我是 mongodb 的新手，我有两个这样的集合:
第一个集合名称是 A
{
"_id": "1234",
"versions": [{
"owner_id": ObjectId("100000"),
"versions": 1,
"type" : "info",
"items" : ["item1","item3","item7"]
},
{
"owner_id": ObjectId("100001"),
"versions": 2,
"type" : "bug",
"OS": "Ubuntu",
"Dependencies" : "Trim",
"items" : ["item1","item7"]
}
]}
第二个系列名称是 B
{ "_id": ObjectId("100000"), "email": "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="ed8c8f8ead959497c38e8280" rel="noreferrer noopener nofollow">[email protected]</a>" } { "_id": ObjectId("100001"), "email": "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="98fafafbd8e0e1e2b6fbf7f5" rel="noreferrer noopener nofollow">[email protected]</a>"}
预期输出是:
{
"_id": "1234",
"versions":[{
"owner_id": "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="33525150734b4a491d505c5e" rel="noreferrer noopener nofollow">[email protected]</a>",
"versions": 1,
"type" : "info",
"items" : ["item1","item3","item7"]
},
{
"owner_id": "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="aecccccdeed6d7d480cdc1c3" rel="noreferrer noopener nofollow">[email protected]</a>",
"versions": 2,
"type" : "bug",
"OS": "Ubuntu",
"Dependencies" : "Trim",
"items" : ["item1","item7"]
}
] }
我使用了 mongo $lookup 但没有得到所需的输出 请帮忙。
谢谢!!!
最佳答案
您需要将 $unwind 版本、$lookup 与 foreignField 上的另一个集合、$project 进行比较匹配数组中的第一个元素 $group 以原始文档格式返回
收藏一
> db.a.find()
{ "_id" : "1234", "versions" : [ { "owner_id" : "100000" }, { "owner_id" : "100001" }, { "owner_id" : "100001" } ] }
集合b
> db.b.find()
{ "_id" : "100000", "email" : "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="dbbab9b89ba3a2a1f5b8b4b6" rel="noreferrer noopener nofollow">[email protected]</a>" }
{ "_id" : "100001", "email" : "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="06646465467e7f7c2865696b" rel="noreferrer noopener nofollow">[email protected]</a>" }
聚合管道
> db.a.aggregate(
[
{$unwind:"$versions"},
{$lookup : {from : "b", "localField":"versions.owner_id", "foreignField":"_id", as :"out"}},
{$project : {"_id":1, "versions.owner_id":{$arrayElemAt:["$out.email",0]}}},
{$group:{_id:"$_id", versions : {$push : "$versions"}}}
]
).pretty()
输出
{
"_id" : "1234",
"versions" : [
{
"owner_id" : "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="e6878485a69e9f9cc885898b" rel="noreferrer noopener nofollow">[email protected]</a>"
},
{
"owner_id" : "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="87e5e5e4c7fffefda9e4e8ea" rel="noreferrer noopener nofollow">[email protected]</a>"
},
{
"owner_id" : "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="8fededeccff7f6f5a1ece0e2" rel="noreferrer noopener nofollow">[email protected]</a>"
}
]
}
关于json - Mongodb 聚合其他集合的匹配字段的 JSON 数组字段，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/48166829/