1 files changed, 41 insertions, 3 deletions
diff --git a/activerecord/lib/active_record/result.rb b/activerecord/lib/active_record/result.rb
index a7a035fe46..d0f1cb5b75 100644
--- a/activerecord/lib/active_record/result.rb
+++ b/activerecord/lib/active_record/result.rb
@@ -3,8 +3,31 @@ module ActiveRecord
   # This class encapsulates a Result returned from calling +exec_query+ on any
   # database connection adapter. For example:
   #
-  #   x = ActiveRecord::Base.connection.exec_query('SELECT * FROM foo')
-  #   x # => #<ActiveRecord::Result:0xdeadbeef>
+  #   result = ActiveRecord::Base.connection.exec_query('SELECT id, title, body FROM posts')
+  #   result # => #<ActiveRecord::Result:0xdeadbeef>
+  #
+  #   # Get the column names of the result:
+  #   result.columns
+  #   # => ["id", "title", "body"]
+  #
+  #   # Get the record values of the result:
+  #   result.rows
+  #   # => [[1, "title_1", "body_1"],
+  #         [2, "title_2", "body_2"],
+  #         ...
+  #        ]
+  #
+  #   # Get an array of hashes representing the result (column => value):
+  #   result.to_hash
+  #   # => [{"id" => 1, "title" => "title_1", "body" => "body_1"},
+  #         {"id" => 2, "title" => "title_2", "body" => "body_2"},
+  #         ...
+  #        ]
+  #
+  #   # ActiveRecord::Result also includes Enumerable.
+  #   result.each do |row|
+  #     puts row['title'] + " " + row['body']
+  #   end
   class Result
     include Enumerable
 
@@ -62,6 +85,7 @@ module ActiveRecord
     end
 
     private
+
     def hash_rows
       @hash_rows ||=
         begin
@@ -69,7 +93,21 @@ module ActiveRecord
           # used as keys in ActiveRecord::Base's @attributes hash
           columns = @columns.map { |c| c.dup.freeze }
           @rows.map { |row|
-            Hash[columns.zip(row)]
+            # In the past we used Hash[columns.zip(row)]
+            #  though elegant, the verbose way is much more efficient
+            #  both time and memory wise cause it avoids a big array allocation
+            #  this method is called a lot and needs to be micro optimised
+            hash = {}
+
+            index = 0
+            length = columns.length
+
+            while index < length
+              hash[columns[index]] = row[index]
+              index += 1
+            end
+
+            hash
           }
         end
     end