MongoDB中的计数和汇总 [英] Count and Aggregate in MongoDB

问题描述

我有mongodb集合，其结构如下:-

I have mongodb collection whose structure is as follows :-

{
"_id" : "mongo",
"log" : [
    {
        "ts" : ISODate("2011-02-10T01:20:49Z"),
        "visitorId" : "25850661"
    },
    {
        "ts" : ISODate("2014-11-01T14:35:05Z"),
        "visitorId" : NumberLong(278571823)
    },
    {
        "ts" : ISODate("2014-11-01T14:37:56Z"),
        "visitorId" : NumberLong(0)
    },
    {
        "ts" : ISODate("2014-11-04T06:23:48Z"),
        "visitorId" : NumberLong(225200092)
    },
    {
        "ts" : ISODate("2014-11-04T06:25:44Z"),
        "visitorId" : NumberLong(225200092)
    }
],
"uts" : ISODate("2014-11-04T06:25:43.740Z")
}

"mongo"是一个搜索词，"ts"表示在网站上搜索的时间戳.

"mongo" is a search term and "ts" indicates the timestamp when it was searched on website.

"uts"表示上次搜索.

"uts" indicates the last time it was searched.

因此在我们的网站上搜索了5个搜索词"mongo".

So search term "mongo" was searched 5 times on our website.

我需要获得过去3个月搜索量最高的50个项目.

I need to get top 50 most searched items in past 3 months.

我不是mongodb聚合方面的专家，但是我正在尝试类似的方法以至少获取过去3个月的数据:-

I am no expert in aggregation in mongodb, but i was trying something like this to atleast get data of past 3 months: -

db.collection.aggregate({$group:{_id:"$_id",count:{$sum:1}}},{$match:{"log.ts":{"$gte":new Date("2014-09-01")}}})

它给了我错误:-

exception: sharded pipeline failed on shard DSink9: { errmsg: \"exception: aggregation result exceeds maximum document size (16MB)\", code: 16389

有人可以帮助我吗?

更新

我能够写一些查询.但这给了我语法错误.

I was able to write some query. But it gives me syntax error.

db.collection.aggregate(
{$unwind:"$log"},
{$project:{log:"$log.ts"}},
{$match:{log:{"$gte" : new Date("2014-09-01"),"$lt" : new Date("2014-11-04")}}},
{$project:{_id:{val:{"$_id"}}}},
{$group:{_id:"$_id",sum:{$sum:1}}})

推荐答案

结果超出了最大文档大小，但这通常表明您做错了"，特别是考虑到您在两个日期之间在存储的数据中搜索"mongo"的示例术语:

You are exceeding a maximum document size in a result, but generally that is an indication that you are "doing it wrong", particularly given your example term of searching for "mongo" in your stored data between two dates:

db.collection.aggregate([
   // Always match first, it reduces the workload and can use an index here only.
   { "$match": { 
       "_id": "mongo" 
       "log.ts": {
           "$gte": new Date("2014-09-01"), "$lt": new Date("2014-11-04")
       }
   }},

   // Unwind the array to de-normalize as documents
   { "$unwind": "$log" },

   // Get the count within the range, so match first to "filter"
   { "$match": { 
       "log.ts": {
           "$gte": new Date("2014-09-01"), "$lt": new Date("2014-11-04")
       }
   }},

   // Group the count on `_id`
   { "$group": {
       "_id": "$_id",
       "count": { "$sum": 1 }
   }}
]);

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