统计

Aggregate([ops])

Aggregate constructor used for building aggregation pipelines.

参数:

[ops] 统计操作符或统计数组

参考:

MongoDB驱动器

例子:

new Aggregate();
new Aggregate({ $project: { a: 1, b: 1 } });
new Aggregate({ $project: { a: 1, b: 1 } }, { $skip: 5 });
new Aggregate([{ $project: { a: 1, b: 1 } }, { $skip: 5 }]);

Returned when calling Model.aggregate().

例子:

Model
  .aggregate({ $match: { age: { $gte: 21 }}})
  .unwind('tags')
  .exec(callback)

注意:

• The documents returned are plain javascript objects, not mongoose documents (since any shape of document can be returned).
• 需要 MongoDB >= 2.1

function Aggregate () {
  this._pipeline = [];
  this._model = undefined;
  this.options = undefined;

  if (1 === arguments.length && util.isArray(arguments[0])) {
    this.append.apply(this, arguments[0]);
  } else {
    this.append.apply(this, arguments);
  }
}

Aggregate#allowDiskUse(value, [tags])

为统计查询设置allowDiskUse选项 (忽略 < 2.6.0)

参数:

• value <Boolean>告诉服务器统计时可以用硬盘存储数据.
• [tags] <Array> 查询标签，可选

参考:

mongodb

例子:

Model.aggregate(..).allowDiskUse(true).exec(callback)

Aggregate#append(ops)

附加新的操作符到统计管道

参数:

• ops <Object> 附加的操作符

返回:

<Aggregate>

例子:

aggregate.append({ $project: { field: 1 }}, { $limit: 2 });
// or pass an array
var pipeline = [{ $match: { daw: 'Logic Audio X' }} ];
aggregate.append(pipeline);

Aggregate#cursor(options)

为统计查询设置游标可选 选项 (忽略 < 2.6.0). 注意以下不同的语法: .exec() 返回游标对象且回调函数非必须

参数:

options <Object> 设置游标批量大小

参考:

mongodb

例子:

var cursor = Model.aggregate(..).cursor({ batchSize: 1000 }).exec();
cursor.each(function(error, doc) {
  // use doc
});

Aggregate#exec([callback])

在当前绑定模型里执行统计管道

参数:

[callback] <Function>

返回:

<Promise>

参考:

Promise

例子:

aggregate.exec(callback);

// Because a promise is returned, the `callback` is optional.
var promise = aggregate.exec();
promise.then(..);

Aggregate#explain(callback)

附带解析执行统计

参数:

callback <Function>

返回:

<Promise>

例子:

Model.aggregate(..).explain(callback)

Aggregate#group(arg)

附加 $group 操作符到统计管道

参数:

arg <Object> $group 操作符内容

返回:

<Aggregate>

参考:

$group

例子:

aggregate.group({ _id: "$department" });

Aggregate#limit(num)

附加 $limit 操作符到统计管道

参数:

num <Number> 传给下一步的记录最大数

返回:

<Aggregate>

参考:

$limit

例子:

aggregate.limit(10);

Aggregate#match(arg)

附加 $match 操作符到统计管道

参数:

arg <Object> $match 操作符内容

返回:

<Aggregate>

参考:

$match

例子:

aggregate.match({ department: { $in: [ "sales", "engineering" } } });

Aggregate#model(model)

绑定统计到模型.

参数:

model <Model> 要绑定统计的模型

返回:

<Aggregate>

Aggregate#near(parameters)

附加 $geoNear 操作符到统计管道

参数:

parameters <Object>

返回:

<Aggregate>

参考:

$geoNear

注意:

必须在管道里用为第一个操作符

例子:

aggregate.near({
  near: [40.724, -73.997],
  distanceField: "dist.calculated", // required
  maxDistance: 0.008,
  query: { type: "public" },
  includeLocs: "dist.location",
  uniqueDocs: true,
  num: 5
});

Aggregate#project(arg)

附加 $project 操作符到统计管道

参数:

arg <Object, String> 字段说明

返回:

<Aggregate>

参考:

projection

Mongoose query selection syntax is also supported.

例子:

// include a, include b, exclude _id
aggregate.project("a b -_id");

// or you may use object notation, useful when
// you have keys already prefixed with a "-"
aggregate.project({a: 1, b: 1, _id: 0});

// reshaping documents
aggregate.project({
    newField: '$b.nested'
  , plusTen: { $add: ['$val', 10]}
  , sub: {
       name: '$a'
    }
})

// etc
aggregate.project({ salary_k: { $divide: [ "$salary", 1000 ] } });

Aggregate#read(pref, [tags])

Sets the readPreference option for the aggregation query.

参数:

pref <String> one of the listed preference options or their aliases [tags] <Array> optional tags for this query

参考:

mongodb driver

例子:

Model.aggregate(..).read('primaryPreferred').exec(callback)

Aggregate#skip(num)

Appends a new $skip operator to this aggregate pipeline.

参数:

num <Number> number of records to skip before next stage

返回:

<Aggregate>

参考:

$skip

例子:

aggregate.skip(10);

Aggregate#sort(arg)

Appends a new $sort operator to this aggregate pipeline.

参数:

arg <Object, String>

返回:

<Aggregate> this

参考:

$sort

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.

例子:

// these are equivalent
aggregate.sort({ field: 'asc', test: -1 });
aggregate.sort('field -test');

Aggregate#unwind(fields)

Appends new custom $unwind operator(s) to this aggregate pipeline.

参数:

fields <String> the field(s) to unwind

返回:

<Aggregate>

参考:

$unwind

Note that the $unwind operator requires the path name to start with '$'. Mongoose will prepend '$' if the specified field doesn't start '$'.

例子:

aggregate.unwind("tags");
aggregate.unwind("a", "b", "c");