1 files changed, 42 insertions, 20 deletions

diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 7d37313058..e47b7b1ed9 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -15,6 +15,7 @@ module ActiveRecord
 
     VALUE_METHODS = MULTI_VALUE_METHODS + SINGLE_VALUE_METHODS + CLAUSE_METHODS
 
+    include Enumerable
     include FinderMethods, Calculations, SpawnMethods, QueryMethods, Batches, Explain, Delegation
 
     attr_reader :table, :klass, :loaded, :predicate_builder
@@ -275,38 +276,52 @@ module ActiveRecord
 
     # Returns true if there are no records.
     def none?
-      if block_given?
-        to_a.none? { |*block_args| yield(*block_args) }
-      else
-        empty?
-      end
+      return super if block_given?
+      empty?
     end
 
     # Returns true if there are any records.
     def any?
-      if block_given?
-        to_a.any? { |*block_args| yield(*block_args) }
-      else
-        !empty?
-      end
+      return super if block_given?
+      !empty?
     end
 
     # Returns true if there is exactly one record.
     def one?
-      if block_given?
-        to_a.one? { |*block_args| yield(*block_args) }
-      else
-        limit_value ? to_a.one? : size == 1
-      end
+      return super if block_given?
+      limit_value ? to_a.one? : size == 1
     end
 
     # Returns true if there is more than one record.
     def many?
-      if block_given?
-        to_a.many? { |*block_args| yield(*block_args) }
-      else
-        limit_value ? to_a.many? : size > 1
-      end
+      return super if block_given?
+      limit_value ? to_a.many? : size > 1
+    end
+
+    # Returns a cache key that can be used to identify the records fetched by
+    # this query. The cache key is built with a fingerprint of the sql query,
+    # the number of records matched by the query and a timestamp of the last
+    # updated record. When a new record comes to match the query, or any of
+    # the existing records is updated or deleted, the cache key changes.
+    #
+    #   Product.where("name like ?", "%Cosmic Encounter%").cache_key
+    #   => "products/query-1850ab3d302391b85b8693e941286659-1-20150714212553907087000"
+    #
+    # If the collection is loaded, the method will iterate through the records
+    # to generate the timestamp, otherwise it will trigger one SQL query like:
+    #
+    #    SELECT COUNT(*), MAX("products"."updated_at") FROM "products" WHERE (name like '%Cosmic Encounter%')
+    #
+    # You can also pass a custom timestamp column to fetch the timestamp of the
+    # last updated record.
+    #
+    #   Product.where("name like ?", "%Game%").cache_key(:last_reviewed_at)
+    #
+    # You can customize the strategy to generate the key on a per model basis
+    # overriding ActiveRecord::Base#collection_cache_key.
+    def cache_key(timestamp_column = :updated_at)
+      @cache_keys ||= {}
+      @cache_keys[timestamp_column] ||= @klass.collection_cache_key(self, timestamp_column)
     end
 
     # Scope all queries to the current scope.
@@ -652,6 +667,13 @@ module ActiveRecord
       "#<#{self.class.name} [#{entries.join(', ')}]>"
     end
 
+    protected
+
+      def load_records(records)
+        @records = records
+        @loaded = true
+      end
+
     private
 
     def exec_queries