Passing BSON directly to MongoDB using the mong-ruby-driver? - ruby

Question

Is there a way to pass a BSON object directly into the .find() in the mongo-ruby-driver?
At the moment I have a basic sinatra app that takes URL encoded JSON and parses it into the .find() but I would ideally like to give it straight BSON:
require 'sinatra'
require 'mongo'
require 'json'
include Mongo
db = MongoClient.new().db('test')
get '/' do
if request[:query]
query = JSON.parse(CGI::unescape(request[:query]))
db.collection('test_collection').find(query).to_a.to_json
end
end
So essentially have something along the lines of BSON.parse(url-encoded-query) and be able to pass that into a .find() returning the result.
Example URL: http://localhost:4567/?query=%7B%20%22name%22%20%3A%20%22john%20doe%22%20%7D
Current query: { "name" : "john doe" }
BSON query: { name: /.*john.*/, interests: [ 'fishing', 'golf' ]} that I'd like to work

Answer 1

The following test script demonstrates how to use the $elemMatch operator as a projection. Please note that the Collection#find method takes arbitrary documents for both the "selector" formal parameter and for the "opts" :fields option.
MongoDB documents are mapped to/from Ruby Hash objects, and these documents can fully incorporate MongoDB operators.
elemmatch_projection.rb
#!/usr/bin/env ruby
# Ruby translation of example from http://docs.mongodb.org/manual/reference/projection/elemMatch/
require 'mongo'
coll = Mongo::MongoClient.new['test']['students']
coll.remove
coll.insert({
zipcode: 63109,
dependents: [
{ name: "john", school: 102, age: 10 },
{ name: "jess", school: 102, age: 11 },
{ name: "jeff", school: 108, age: 15 }
]
})
p coll.find( { zipcode: 63109 }, :fields => { dependents: { '$elemMatch' => { school: 102 } } } ).to_a
ruby elemmatch_projection.rb
[{"_id"=>BSON::ObjectId('50eab29929daeb05ae000001'), "dependents"=>[{"name"=>"john", "school"=>102, "age"=>10}]}]
This is another answer because the question has been significantly clarified by the OP.
Hope that this helps you understand how to use MongoDB documents and operators in Ruby.

Answer 2

Your issue has more to do with parsing JSON or Ruby (Regexp) than with BSON. Your original question causes confusion by jumping directly to BSON. With the current Ruby driver, BSON is not directly exposed to the application writer, but mapped as naturally as possible from and to Ruby objects.
JSON is strictly limited and safe for parsing. Adding parsing for Regexp moves beyond this.
You can do what you want unsafely using Kernel#eval. This will parse your Regexp, but it will also parse exec, system, backticks, etc. For a public application with arbitrary user input, you will have to do something safer.
Also note, the differences between the following lines, which highlights semantics with both Ruby and MongoDB:
{ interests: [ 'fishing', 'golf' ] }
The above exactly matches interests iff they are exactly [ 'fishing', 'golf' ]. no more, no less, no other order.
{ interests: { '$in' => [ 'fishing', 'golf' ] } }
The above matches interests if interests have either 'fishing' or 'golf', any order, any position, any extras. Note that the string key '$in' requires the original => syntax.
Hope that this helps your understanding, and please feel free to followup with clarifying questions.
The following is a working example.
myapp.rb
require 'sinatra'
require 'mongo'
require 'json'
include Mongo
db = MongoClient.new().db('test')
get '/' do
if request[:query]
query = eval CGI::unescape(request[:query])
docs = db.collection('test_collection').find(query).to_a.to_json
"docs=#{docs}"
end
end
myapp_test.rb
require 'myapp'
require 'test/unit'
require 'rack/test'
require 'open-uri'
ENV['RACK_ENV'] = 'test'
class MyAppTest < Test::Unit::TestCase
include Rack::Test::Methods
def setup
#db ||= Mongo::MongoClient.new['test']
#coll ||= #db['test_collection']
#coll.remove
#coll.insert({name: 'john doe', interests: [ 'fishing', 'golf' ]})
end
def app
Sinatra::Application
end
def query_test(query)
uri = "http://localhost:4567/?query=#{URI::encode(query)}"
puts "uri=#{uri}"
get uri
puts last_response.body
assert_match(/^docs=/, last_response.body)
end
def test_john_doe
query_test("{ name: 'john doe'}")
end
def test_regexp
query_test("{ name: /.*john.*/, interests: [ 'fishing', 'golf' ]}")
end
end
ruby -I. myapp_test.rb
Run options:
# Running tests:
uri=http://localhost:4567/?query=%7B%20name:%20/.*john.*/,%20interests:%20[%20'fishing',%20'golf'%20]%7D
docs=[{"_id":{"$oid": "50e9e60029daeb0be1000001"},"name":"john doe","interests":["fishing","golf"]}]
.uri=http://localhost:4567/?query=%7B%20name:%20'john%20doe'%7D
docs=[{"_id":{"$oid": "50e9e60129daeb0be1000002"},"name":"john doe","interests":["fishing","golf"]}]
.
Finished tests in 0.065822s, 30.3850 tests/s, 60.7700 assertions/s.
2 tests, 4 assertions, 0 failures, 0 errors, 0 skips