mongodb array matching
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How do I accomplish the following?

    db.test.save( {a: [1,2,3]} );

    db.test.find( {a: [1,2,3,4]} );  //must match because it contains all required values [1, 2, 3]
    db.test.find( {a: [1,2]} );  //must NOT match because the required value 3 is missing

I know about $in and $all but they work differently.