What is the best way for us to represent documents like the following in Ruby, Python, PHP, etc.

db.posts.find( { keywords :

{ $in : ["a", "b"] }

, keywords :

{ $in : ["c, d"] }

} )

Options:

Use a JSON string.
Create a hash/dict subclass that allows duplicates.
Come up with some other way of writing this in a dictionary: { $dup: { key: "keywords", values: [

{ $in: [ "a", "b" ] }

,

{ $in: [ "c", "d" ] }

] } }

• either translate at the driver level or support this in the server.