MongoRuby and Mongodb

Question

Can anybody say me why this works in mongodb

db.sub_count.update({"subject":"petad","count":1},{$inc:{"count":1}})

But this doesn't work on ruby

sub_count.update({"subject" => "petad", "count"=> 1},{$inc => {"count" => 1}})

where I get the error

/lib/bson/bson_c.rb:24:in `serialize': keys must be strings or symbols (TypeError)

Answer 1

The query should be:

sub_count.update({...}, {"$inc" => {"count" => 1}}) # And not :$inc

$inc is not a valid symbol (or string) and that's why you see the error.

Aside: I'm not sure if this works: :"$inc" You can define a symbol this way but there is no mention in the Ruby driver docs that a symbol can be used for the atomic operators and since I haven't tried it at any point, I'm not sure.