如何在 MongoDB 中搜索子数组

我有这个 MongoDB 集合：

{ "_id" : ObjectId("123"), "from_name" : "name", "from_email" : "[email protected] /cdn-cgi/l/email-protection", "to" : [  {  "name" : "domains",  "email" : "[email protected] /cdn-cgi/l/email-protection" } ], "cc" : [ ], "subject" : "mysubject" }

我的目标是通过“to”和一些电子邮件在此集合中进行搜索。

如果你只想one那么 MongoDB 有“点符号” http://docs.mongodb.org/manual/core/document/#document-dot-notation用于访问嵌套元素：

db.collection.find({ "to.email": "[email protected] /cdn-cgi/l/email-protection" })

这将返回匹配的文档：

For more将该字段作为条件，使用$elemMatch操作员

db.collection.find(
    { "to": { 
        "$elemMatch": { 
            "email": "[email protected] /cdn-cgi/l/email-protection",
            "name": "domains",
        }
    }}
)

你可以“投影”一个singlematch 仅返回该元素：

db.collection.find({ "to.email": "[email protected] /cdn-cgi/l/email-protection" },{ "to.$": 1 })

但如果你期望more than one元素匹配，然后使用聚合框架：

db.collection.aggregate([
    // Matches the "documents" that contain this
    { "$match": { "to.email": "[email protected] /cdn-cgi/l/email-protection" } },

    // De-normalizes the array
    { "$unwind": "$to" },

    // Matches only those elements that match
    { "$match": { "to.email": "[email protected] /cdn-cgi/l/email-protection" } },

    // Maybe even group back to a singular document
    { "$group": {
        "_id": "$_id",
        "from_name": { "$first": "$name" },
        "to": { "$push": "$to" },
        "subject": { "$first": "$subject" }            
    }}

])

如果需要，可以使用所有有趣的方法来匹配和/或“过滤”数组内容以进行匹配。