从子文档数组中检索字段值 [英] Retrieve field value from array of sub document
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问题描述
我有一些像这样的文件:
I have some documents like this:
{
"hash": "14a076f9f6cecfc58339330eeb492e267f63062f6d5f669c7cdbfecf9eb4de32",
"started_services": [],
"deleted_files": [],
"software": {
"adobe" : {
"licenses" : [
{ "key": "2384723",
"date": "26-10-2012"
},
{ "key": "23888823",
"date": "09-11-2012"
}
]
}
}
}
如何仅检索哈希值和键"值列表?
How do I retrieve just the hash value and the list of "key" values?
我做了以下操作,但是,如您所见,结果包含了我不想要的完整路径.
I did the following, but, as you see, the result has the entire path which I do not want.
> db.repository.find({"$and": [{"datetime_int": {"$gte": 1451952000}},{"software.adobe.licenses.key" : { $exists : true}}]}, {hash:1, "software.adobe.licenses.key":1, _id:0}).limit(10)
{ "hash" : "a1532e0609aaf6acfa9e505e93af0bee0856a9a67398aeaa72aa6eb2fffd134e", "software" : { "adobe" : { "licenses" : [ { "key" : "2008350" }, { "key" : "2018350" }, { "key" : "2028350" }, { "key" : "2038350" }, { "key" : "2048350" }, { "key" : "2058350" }, { "key" : "2068350" }, { "key" : "2078350" }...]}}}
我想要的结果应如下所示:
The result I want should look like this:
{"hash": "a1532e0609aaf6acfa9e505e93af0bee0856a9a67398aeaa72aa6eb2fffd134e",
"key": ["2008350", "2018350", "2028350", "2038350", "2048350", "2058350", "2068350", "2078350"]
}
我该怎么做?
推荐答案
您可以使用聚合框架来做到这一点.
You can do this with the aggregation framework.
db.repository.aggregate([
{ "$match": {
"datetime_int": { "$gte": 1451952000 },
"software.adobe.licenses.key" : { "$exists" : true }
}},
{ "$project": {
"hash": 1,
"key": {
"$map": {
"input": "$software.adobe.licenses",
"as": "soft",
"in": "$$soft.key"
}
}
}}
])
从MongoDB 3.2开始,您可以直接投影子文档数组字段.
Starting From MongoDB 3.2 you can directly project the sub-document array field.
{ "$project": { "hash": 1, "key": "$software.adobe.licenses.key"}}
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