From b1b61d5c0b23a29ff6f9f09c8d960bf5e34eb072 Mon Sep 17 00:00:00 2001
From: Christos Trochalakis <yatiohi@ideopolis.gr>
Date: Mon, 23 Nov 2009 10:04:48 +0200
Subject: [PATCH] Added support for map-reduce

---
 lib/mongo/collection.rb | 27 +++++++++++++++++++++++++++
 test/test_collection.rb | 12 ++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/lib/mongo/collection.rb b/lib/mongo/collection.rb
index b1c01bc..f0bb8c6 100644
--- a/lib/mongo/collection.rb
+++ b/lib/mongo/collection.rb
@@ -298,6 +298,33 @@ module Mongo
       @db.drop_collection(@name)
     end
 
+    def mapreduce(map, reduce, options={})
+      case map
+      when Code
+      else
+        map = Code.new(map)
+      end
+
+      case reduce
+      when Code
+      else
+        reduce = Code.new(reduce)
+      end
+
+      hash = OrderedHash.new
+      hash['mapreduce'] = self.name
+      hash['map'] = map
+      hash['reduce'] = reduce
+      hash.merge! options
+
+      result = @db.db_command(hash)
+      if result["ok"] == 1
+      return @db[result["result"]]
+      else
+        raise Mongo::OperationFailure, "map-reduce failed: #{result['errmsg']}"
+      end
+    end
+
     # Perform a query similar to an SQL group by operation.
     #
     # Returns an array of grouped items.
diff --git a/test/test_collection.rb b/test/test_collection.rb
index 8ecdf1e..2e3ff44 100644
--- a/test/test_collection.rb
+++ b/test/test_collection.rb
@@ -265,6 +265,18 @@ class TestCollection < Test::Unit::TestCase
     assert c.closed?
   end
 
+  def test_mapreduce
+    @@test << { "user_id" => 1 }
+    @@test << { "user_id" => 2 }
+
+    m = "function() { emit(this.user_id, 1); }"
+    r = "function(k,vals) { return 1; }"
+    res = @@test.mapreduce(m, r);
+    assert res.find_one({"_id" => 1})
+    assert res.find_one({"_id" => 2})
+
+  end
+
   def test_saving_dates_pre_epoch
     begin
       @@test.save({'date' => Time.utc(1600)})