Optimize none? and one? relation query methods to use LIMIT and COUNT.

Use SQL COUNT and LIMIT 1 queries for none? and one? methods if no block or limit is given,
instead of loading the entire collection to memory. The any? and many? methods already
follow this behavior.

[Eugene Gilburg & Rafael Mendonça França]

1 files changed, 18 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 8073eb99dd..6bbec7c0c0 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -271,6 +271,15 @@ module ActiveRecord
       end
     end
 
+    # Returns true if there are no records.
+    def none?
+      if block_given?
+        to_a.none? { |*block_args| yield(*block_args) }
+      else
+        empty?
+      end
+    end
+
     # Returns true if there are any records.
     def any?
       if block_given?
@@ -280,6 +289,15 @@ module ActiveRecord
       end
     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
+    end
+
     # Returns true if there is more than one record.
     def many?
       if block_given?