Add changelog entry and guide updates for pluck with multiple columns

activerecord/CHANGELOG.md

@@ -1,5 +1,14 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Allow ActiveRecord::Relation#pluck to accept multiple columns. Returns an
+    array of arrays containing the type casted values:
+
+        Person.pluck(:id, :name)
+        # SELECT people.id, people.name FROM people
+        # [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']]
+
+    *Jeroen van Ingen & Carlos Antonio da Silva*
+
 *   Improve the derivation of HABTM join table name to take account of nesting.
     It now takes the table names of the two models, sorts them lexically and
     then joins them, stripping any common prefix from the second table name.

activerecord/lib/active_record/relation/calculations.rb

@@ -140,6 +140,7 @@ def calculate(operation, column_name, options = {})
     #
     #   Person.pluck(:id, :name)
     #   # SELECT people.id, people.name FROM people
+    #   # => [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']]
     #
     #   Person.uniq.pluck(:role)
     #   # SELECT DISTINCT role FROM people

guides/source/active_record_querying.textile

@@ -609,8 +609,8 @@ And this will give you a single +Order+ object for each date where there are ord
 The SQL that would be executed would be something like this:
 
 <sql>
-SELECT date(created_at) as ordered_date, sum(price) as total_price 
-FROM orders 
+SELECT date(created_at) as ordered_date, sum(price) as total_price
+FROM orders
 GROUP BY date(created_at)
 </sql>
 
@@ -627,9 +627,9 @@ Order.select("date(created_at) as ordered_date, sum(price) as total_price").grou
 The SQL that would be executed would be something like this:
 
 <sql>
-SELECT date(created_at) as ordered_date, sum(price) as total_price 
-FROM orders 
-GROUP BY date(created_at) 
+SELECT date(created_at) as ordered_date, sum(price) as total_price
+FROM orders
+GROUP BY date(created_at)
 HAVING sum(price) > 100
 </sql>
 
@@ -1286,26 +1286,36 @@ Client.connection.select_all("SELECT * FROM clients WHERE id = '1'")
 
 h3. +pluck+
 
-<tt>pluck</tt> can be used to query a single column from the underlying table of a model. It accepts a column name as argument and returns an array of values of the specified column with the corresponding data type.
+<tt>pluck</tt> can be used to query a single or multiple columns from the underlying table of a model. It accepts a list of column names as argument and returns an array of values of the specified columns with the corresponding data type.
 
 <ruby>
 Client.where(:active => true).pluck(:id)
 # SELECT id FROM clients WHERE active = 1
+# => [1, 2, 3]
 
 Client.uniq.pluck(:role)
 # SELECT DISTINCT role FROM clients
+# => ['admin', 'member', 'guest']
+
+Client.pluck(:id, :name)
+# SELECT clients.id, clients.name FROM clients
+# => [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']]
 </ruby>
 
 +pluck+ makes it possible to replace code like
 
 <ruby>
 Client.select(:id).map { |c| c.id }
+# or
+Client.select(:id).map { |c| [c.id, c.name] }
 </ruby>
 
 with
 
 <ruby>
 Client.pluck(:id)
+# or
+Client.pluck(:id, :name)
 </ruby>
 
 h3. +ids+