
+          criteria = undefined;
+          break;
+        default:
+          doc = criteria;
+          criteria = options = undefined;
+          break;
+      }
+  }
+
+  return _update(this, 'updateOne', criteria, doc, options, force, callback);
+};
+
+/**
+ * Declare and/or execute this query as an `replaceOne()` operation. Similar
+ * to `updateOne()`, except `replaceOne()` is not allowed to use atomic
+ * modifiers (`$set`, `$push`, etc.). Calling `replaceOne()` will always
+ * replace the existing doc.
+ *
+ * ####Example
+ *
+ *     // Replace the document with `_id` 1 with `{ _id: 1, year: 2017 }`
+ *     mquery().replaceOne({ _id: 1 }, { year: 2017 })
+ *
+ * @param {Object} [criteria]
+ * @param {Object} [doc] the update command
+ * @param {Object} [options]
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.replaceOne = function replaceOne(criteria, doc, options, callback) {
+  var force;
+
+  switch (arguments.length) {
+    case 3:
+      if ('function' == typeof options) {
+        callback = options;
+        options = undefined;
+      }
+      break;
+    case 2:
+      if ('function' == typeof doc) {
+        callback = doc;
+        doc = criteria;
+        criteria = undefined;
+      }
+      break;
+    case 1:
+      switch (typeof criteria) {
+        case 'function':
+          callback = criteria;
+          criteria = options = doc = undefined;
+          break;
+        case 'boolean':
+          // execution with no callback (unsafe write)
+          force = criteria;
+          criteria = undefined;
+          break;
+        default:
+          doc = criteria;
+          criteria = options = undefined;
+          break;
+      }
+  }
+
+  this.setOptions({ overwrite: true });
+  return _update(this, 'replaceOne', criteria, doc, options, force, callback);
+};
+
+
+/*!
+ * Internal helper for update, updateMany, updateOne
+ */
+
+function _update(query, op, criteria, doc, options, force, callback) {
+  query.op = op;
+
+  if (Query.canMerge(criteria)) {
+    query.merge(criteria);
+  }
+
+  if (doc) {
+    query._mergeUpdate(doc);
+  }
+
+  if (utils.isObject(options)) {
+    // { overwrite: true }
+    query.setOptions(options);
+  }
+
+  // we are done if we don't have callback and they are
+  // not forcing an unsafe write.
+  if (!(force || callback)) {
+    return query;
+  }
+
+  if (!query._update ||
+      !query.options.overwrite && 0 === utils.keys(query._update).length) {
+    callback && utils.soon(callback.bind(null, null, 0));
+    return query;
+  }
+
+  options = query._optionsForExec();
+  if (!callback) options.safe = false;
+
+  criteria = query._conditions;
+  doc = query._updateForExec();
+
+  debug('update', query._collection.collectionName, criteria, doc, options);
+  callback = query._wrapCallback(op, callback, {
+    conditions: criteria,
+    doc: doc,
+    options: options
+  });
+
+  query._collection[op](criteria, doc, options, utils.tick(callback));
+
+  return query;
+}
+
+/**
+ * Declare and/or execute this query as a remove() operation.
+ *
+ * ####Example
+ *
+ *     mquery(collection).remove({ artist: 'Anne Murray' }, callback)
+ *
+ * ####Note
+ *
+ * The operation is only executed when a callback is passed. To force execution without a callback (which would be an unsafe write), we must first call remove() and then execute it by using the `exec()` method.
+ *
+ *     // not executed
+ *     var query = mquery(collection).remove({ name: 'Anne Murray' })
+ *
+ *     // executed
+ *     mquery(collection).remove({ name: 'Anne Murray' }, callback)
+ *     mquery(collection).remove({ name: 'Anne Murray' }).remove(callback)
+ *
+ *     // executed without a callback (unsafe write)
+ *     query.exec()
+ *
+ *     // summary
+ *     query.remove(conds, fn); // executes
+ *     query.remove(conds)
+ *     query.remove(fn) // executes
+ *     query.remove()
+ *
+ * @param {Object|Query} [criteria] mongodb selector
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.remove = function(criteria, callback) {
+  this.op = 'remove';
+  var force;
+
+  if ('function' === typeof criteria) {
+    callback = criteria;
+    criteria = undefined;
+  } else if (Query.canMerge(criteria)) {
+    this.merge(criteria);
+  } else if (true === criteria) {
+    force = criteria;
+    criteria = undefined;
+  }
+
+  if (!(force || callback))
+    return this;
+
+  var options = this._optionsForExec();
+  if (!callback) options.safe = false;
+
+  var conds = this._conditions;
+
+  debug('remove', this._collection.collectionName, conds, options);
+  callback = this._wrapCallback('remove', callback, {
+    conditions: conds,
+    options: options
+  });
+
+  this._collection.remove(conds, options, utils.tick(callback));
+
+  return this;
+};
+
+/**
+ * Declare and/or execute this query as a `deleteOne()` operation. Behaves like
+ * `remove()`, except for ignores the `justOne` option and always deletes at
+ * most one document.
+ *
+ * ####Example
+ *
+ *     mquery(collection).deleteOne({ artist: 'Anne Murray' }, callback)
+ *
+ * @param {Object|Query} [criteria] mongodb selector
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.deleteOne = function(criteria, callback) {
+  this.op = 'deleteOne';
+  var force;
+
+  if ('function' === typeof criteria) {
+    callback = criteria;
+    criteria = undefined;
+  } else if (Query.canMerge(criteria)) {
+    this.merge(criteria);
+  } else if (true === criteria) {
+    force = criteria;
+    criteria = undefined;
+  }
+
+  if (!(force || callback))
+    return this;
+
+  var options = this._optionsForExec();
+  if (!callback) options.safe = false;
+  delete options.justOne;
+
+  var conds = this._conditions;
+
+  debug('deleteOne', this._collection.collectionName, conds, options);
+  callback = this._wrapCallback('deleteOne', callback, {
+    conditions: conds,
+    options: options
+  });
+
+  this._collection.deleteOne(conds, options, utils.tick(callback));
+
+  return this;
+};
+
+/**
+ * Declare and/or execute this query as a `deleteMany()` operation. Behaves like
+ * `remove()`, except for ignores the `justOne` option and always deletes
+ * _every_ document that matches `criteria`.
+ *
+ * ####Example
+ *
+ *     mquery(collection).deleteMany({ artist: 'Anne Murray' }, callback)
+ *
+ * @param {Object|Query} [criteria] mongodb selector
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.deleteMany = function(criteria, callback) {
+  this.op = 'deleteMany';
+  var force;
+
+  if ('function' === typeof criteria) {
+    callback = criteria;
+    criteria = undefined;
+  } else if (Query.canMerge(criteria)) {
+    this.merge(criteria);
+  } else if (true === criteria) {
+    force = criteria;
+    criteria = undefined;
+  }
+
+  if (!(force || callback))
+    return this;
+
+  var options = this._optionsForExec();
+  if (!callback) options.safe = false;
+  delete options.justOne;
+
+  var conds = this._conditions;
+
+  debug('deleteOne', this._collection.collectionName, conds, options);
+  callback = this._wrapCallback('deleteOne', callback, {
+    conditions: conds,
+    options: options
+  });
+
+  this._collection.deleteMany(conds, options, utils.tick(callback));
+
+  return this;
+};
+
+/**
+ * Issues a mongodb [findAndModify](http://www.mongodb.org/display/DOCS/findAndModify+Command) update command.
+ *
+ * Finds a matching document, updates it according to the `update` arg, passing any `options`, and returns the found document (if any) to the callback. The query executes immediately if `callback` is passed.
+ *
+ * ####Available options
+ *
+ * - `new`: bool - true to return the modified document rather than the original. defaults to true
+ * - `upsert`: bool - creates the object if it doesn't exist. defaults to false.
+ * - `sort`: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
+ *
+ * ####Examples
+ *
+ *     query.findOneAndUpdate(conditions, update, options, callback) // executes
+ *     query.findOneAndUpdate(conditions, update, options)  // returns Query
+ *     query.findOneAndUpdate(conditions, update, callback) // executes
+ *     query.findOneAndUpdate(conditions, update)           // returns Query
+ *     query.findOneAndUpdate(update, callback)             // returns Query
+ *     query.findOneAndUpdate(update)                       // returns Query
+ *     query.findOneAndUpdate(callback)                     // executes
+ *     query.findOneAndUpdate()                             // returns Query
+ *
+ * @param {Object|Query} [query]
+ * @param {Object} [doc]
+ * @param {Object} [options]
+ * @param {Function} [callback]
+ * @see mongodb http://www.mongodb.org/display/DOCS/findAndModify+Command
+ * @return {Query} this
+ * @api public
+ */
+
+Query.prototype.findOneAndUpdate = function(criteria, doc, options, callback) {
+  this.op = 'findOneAndUpdate';
+  this._validate();
+
+  switch (arguments.length) {
+    case 3:
+      if ('function' == typeof options) {
+        callback = options;
+        options = {};
+      }
+      break;
+    case 2:
+      if ('function' == typeof doc) {
+        callback = doc;
+        doc = criteria;
+        criteria = undefined;
+      }
+      options = undefined;
+      break;
+    case 1:
+      if ('function' == typeof criteria) {
+        callback = criteria;
+        criteria = options = doc = undefined;
+      } else {
+        doc = criteria;
+        criteria = options = undefined;
+      }
+  }
+
+  if (Query.canMerge(criteria)) {
+    this.merge(criteria);
+  }
+
+  // apply doc
+  if (doc) {
+    this._mergeUpdate(doc);
+  }
+
+  options && this.setOptions(options);
+
+  if (!callback) return this;
+  return this._findAndModify('update', callback);
+};
+
+/**
+ * Issues a mongodb [findAndModify](http://www.mongodb.org/display/DOCS/findAndModify+Command) remove command.
+ *
+ * Finds a matching document, removes it, passing the found document (if any) to the callback. Executes immediately if `callback` is passed.
+ *
+ * ####Available options
+ *
+ * - `sort`: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
+ *
+ * ####Examples
+ *
+ *     A.where().findOneAndRemove(conditions, options, callback) // executes
+ *     A.where().findOneAndRemove(conditions, options)  // return Query
+ *     A.where().findOneAndRemove(conditions, callback) // executes
+ *     A.where().findOneAndRemove(conditions) // returns Query
+ *     A.where().findOneAndRemove(callback)   // executes
+ *     A.where().findOneAndRemove()           // returns Query
+ *     A.where().findOneAndDelete()           // alias of .findOneAndRemove()
+ *
+ * @param {Object} [conditions]
+ * @param {Object} [options]
+ * @param {Function} [callback]
+ * @return {Query} this
+ * @see mongodb http://www.mongodb.org/display/DOCS/findAndModify+Command
+ * @api public
+ */
+
+Query.prototype.findOneAndRemove = Query.prototype.findOneAndDelete = function(conditions, options, callback) {
+  this.op = 'findOneAndRemove';
+  this._validate();
+
+  if ('function' == typeof options) {
+    callback = options;
+    options = undefined;
+  } else if ('function' == typeof conditions) {
+    callback = conditions;
+    conditions = undefined;
+  }
+
+  // apply conditions
+  if (Query.canMerge(conditions)) {
+    this.merge(conditions);
+  }
+
+  // apply options
+  options && this.setOptions(options);
+
+  if (!callback) return this;
+
+  return this._findAndModify('remove', callback);
+};
+
+/**
+ * _findAndModify
+ *
+ * @param {String} type - either "remove" or "update"
+ * @param {Function} callback
+ * @api private
+ */
+
+Query.prototype._findAndModify = function(type, callback) {
+  assert.equal('function', typeof callback);
+
+  var options = this._optionsForExec();
+  var fields;
+  var doc;
+
+  if ('remove' == type) {
+    options.remove = true;
+  } else {
+    if (!('new' in options)) options.new = true;
+    if (!('upsert' in options)) options.upsert = false;
+
+    doc = this._updateForExec();
+    if (!doc) {
+      if (options.upsert) {
+        // still need to do the upsert to empty doc
+        doc = { $set: {} };
+      } else {
+        return this.findOne(callback);
+      }
+    }
+  }
+
+  fields = this._fieldsForExec();
+  if (fields != null) {
+    if (this.$useProjection) {
+      options.projection = this._fieldsForExec();
+    } else {
+      options.fields = this._fieldsForExec();
+    }
+  }
+
+  var conds = this._conditions;
+
+  debug('findAndModify', this._collection.collectionName, conds, doc, options);
+  callback = this._wrapCallback('findAndModify', callback, {
+    conditions: conds,
+    doc: doc,
+    options: options
+  });
+
+  this._collection.findAndModify(conds, doc, options, utils.tick(callback));
+
+  return this;
+};
+
+/**
+ * Wrap callback to add tracing
+ *
+ * @param {Function} callback
+ * @param {Object} [queryInfo]
+ * @api private
+ */
+Query.prototype._wrapCallback = function(method, callback, queryInfo) {
+  var traceFunction = this._traceFunction || Query.traceFunction;
+
+  if (traceFunction) {
+    queryInfo.collectionName = this._collection.collectionName;
+
+    var traceCallback = traceFunction &&
+      traceFunction.call(null, method, queryInfo, this);
+
+    var startTime = new Date().getTime();
+
+    return function wrapperCallback(err, result) {
+      if (traceCallback) {
+        var millis = new Date().getTime() - startTime;
+        traceCallback.call(null, err, result, millis);
+      }
+
+      if (callback) {
+        callback.apply(null, arguments);
+      }
+    };
+  }
+
+  return callback;
+};
+
+/**
+ * Add trace function that gets called when the query is executed.
+ * The function will be called with (method, queryInfo, query) and
+ * should return a callback function which will be called
+ * with (err, result, millis) when the query is complete.
+ *
+ * queryInfo is an object containing: {
+ *   collectionName: <name of the collection>,
+ *   conditions: <query criteria>,
+ *   options: <comment, fields, readPreference, etc>,
+ *   doc: [document to update, if applicable]
+ * }
+ *
+ * NOTE: Does not trace stream queries.
+ *
+ * @param {Function} traceFunction
+ * @return {Query} this
+ * @api public
+ */
+Query.prototype.setTraceFunction = function(traceFunction) {
+  this._traceFunction = traceFunction;
+  return this;
+};
+
+/**
+ * Executes the query
+ *
+ * ####Examples
+ *
+ *     query.exec();
+ *     query.exec(callback);
+ *     query.exec('update');
+ *     query.exec('find', callback);
+ *
+ * @param {String|Function} [operation]
+ * @param {Function} [callback]
+ * @api public
+ */
+
+Query.prototype.exec = function exec(op, callback) {
+  switch (typeof op) {
+    case 'function':
+      callback = op;
+      op = null;
+      break;
+    case 'string':
+      this.op = op;
+      break;
+  }
+
+  assert.ok(this.op, 'Missing query type: (find, update, etc)');
+
+  if ('update' == this.op || 'remove' == this.op) {
+    callback || (callback = true);
+  }
+
+  var _this = this;
+
+  if ('function' == typeof callback) {
+    this[this.op](callback);
+  } else {
+    return new Query.Promise(function(success, error) {
+      _this[_this.op](function(err, val) {
+        if (err) error(err);
+        else success(val);
+        success = error = null;
+      });
+    });
+  }
+};
+
+/**
+ * Returns a thunk which when called runs this.exec()
+ *
+ * The thunk receives a callback function which will be
+ * passed to `this.exec()`
+ *
+ * @return {Function}
+ * @api public
+ */
+
+Query.prototype.thunk = function() {
+  var _this = this;
+  return function(cb) {
+    _this.exec(cb);
+  };
+};
+
+/**
+ * Executes the query returning a `Promise` which will be
+ * resolved with either the doc(s) or rejected with the error.
+ *
+ * @param {Function} [resolve]
+ * @param {Function} [reject]
+ * @return {Promise}
+ * @api public
+ */
+
+Query.prototype.then = function(resolve, reject) {
+  var _this = this;
+  var promise = new Query.Promise(function(success, error) {
+    _this.exec(function(err, val) {
+      if (err) error(err);
+      else success(val);
+      success = error = null;
+    });
+  });
+  return promise.then(resolve, reject);
+};
+
+/**
+ * Returns a stream for the given find query.
+ *
+ * @throws Error if operation is not a find
+ * @returns {Stream} Node 0.8 style
+ */
+
+Query.prototype.stream = function(streamOptions) {
+  if ('find' != this.op)
+    throw new Error('stream() is only available for find');
+
+  var conds = this._conditions;
+
+  var options = this._optionsForExec();
+  if (this.$useProjection) {
+    options.projection = this._fieldsForExec();
+  } else {
+    options.fields = this._fieldsForExec();
+  }
+
+  debug('stream', this._collection.collectionName, conds, options, streamOptions);
+
+  return this._collection.findStream(conds, options, streamOptions);
+};
+
+/**
+ * Determines if field selection has been made.
+ *
+ * @return {Boolean}
+ * @api public
+ */
+
+Query.prototype.selected = function selected() {
+  return !!(this._fields && Object.keys(this._fields).length > 0);
+};
+
+/**
+ * Determines if inclusive field selection has been made.
+ *
+ *     query.selectedInclusively() // false
+ *     query.select('name')
+ *     query.selectedInclusively() // true
+ *     query.selectedExlusively() // false
+ *
+ * @returns {Boolean}
+ */
+
+Query.prototype.selectedInclusively = function selectedInclusively() {
+  if (!this._fields) return false;
+
+  var keys = Object.keys(this._fields);
+  if (0 === keys.length) return false;
+
+  for (var i = 0; i < keys.length; ++i) {
+    var key = keys[i];
+    if (0 === this._fields[key]) return false;
+    if (this._fields[key] &&
+        typeof this._fields[key] === 'object' &&
+        this._fields[key].$meta) {
+      return false;
+    }
+  }
+
+  return true;
+};
+
+/**
+ * Determines if exclusive field selection has been made.
+ *
+ *     query.selectedExlusively() // false
+ *     query.select('-name')
+ *     query.selectedExlusively() // true
+ *     query.selectedInclusively() // false
+ *
+ * @returns {Boolean}
+ */
+
+Query.prototype.selectedExclusively = function selectedExclusively() {
+  if (!this._fields) return false;
+
+  var keys = Object.keys(this._fields);
+  if (0 === keys.length) return false;
+
+  for (var i = 0; i < keys.length; ++i) {
+    var key = keys[i];
+    if (0 === this._fields[key]) return true;
+  }
+
+  return false;
+};
+
+/**
+ * Merges `doc` with the current update object.
+ *
+ * @param {Object} doc
+ */
+
+Query.prototype._mergeUpdate = function(doc) {
+  if (!this._update) this._update = {};
+  if (doc instanceof Query) {
+    if (doc._update) {
+      utils.mergeClone(this._update, doc._update);
+    }
+  } else {
+    utils.mergeClone(this._update, doc);
+  }
+};
+
+/**
+ * Returns default options.
+ *
+ * @return {Object}
+ * @api private
+ */
+
+Query.prototype._optionsForExec = function() {
+  var options = utils.clone(this.options);
+  return options;
+};
+
+/**
+ * Returns fields selection for this query.
+ *
+ * @return {Object}
+ * @api private
+ */
+
+Query.prototype._fieldsForExec = function() {
+  return utils.clone(this._fields);
+};
+
+/**
+ * Return an update document with corrected $set operations.
+ *
+ * @api private
+ */
+
+Query.prototype._updateForExec = function() {
+  var update = utils.clone(this._update),
+      ops = utils.keys(update),
+      i = ops.length,
+      ret = {};
+
+  while (i--) {
+    var op = ops[i];
+
+    if (this.options.overwrite) {
+      ret[op] = update[op];
+      continue;
+    }
+
+    if ('$' !== op[0]) {
+      // fix up $set sugar
+      if (!ret.$set) {
+        if (update.$set) {
+          ret.$set = update.$set;
+        } else {
+          ret.$set = {};
+        }
+      }
+      ret.$set[op] = update[op];
+      ops.splice(i, 1);
+      if (!~ops.indexOf('$set')) ops.push('$set');
+    } else if ('$set' === op) {
+      if (!ret.$set) {
+        ret[op] = update[op];
+      }
+    } else {
+      ret[op] = update[op];
+    }
+  }
+
+  this._compiledUpdate = ret;
+  return ret;
+};
+
+/**
+ * Make sure _path is set.
+ *
+ * @parmam {String} method
+ */
+
+Query.prototype._ensurePath = function(method) {
+  if (!this._path) {
+    var msg = method + '() must be used after where() '
+                     + 'when called with these arguments';
+    throw new Error(msg);
+  }
+};
+
+/*!
+ * Permissions
+ */
+
+Query.permissions = require('./permissions');
+
+Query._isPermitted = function(a, b) {
+  var denied = Query.permissions[b];
+  if (!denied) return true;
+  return true !== denied[a];
+};
+
+Query.prototype._validate = function(action) {
+  var fail;
+  var validator;
+
+  if (undefined === action) {
+
+    validator = Query.permissions[this.op];
+    if ('function' != typeof validator) return true;
+
+    fail = validator(this);
+
+  } else if (!Query._isPermitted(action, this.op)) {
+    fail = action;
+  }
+
+  if (fail) {
+    throw new Error(fail + ' cannot be used with ' + this.op);
+  }
+};
+
+/**
+ * Determines if `conds` can be merged using `mquery().merge()`
+ *
+ * @param {Object} conds
+ * @return {Boolean}
+ */
+
+Query.canMerge = function(conds) {
+  return conds instanceof Query || utils.isObject(conds);
+};
+
+/**
+ * Set a trace function that will get called whenever a
+ * query is executed.
+ *
+ * See `setTraceFunction()` for details.
+ *
+ * @param {Object} conds
+ * @return {Boolean}
+ */
+Query.setGlobalTraceFunction = function(traceFunction) {
+  Query.traceFunction = traceFunction;
+};
+
+/*!
+ * Exports.
+ */
+
+Query.utils = utils;
+Query.env = require('./env');
+Query.Collection = require('./collection');
+Query.BaseCollection = require('./collection/collection');
+Query.Promise = require('bluebird');
+module.exports = exports = Query;
+
+// TODO
+// test utils