MongoDB. Query for array in Subdocument

Question

i am new to mongodb so please correct me if i am using the wrong terms:

I have the following document(excerpt)

{
    "_id" : ObjectId("524b0a1a7294ec8a39d4230f"),
    "name" : "Irbesartan",
    "decompositions" : [
            "IRB_444",
            "IRB_442",
            "IRB_446",
            "Valsartan acid"
    ],
    "precursor" : [
            {
                    "mass" : 429,
                    "ion" : "+H",
                    "charge" : "+",
                    "fragments" : [
                            207,
                            195,
                            180
                    ]
            },
            {
                    "mass" : 427.2252,
                    "ion" : "-H",
                    "charge" : "-",
                    "fragments" : [
                            193,
                            399
                    ]
            }
    ]
}

With

db.substances.findOne({name: "Irbesartan"}).precursor

i get the following

[
    {
            "mass" : 429,
            "ion" : "+H",
            "charge" : "+",
            "fragments" : [
                    207,
                    195,
                    180
            ]
    },
    {
            "mass" : 427.2252,
            "ion" : "-H",
            "charge" : "-",
            "fragments" : [
                    193,
                    399
            ]
    }
]

But i want to acces the fields inside, espacially the fragment array (using Mongo Shell)

Is this possible in one query?

Or is it better to store the precursor as an array instead of a subdocument?

viktortnk · Accepted Answer · 2013-10-01 19:46:22Z

1

For example query

db.substances.distinct("precursor.fragments", {name: "Irbesartan"})

gives:

[ 180, 193, 195, 207, 399 ]

or

db.substances.findOne({name: "Irbesartan"}).precursor.map(function(r) {
  return r.fragments;
})

gives

[ [ 207, 195, 180 ], [ 193, 399 ] ]

answered Oct 1, 2013 at 19:46

viktortnk

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1 Comment

hueck Over a year ago

Thank you, i will give it a try tomorrow. Is this possible db.substances.distinct("precursor.mass", {name: "Irbesartan"})?

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