From 39ea44cb0bea95e5008d465c67824d0cf302137f Mon Sep 17 00:00:00 2001
From: Ben Woosley <ben.woosley@gmail.com>
Date: Sat, 20 Sep 2014 17:51:56 -0700
Subject: Simplify `find_by_statement_cache` interaction down to a class-level
 ivar with a single accessor `cached_find_by_statement`.

---
 activerecord/lib/active_record/core.rb | 38 ++++++++++++++++------------------
 1 file changed, 18 insertions(+), 20 deletions(-)

(limited to 'activerecord/lib/active_record/core.rb')

diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 069aa977bf..39791e8c79 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -93,7 +93,6 @@ 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
@@ -112,11 +111,12 @@ module ActiveRecord
         super
       end
 
-      def initialize_find_by_cache
-        self.find_by_statement_cache = {}.extend(Mutex_m)
+      def initialize_find_by_cache # :nodoc:
+        @find_by_statement_cache = {}.extend(Mutex_m)
       end
 
       def inherited(child_class)
+        # initialize cache at class definition for thread safety
         child_class.initialize_find_by_cache
         super
       end
@@ -138,14 +138,11 @@ module ActiveRecord
           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)
-          }
+        statement = cached_find_by_statement(primary_key) { |params|
+          where(primary_key => params.bind).limit(1)
         }
-        record = s.execute([id], self, connection).first
+        record = statement.execute([id], self, connection).first
         unless record
           raise RecordNotFound, "Couldn't find #{name} with '#{primary_key}'=#{id}"
         end
@@ -165,19 +162,14 @@ module ActiveRecord
         # We can't cache Post.find_by(author: david) ...yet
         return super unless hash.keys.all? { |k| columns_hash.has_key?(k.to_s) }
 
-        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)
+        statement = cached_find_by_statement(hash.keys) { |params|
+          wheres = hash.keys.each_with_object({}) { |param,o|
+            o[param] = params.bind
           }
+          where(wheres).limit(1)
         }
         begin
-          s.execute(hash.values, self, connection).first
+          statement.execute(hash.values, self, connection).first
         rescue TypeError => e
           raise ActiveRecord::StatementInvalid.new(e.message, e)
         end
@@ -241,7 +233,13 @@ module ActiveRecord
 
       private
 
-      def relation #:nodoc:
+      def cached_find_by_statement(key, &block) # :nodoc:
+        @find_by_statement_cache[key] || @find_by_statement_cache.synchronize {
+          @find_by_statement_cache[key] ||= StatementCache.create(connection, &block)
+        }
+      end
+
+      def relation # :nodoc:
         relation = Relation.create(self, arel_table)
 
         if finder_needs_type_condition?
-- 
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