aggregation framework

1. Aggregation Frameworkusing the aggregation framework to transform and combine documents in a collection, you can create a pipeline (pipeline) with multiple artifacts to process a series of documents. These artifacts include filtering (filtering),

Group of aggregation operationsGrammar:Db.collection.group ({Key:{key1:1,key2:1},cond:{},Reduce:function (Curr,result) {},initial:{},Finalize:function () {}})Key: Group FieldCond: Query criteriaReduce: aggregate functionInitial:

Today, I saw someone write a custom aggregation function, so mindedly want to understand, on the Internet to find information. Introduction to custom aggregate function custom aggregation function interfacesOracle provides a number of pre-defined

in the two previous articles the basic aggregation function of data aggregation in MongoDB count, distinct, group > and the MapReduce of data aggregation in MongoDB >, we've provided two implementations for data aggregation, and today, in this

First, IntroductionMongoDB's aggregation framework, which is used primarily to transform and combine the documents in a collection to make use of the data for analysis.The basic idea of the aggregation framework is:Multiple artifacts are used to

The previous blog post describes how the collation collations is manipulated and set up. Incidentally, some of the aggregation aggregation are set up in this way. This article continues to describe aggregation operations.The operation of the

Aggregation IntroductionThe aggregation operation is the operation that comes out of the data record and returns the computed result. MongoDB provides a rich aggregation operation to detect and execute calculations on datasets. Data aggregation

PrefaceThere are 3 days to end in 2014, and this month's plan has been completed in addition to the summary of MongoDB's other plans. Recently, lazy research on MongoDB has been suspended for a long time. In the last three days, the study of MongoDB

Zheng @ playpoly SD 20081108 The following is my family's statement for your reference only. Introduction Google, Baidu, Yahoo, and new launch are all testing more types of onebox. For example, if you search for "population of China" in Google,

Aggregate is the more important of the many tools that MongoDB provides, similar to the one in SQL statements GROUP BY . The aggregation tool allows developers to manipulate data in the database directly using MongoDB native commands, and aggregates