How to query nested objects?

I have a problem when querying mongoDB with nested objects notation:

db.messages.find( { headers : { From: "reservations@marriott.com" } } ).count()
0
db.messages.find( { 'headers.From': "reservations@marriott.com" }  ).count()
5

I can't see what I am doing wrong. I am expecting nested object notation to return the same result as the dot notation query. Where am I wrong?

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db.messages.find( { headers : { From: "reservations@marriott.com" } } )

This queries for documents where headers equals { From: ... } , ie contains no other fields.

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db.messages.find( { 'headers.From': "reservations@marriott.com" } )

This only looks at the headers.From field, not affected by other fields contained in, or missing from, headers .

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Dot-notation docs

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The two query mechanism work in different ways, as suggested in the docs at the section Subdocuments:

When the field holds an embedded document (ie, subdocument), you can either specify the entire subdocument as the value of a field, or “reach into” the subdocument using dot notation, to specify values for individual fields in the subdocument:

Equality matches within subdocuments select documents if the subdocument matches exactly the specified subdocument, including the field order.

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In the following example, the query matches all documents where the value of the field producer is a subdocument that contains only the field company with the value 'ABC123' and the field address with the value '123 Street' , in the exact order:

db.inventory.find( {
    producer: {
        company: 'ABC123',
        address: '123 Street'
    }
});

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