Mongo Group function call in Ruby - ruby

Question

I have a mongodb collection like this
{"assigneeId" => 1000, "status" => 3, "starttime" => "2014 Feb 25", "numofdays => 6}
{"assigneeId" => 1000, "status" => 2, "starttime" => "2014 Jan 10", "numofdays => 6}
{"assigneeId" => 1000, "status" => 3, "starttime" => "2014 Jan 1", "numofdays => 20}
I wrote a MongoDB query to group the above collection with assigneeId whose status is 3 and add the value of numofdays like this
db.events.group ( { key: {assigneeId:1}, cond: {status: {$gte: 3}}, reduce: function (curr, result) {result.total++; result.numofdays += curr.numofdays;}, initial: {total:0, numofdays:0} })
This gives the output as expected from the Mongodb cli.
When I write the ruby code for executing the same query, I could not make it work. Am getting lot of different hits for similar problem but none of the format seems to work. I could not go past the syntax error in ruby for grouping function. Please note I am not using mongoid. If I could get this work with Aggregation framework, that is also fine with me.
This is the ruby query I wrote and the error for the same.
#events_h.group (
:cond => {:status => { '$in' => ['3']}},
:key => 'assigneeId',
:initial => {count:0},
:reduce => "function(x, y) {y.count += x.count;}"
)
Error I am getting
analyze.rb:43: syntax error, unexpected ',', expecting ')'
out = #events_h.group (["assigneeId"], { }, { }, "function() { }")
^
analyze.rb:43: syntax error, unexpected ')', expecting keyword_end
analyze.rb:83: syntax error, unexpected end-of-input, expecting keyword_end
Any help is much appreciated.
Thanks

Answer 1

The following test includes solutions for using both methods, group and aggregate.
I recommend that you use aggregate, it is faster and avoids JavaScript and consuming a V8 engine.
Hope that this helps.
test.rb
require 'mongo'
require 'test/unit'
class MyTest < Test::Unit::TestCase
def setup
#events_h = Mongo::MongoClient.new['test']['events_h']
#docs = [
{"assigneeId" => 1000, "status" => 3, "starttime" => "2014 Feb 25", "numofdays" => 6},
{"assigneeId" => 1000, "status" => 2, "starttime" => "2014 Jan 10", "numofdays" => 6},
{"assigneeId" => 1000, "status" => 3, "starttime" => "2014 Jan 1", "numofdays" => 20}]
#events_h.remove
#events_h.insert(#docs)
end
test "group" do
result = #events_h.group(
:cond => {:status => {'$in' => [3]}},
:key => 'assigneeId',
:initial => {numofdays: 0},
:reduce => "function(x, y) {y.numofdays += x.numofdays;}"
)
assert_equal(26, result.first['numofdays'])
puts "group: #{result.inspect}"
end
test "aggregate" do
result = #events_h.aggregate([
{'$match' => {:status => {'$in' => [3]}}},
{'$group' => {'_id' => '$status', 'numofdays' => {'$sum' => '$numofdays'}}}
])
assert_equal(26, result.first['numofdays'])
puts "aggregate: #{result.inspect}"
end
end
$ ruby test.rb
Loaded suite test
Started
aggregate: [{"_id"=>3, "numofdays"=>26}]
.group: [{"assigneeId"=>1000.0, "numofdays"=>26.0}]
.
Finished in 0.010575 seconds.
2 tests, 2 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed
189.13 tests/s, 189.13 assertions/s