mongodb query subset of an array

Question

I have a field _keywords which is an array of strings. I want to get documents of which _keywords are super-set of the query array.

For example

Answer 1

Short answer: $all operator.
To query documents with array with superset of ['foo1', 'foo2'], use:
db.article.find( { '_keywords': { $all: ['foo1', 'foo2'] } } );