mongodb mapreduce中的条件

Question

我如何在mongos group功能中指定mongos mapreduce中的条件.

我的数据就像

{lid:1000, age:23}, {lid:3000, age:23}, {lid:1000, age:24}. 

我想只发出值为1000的盖子emit(this.lid, this.age).但这会发出所有价值.我想在这里有一个条件.地图中是否有任何减少方法？我试图在reduce函数中使用if条件进行过滤,但它不起作用

Answer 1

您可以在query参数中执行此操作.从文档页面:http://www.mongodb.org/display/DOCS/MapReduce#MapReduce-Overview

db.runCommand(
 { mapreduce : <collection>,
   map : <mapfunction>,
   reduce : <reducefunction>

   --> [, query : <query filter object>] <--

   [, sort : <sorts the input objects using this key. Useful for optimization, like sorting by the emit key for fewer reduces>]
   [, limit : <number of objects to return from collection>]
   [, out : <see output options below>]
   [, keeptemp: <true|false>]
   [, finalize : <finalizefunction>]
   [, scope : <object where fields go into javascript global scope >]
   [, verbose : true]
 }
);