Mongodb聚合计数数组/集大小 [英] Mongodb Aggregation count array/set size

问题描述

这里是我的问题：

模型：

< abc，date：Time.now，status：1user_id：[id1，id2，
id4]}

{application：abc date：Date.yesterday，status：1，user_id：[
id1，id3，id5]}

{application：abc Time.yesterday-1，status：1，user_id：[
id1，id3，id5]}

需要计算一段时间内user_ids的唯一数。

预期结果：

{application：abc，status：1，unique_id_count：5}

聚合框架和计数mongodb外部的id。

{$ match：{application：abc}}，{$ unwind：$ users}，{$ group：
{_id：{status：$ status}，
users：{$ addToSet：$ users}}}

我的用户数组id非常大，所以我必须重复日期或者我将获得最大文档限制（16mb）。

我也可以$ group by

{year：{$ year：$ date}，month ：{$ month：$ date}，day：{
$ dayOfMonth：$ date}

我也得到文档大小限制。

是否可以计算mongodb中的设置大小？

解决方案

以下内容将返回每个应用程序的uniqueUsers数。这将通过使用mongodb的管道特性将组操作应用于组操作的结果。

  {$ match：{application ：abc}，
 {$ unwind：$ users}，
 {$ group：{_id：$ status，users：{$ addToSet：$ users}}} ，
 {$ unwind：$ users}，
 {$ group：{_id：$ _id，count：{$ sum：1}}} 
  {$ project：{id：$ _id，count：{$ size：$ uniqueUsers}}}  
 https://jira.mongodb.org/browse/SERVER-4899  
 
 
 
干杯
 
Here's my problem:

Model:

  
{ application: "abc", date: Time.now, status: "1" user_id: [ id1, id2,
  id4] }
  
  
{ application: "abc", date: Time.yesterday, status: "1", user_id: [
  id1, id3, id5] }
  
  
{ application: "abc", date: Time.yesterday-1, status: "1", user_id: [
  id1, id3, id5] }
I need to count the unique number of user_ids in a period of time.

Expected result:

  
{   application: "abc",   status: "1",   unique_id_count: 5 }
I'm currently using the aggregation framework and counting the ids outside mongodb.

  
{ $match: { application: "abc" } }, { $unwind: "$users" },  { $group:
  { _id: { status: "$status"}, 
             users: { $addToSet: "$users" } } }
My arrays of users ids are very large, so I have to iterate the dates or I'll get the maximum document limit (16mb).

I could also $group by

  
{ year: { $year: "$date" }, month: { $month: "$date" }, day: {
  $dayOfMonth: "$date" }
but I also get the document size limitation.

Is it possible to count the set size in mongodb?

thanks
解决方案
The following will return number of uniqueUsers per application. This will apply an group operation to a result of a group operation by using pipeline feature of mongodb.
{ $match: { application: "abc" } }, 
{ $unwind: "$users" }, 
{ $group: { _id: "$status", users: { $addToSet: "$users" } } }, 
{ $unwind:"$users" }, 
{ $group : {_id : "$_id", count : {$sum : 1} } }
Hopefully this will be done in an easier way in the following releases of mongo by a command which gives the size of an array under a projection. {$project: {id: "$_id", count: {$size: "$uniqueUsers"}}}
https://jira.mongodb.org/browse/SERVER-4899

Cheers

                        
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