1 files changed, 68 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index d9aaf8597f..4571cc0786 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -94,6 +94,7 @@ module ActiveRecord
       end
 
       class_attribute :default_connection_handler, instance_writer: false
+      class_attribute :find_by_statement_cache
 
       def self.connection_handler
         ActiveRecord::RuntimeRegistry.connection_handler || default_connection_handler
@@ -107,6 +108,71 @@ module ActiveRecord
     end
 
     module ClassMethods
+      def initialize_find_by_cache
+        self.find_by_statement_cache = {}.extend(Mutex_m)
+      end
+
+      def inherited(child_class)
+        child_class.initialize_find_by_cache
+        super
+      end
+
+      def find(*ids)
+        # We don't have cache keys for this stuff yet
+        return super unless ids.length == 1
+        return super if block_given? ||
+                        primary_key.nil? ||
+                        default_scopes.any? ||
+                        columns_hash.include?(inheritance_column) ||
+                        ids.first.kind_of?(Array)
+
+        id  = ids.first
+        if ActiveRecord::Base === id
+          id = id.id
+          ActiveSupport::Deprecation.warn "You are passing an instance of ActiveRecord::Base to `find`." \
+            "Please pass the id of the object by calling `.id`"
+        end
+        key = primary_key
+
+        s = find_by_statement_cache[key] || find_by_statement_cache.synchronize {
+          find_by_statement_cache[key] ||= StatementCache.create(connection) { |params|
+            where(key => params.bind).limit(1)
+          }
+        }
+        record = s.execute([id], self, connection).first
+        unless record
+          raise RecordNotFound, "Couldn't find #{name} with '#{primary_key}'=#{id}"
+        end
+        record
+      end
+
+      def find_by(*args)
+        return super if current_scope || args.length > 1 || reflect_on_all_aggregations.any?
+
+        hash = args.first
+
+        return super if hash.values.any? { |v|
+          v.nil? || Array === v || Hash === v
+        }
+
+        key  = hash.keys
+
+        klass = self
+        s = find_by_statement_cache[key] || find_by_statement_cache.synchronize {
+          find_by_statement_cache[key] ||= StatementCache.create(connection) { |params|
+            wheres = key.each_with_object({}) { |param,o|
+              o[param] = params.bind
+            }
+            klass.where(wheres).limit(1)
+          }
+        }
+        begin
+          s.execute(hash.values, self, connection).first
+        rescue TypeError => e
+          raise ActiveRecord::StatementInvalid.new(e.message, e)
+        end
+      end
+
       def initialize_generated_modules
         super
 
@@ -267,6 +333,7 @@ module ActiveRecord
       @attributes_cache  = {}
 
       @new_record  = true
+      @destroyed   = false
 
       super
     end
@@ -299,7 +366,7 @@ module ActiveRecord
     def ==(comparison_object)
       super ||
         comparison_object.instance_of?(self.class) &&
-        id &&
+        !id.nil? &&
         comparison_object.id == id
     end
     alias :eql? :==