How can I query an indexed object list in mongodb? - mongodb

Question

I have some documents in the "company" collection structured this way :
[
{
"company_name": "Company 1",
"contacts": {
"main": {
"email": "main#company1.com",
"name": "Mainuser"
},
"store1": {
"email": "store1#company1.com",
"name": "Store1 user"
},
"store2": {
"email": "store2#company1.com",
"name": "Store2 user"
}
}
},
{
"company_name": "Company 2",
"contacts": {
"main": {
"email": "main#company2.com",
"name": "Mainuser"
},
"store1": {
"email": "store1#company2.com",
"name": "Store1 user"
},
"store2": {
"email": "store2#company2.com",
"name": "Store2 user"
}
}
}
]
I'm trying to retrieve the doc that have store1#company2.com as a contact but cannot find how to query a specific value of a specific propertie of an "indexed" list of objects.
My feeling is that the contacts lists should not not be indexed resulting in the following structure :
{
"company_name": "Company 1",
"contacts": [
{
"email": "main#company1.com",
"name": "Mainuser",
"label": "main"
},
{
"email": "store1#company1.com",
"name": "Store1 user",
"label": "store1"
},
{
"email": "store2#company1.com",
"name": "Store2 user",
"label": "store2"
}
]
}
This way I can retrieve matching documents through the following request :
db.company.find({"contacts.email":"main#company1.com"})
But is there anyway to do a similar request on document using the previous structure ?
Thanks a lot for your answers!
P.S. : same question for documents structured this way :
{
"company_name": "Company 1",
"contacts": {
"0": {
"email": "main#company1.com",
"name": "Mainuser"
},
"4": {
"email": "store1#company1.com",
"name": "Store1 user"
},
"1": {
"email": "store2#company1.com",
"name": "Store2 user"
}
}
}

Answer 1

Short answer: yes, they can be queried but it's probably not what you want and it's not going to be really efficient.
The document structure in the first and third block is basically the same - you have an embedded document. The only difference between are the name of the keys in the contacts object.
To query document with that kind of structure you will have to do a query like this:
db.company.find({ $or : [
{"contacts.main.email":"main#company1.com"},
{"contacts.store1.email":"main#company1.com"},
{"contacts.store2.email":"main#company1.com"}
]});
This query will not be efficient, especially if you have a lot of keys in the contacts object. Also, creating a query will be unnecessarily difficult and error prone.
The second document structure, with an array of embedded objects, is optimal. You can create a multikey index on the contacts array which will make your query faster. The bonus is that you can use a short and simple query.

Answer 2

I think the easiest is really to shape your document using the structure describe in your 2nd example : (I have not fixed the JSON)
{
"company_name": "Company 1",
"contacts":{[
{"email":"main#company1.com","name":"Mainuser", "label": "main", ...}
{"email":"store1#company1.com","name":"Store1 user", "label": "store1",...}
{"email":"store2#company1.com","name":"Store2 user", "label": "store2",...}
]}
}
like that you can easily query on email independently of the "label".
So if you really want to use the other structure, (but you need to fix the JSON too) you will have to write more complex code/aggregation pipeline, since we do not know the name and number of attributes when querying the system. Theses structures are also probably hard to use by the developers independently of MongoDB queries.
Since it was not clear let me show what I have in mind
db.company.save(
{
"company_name": "Company 1",
"contacts":[
{"email":"main#company1.com","name":"Mainuser", "label": "main"},
{"email":"store1#company1.com","name":"Store1 user", "label": "store1"},
{"email":"store2#company1.com","name":"Store2 user", "label": "store2"}
]
}
);
db.company.save(
{
"company_name": "Company 2",
"contacts":[
{"email":"main#company2.com","name":"Mainuser", "label": "main"},
{"email":"store1#company2.com","name":"Store1 user", "label": "store1"},
{"email":"store2#company2.com","name":"Store2 user", "label": "store2"}
]
}
);
db.company.ensureIndex( { "contacts.email" : 1 } );
db.company.find( { "contacts.email" : "store1#company2.com" } );
This allows you to store many emails, and query with an index.