MongoDB按数组字段中的值分组 [英] MongoDB group by values in an array field
本文介绍了MongoDB按数组字段中的值分组的处理方法,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
我的资产文件采用以下格式.
I have my asset documents in the below format.
db.asset.find({}).limit(1).pretty()
{
"_id" : ObjectId("54e650a10364a65f62c0df4a"),
"_class" : "com.model.core.Asset",
"displayName" : "Bingo Rhymes For Children + More 3D Animation Nursery Rhymes & Kids' Songs",
"assetType" : "VIDEO",
"active" : true,
"originalUrl" : "https://www.youtube.com/watch?v=j-tdVvvXn9k&feature=youtube_gdata",
"groupIds" : [ ],
"folderIds" : [
"54e6507b0364a65f62c0df47",
"54e6507b0364a65f62c0df48"
]
}
如您所见,每个资产都可以具有与其关联的folderId的集合.如果我想与相关资产一起找到folderIds,mongo聚合查询将如何显示?本质上,我想按folderId对资产进行分组.
As you can see each asset can have a collection of folderId to which it is associated with. If I want to find the folderIds along with the associated assets how does the mongo aggregate query will look like? Essentially I want to group the assets by folderId.
推荐答案
首先,您需要按folderIds
字段展开,而不是按_id
分组,然后将资产_id
推送到列表assets_id
中. /p>
You first need to unwind by the folderIds
field, than group by _id
and push the asset _id
into a list assets_id
.
db.asset.aggregate([{$unwind:"$folderIds"}, {$group:{_id: "$folderIds",assets:{$push: {assets_id:"$_id"}}}}])
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