Query array of nested documents for highest value of field

Question

I'm trying to query an array of nested documents in mongodb, and also get the highest value of a particular field in that nested document. (In java)

Here is an example of the document structure, where I want to find the largest value of the "value" field in the array.

{
    "_id" : ObjectId("526d89571cd72ce9dbb6b443"),
    "array" : [ 
         {"text" : "this is a nested document", "value" : 1 },
         {"text" : "this is another nested document", "value" : 2 }
    ]
}

Answer 1

You can also try modern approach - aggregation framework:

1) Find maximum array 'value' for all elements in collection:

db.collection.aggregate([
    { $unwind: "$array" },
    { $group: { _id: "$_id", value: { $max: "$array.value" } } }
]);

2) Find maximum array 'value' for specified element:

db.collection.aggregate([
    { $match: { _id: new ObjectId("526d89571cd72ce9dbb6b443") } },
    { $unwind: "$array" },
    { $group: { _id: null, value: { $max: "$array.value" } } }
]);

Use real collection name instead of collection in these examples.

Some information on how to use aggregation in Java MongoDB driver: Java Driver and Aggregation Framework.