MongoDB聚合分组取第一条记录的案例与实现方法

前言

今天开发同学向我们提了一个紧急的需求，从集合mt_resources_access_log中，根据字段refererDomain分组，取分组中最近一笔插入的数据，然后将这些符合条件的数据导入到集合mt_resources_access_log_new中。

接到这个需求，还是有些心虚的，原因有二，一是，业务需要，时间紧；二是，实现这个功能mongoDB聚合感觉有些复杂，聚合要走好多步。

数据记录格式如下：

记录1

{
 "_id" : ObjectId("5c1e23eaa66bf62c0c390afb"),
 "_class" : "C1",
 "resourceUrl" : "/static/js/p.js",
 "refererDomain" : "1234",
 "resourceType" : "static_resource",
 "ip" : "17.17.13.13",
 "createTime" : ISODate("2018-12-22T19:45:46.015+08:00"),
 "disabled" : 0
}

记录2

{
 "_id" : ObjectId("5c1e23eaa66bf62c0c390afb"),
 "_class" : "C1",
 "resourceUrl" : "/static/js/p.js",
 "refererDomain" : "1234",
 "resourceType" : "Dome_resource",
 "ip" : "17.17.13.14",
 "createTime" : ISODate("2018-12-21T19:45:46.015+08:00"),
 "disabled" : 0
}

记录3

{
 "_id" : ObjectId("5c1e23eaa66bf62c0c390afb"),
 "_class" : "C2",
 "resourceUrl" : "/static/js/p.js",
 "refererDomain" : "1235",
 "resourceType" : "static_resource",
 "ip" : "17.17.13.13",
 "createTime" : ISODate("2018-12-20T19:45:46.015+08:00"),
 "disabled" : 0
}
记录4

{
 "_id" : ObjectId("5c1e23eaa66bf62c0c390afb"),
 "_class" : "C2",
 "resourceUrl" : "/static/js/p.js",
 "refererDomain" : "1235",
 "resourceType" : "Dome_resource",
 "ip" : "17.17.13.13",
 "createTime" : ISODate("2018-12-20T19:45:46.015+08:00"),
 "disabled" : 0
}