带条件的Mongodb聚合查找

本文介绍了带条件的Mongodb聚合查找的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有一个名为 article_category 的集合，它存储所有 article_id 属于具有 category_id 的类别，数据格式如下.

集合 1:article_category

{文章编号":2015110920343902，all_category_id":[5,8,10]}

然后我还有一个名为 article 的集合，用于存储我所有的帖子

集合 2:文章

{"title": "这是文章集合中的示例行"文章编号":2015110920343902，},{"title": "有些变化"article_id":2015110920343903，},{"title": "这是另一行",文章编号":2015110920343904，}

现在我想执行 MongoDB 查询以使用 regex 查找 title 而 category_id 必须等于 8.这是我的查询，但不起作用.

db.article.aggregate({$匹配:{标题:{$正则表达式:/示例/}}},{$查找:{来自:文章类别"，管道:[{ $match: { category_id: 8 } }],如:文章类别"}})

以上查询只显示符合regex但不符合category_id的记录.

有什么想法吗?

解决方案

首先是all_category_id，而不是category_id.其次，您不链接文章 - 所有文档都将具有完全相同的 article_category 数组.最后，您可能想过滤掉没有匹配类别的文章.条件管道应该更像这样:

db.article.aggregate([{ $匹配:{标题:{ $regex:/example/}} },{ $查找:{来自:文章类别"，让: {article_id: "$article_id"},管道:[{ $匹配:{$expr: { $and: [{ $in: [ 8, "$all_category_id" ] },{ $eq: [ "$article_id", "$$article_id" ] }] }} }],如:文章类别"} },{ $匹配:{$expr: { $gt: [{ $size: "$article_category"},0] }} }])

更新:

如果您不匹配 article_id，$lookup 将产生与所有文章相同的 article_category 数组.

假设您的 article_category 集合有另一个文档:

{"article_id": 0,all_category_id":[5,8,10]}

使用 { $eq: [ "$article_id", "$$article_id" ] } 在管道中，结果 article_category 是

[{文章编号":2015110920343902，"all_category_id" : [ 5, 8, 10 ]}]

没有:

[{文章编号":2015110920343902，"all_category_id" : [ 5, 8, 10 ]},{"article_id": 0,"all_category_id": [ 5, 8, 10 ]}]

如果您需要后者，那么查找请求会更简单:

db.article.find({ title: { $regex:/example/} })

和

db.article_category.find({ all_category_id: 8 })

I have a collection called article_category which store all article_id belongs to the category with category_id with data format like so.

Collection 1: article_category

{ "article_id": 2015110920343902, "all_category_id": [5,8,10] }

Then I have other collection called article which store all my post

Collection 2: article

{ "title": "This is example rows in article collection" "article_id": 2015110920343902, }, { "title": "Something change" "article_id": 2015110920343903, }, { "title": "This is another rows", "article_id": 2015110920343904, }

Now I want to perform MongoDB query to find title with regex while category_id must equal to 8. Here is my query but is not work.

db.article.aggregate( { $match: { title: { $regex: /example/ } } }, { $lookup: { from: "article_category", pipeline: [ { $match: { category_id: 8 } } ], as: "article_category" } } )

Above query only show the records which match by regex but not match by category_id.

Any idea?

解决方案

First of all, it is all_category_id, not category_id. Secondly, you don't link articles - all documents will have exactly the same article_category array. Lastly, you probably want to filter out articles that don't have matched category. The conditional pipeline should look more like this:

db.article.aggregate([ { $match: { title: { $regex: /example/ } } }, { $lookup: { from: "article_category", let: { article_id: "$article_id" }, pipeline: [ { $match: { $expr: { $and: [ { $in: [ 8, "$all_category_id" ] }, { $eq: [ "$article_id", "$$article_id" ] } ] } } } ], as: "article_category" } }, { $match: { $expr: { $gt: [ { $size: "$article_category"}, 0 ] } } } ] )

UPDATE:

If you don't match article_id, the $lookup will result with identical article_category array to all articles.

Let's say your article_category collection has another document:

{ "article_id": 0, "all_category_id": [5,8,10] }

With { $eq: [ "$article_id", "$$article_id" ] } in the pipeline the resulting article_category is

[ { "article_id" : 2015110920343902, "all_category_id" : [ 5, 8, 10 ] } ]

without:

[ { "article_id" : 2015110920343902, "all_category_id" : [ 5, 8, 10 ] }, { "article_id": 0, "all_category_id": [ 5, 8, 10 ] } ]

If the later is what you need, it would be way simpler to make to find requests:

db.article.find({ title: { $regex: /example/ } })

and

db.article_category.find({ all_category_id: 8 })