CODEWITHSUNDEEP
mongodbmongodb-queryaggregation-framework
Milos Cuculovic
Milos Cuculovic

Reputation: 20223

How to search sub arrays in MongoDB

I have this MongoDB collection:

{ "_id" : ObjectId("123"), "from_name" : "name", "from_email" : "[email protected]", "to" : [  {  "name" : "domains",  "email" : "[email protected]" } ], "cc" : [ ], "subject" : "mysubject" }

My goal is to search in this collection by the "to" with some email.

Upvotes: 0

Views: 737

Answers (1)

Neil Lunn
Neil Lunn

Reputation: 151092

If you only want one field then MongoDB has "dot notation" for accessing nested elements:

db.collection.find({ "to.email": "[email protected]" })

And this will return documents that match:

For more that one field as a condition, use the $elemMatch operator

db.collection.find(
    { "to": { 
        "$elemMatch": { 
            "email": "[email protected]",
            "name": "domains",
        }
    }}
)

And you can "project" a single match to just return that element:

db.collection.find({ "to.email": "[email protected]" },{ "to.$": 1 })

But if you expect more than one element to match, then you use the aggregation framework:

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

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

    // Matches only those elements that match
    { "$match": { "to.email": "[email protected]" } },

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

])

All fun ways to match on and/or "filter" the content of an array for matches if required.

Upvotes: 2

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