Are there restrictions on MongoDB collections property names? - mongodb

Question

I've a document structure wich contains a property named shares which is an array of objects.
Now I tried to match all documents where shared contains the matching _account string with dot notation (shares._account).
It's not working but it seems it's because of the _ char in front of property _account.
So if I put the string to search for inside the name property in that object everything works fine with dot notation.
Are there any limitations on property names?
Thought an _ is allowed because the id has it also in mongodb and for me it's a kind of convention to daclare bindings.
Example:
// Collection Item example
{
"_account": { "$oid" : "526fd2a571e1e13b4100000c" },
"_id": { "$oid" : "5279456932db6adb60000003" },
"name": "shared.jpg",
"path": "/upload/24795-4ui95s.jpg",
"preview": "/img/thumbs/24795-4ui95s.jpg",
"shared": false,
"shares": [
{
"name": "526fcb177675f27140000001",
"_account": "526fcb177675f27140000001"
},
{
"name": "tim",
"_account": "526fd29871e1e13b4100000b"
}
],
"tags": [
"grüngelb",
"farbe"
],
"type": "image/jpeg"
},
I tried to get the item with following query:
// Query example
{
"$or": [
{
"$and": [
{
"type": {
"$in": ["image/jpeg"]
}
}, {
"shares._account": "526fcb177675f27140000001" // Not working
//"shares.name": "526fcb177675f27140000001" // Working
}
]
}
]
}

Answer 1

Apart from the fact that $and can be omitted and $or is pointless "image/jpeg" != "image/jpg":
db.foo.find({
"type": {"$in": ["image/jpeg"]},
"shares._account": "526fcb177675f27140000002"
})
Or if you really want old one:
db.foo.find({
"$or": [
{
"$and": [
{
"type": {
"$in": ["image/jpeg"]
}
}, {
"shares._account": "526fcb177675f27140000002"
}
]
}
]
}
Both will return example document.

Answer 2

Your current query has some unnecessarily complicated constructs:
you don't need the $or and $and clauses ("and" is the default behaviour)
you are matching a single value using $in
The query won't find match the sample document because your query doesn't match the data:
the type field you are looking for is "image/jpg" but your sample document has "image/jpeg"
the shares._account value you are looking for is "526fcb177675f27140000001" but your sample document doesn't include this.
A simplified query that should work is:
db.shares.find(
{
"type": "image/jpeg",
"shares._account": "526fcb177675f27140000002"
}
)