在$ group的mongodb聚合框架中使用$ regex

问题描述

请考虑以下示例:

db.article.aggregate(
  { $group : {
      _id : "$author",
      docsPerAuthor : { $sum : 1 },
      viewsPerAuthor : { $sum : "$pageViews" }
  }}
);

这将按作者字段分组并计算两个字段.

This groups by the author field and computes two fields.

我具有$ author = FirstName_LastName的值.现在，我不想按$ author分组，而是按共享相同姓氏的所有作者分组.

I have values for $author = FirstName_LastName.Now instead of grouping by $author, I want to group by all authors who share the same LastName.

我尝试使用$ regex对'_'之后的所有匹配字符串进行分组

I tried $regex to group by all matching strings after the '_'

$author.match(/_[a-zA-Z0-9]+$/)

db.article.aggregate(
  { $group : {
      _id : "$author".match(/_[a-zA-Z0-9]+$/),
      docsPerAuthor : { $sum : 1 },
      viewsPerAuthor : { $sum : "$pageViews" }
  }}
);

also tried the following:

 db.article.aggregate(
  { $group : {
      _id : {$author: {$regex: /_[a-zA-Z0-9]+$/}},
      docsPerAuthor : { $sum : 1 },
      viewsPerAuthor : { $sum : "$pageViews" }
  }}
);

推荐答案

实际上，没有提供这种功能的方法，或者我找不到包含该功能的合适版本.我认为这不适用于$ regexp: http://docs.mongodb.org/manual/reference/operator /regex/仅用于模式匹配.

Actually there is no such method which provides this kind of functionality or i could not find the appropriate version which contains it. That will not work with $regexp i think : http://docs.mongodb.org/manual/reference/operator/regex/ it is just for pattern matching.

jira中有一个改进请求: https://jira.mongodb.org/browse/SERVER-6773

There is an improvement request in the jira : https://jira.mongodb.org/browse/SERVER-6773

它处于打开的未解决状态.但是

It is in open unresolved state.BUT

在github中，我发现了这样的讨论: https://github.com/mongodb/mongo/pull/336

in github i found this disscussion: https://github.com/mongodb/mongo/pull/336

如果您检查此提交，请执行以下操作: https://github.com/nleite/mongo/commit/2dd175a5acda86aaad61f5eb9dab83ee19915709

And if you check this commit: https://github.com/nleite/mongo/commit/2dd175a5acda86aaad61f5eb9dab83ee19915709

它或多或少地包含您可能拥有的方法.我并没有真正理解这种改进的状态:在2.2.3中，它不起作用.

it contains more or less exactly the method you likely to have. I do not really get the point of the state of this improvement: in 2.2.3 it is not working .

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