1 files changed, 35 insertions, 4 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index e9bdcc2104..a1824fe396 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -1,4 +1,5 @@
 require 'active_record/connection_adapters/abstract_mysql_adapter'
+require 'active_record/connection_adapters/statement_pool'
 require 'active_support/core_ext/hash/keys'
 
 gem 'mysql', '~> 2.8.1'
@@ -90,9 +91,42 @@ module ActiveRecord
 
       ADAPTER_NAME = 'MySQL'
 
+      class StatementPool < ConnectionAdapters::StatementPool
+        def initialize(connection, max = 1000)
+          super
+          @cache = Hash.new { |h,pid| h[pid] = {} }
+        end
+
+        def each(&block); cache.each(&block); end
+        def key?(key);    cache.key?(key); end
+        def [](key);      cache[key]; end
+        def length;       cache.length; end
+        def delete(key);  cache.delete(key); end
+
+        def []=(sql, key)
+          while @max <= cache.size
+            cache.shift.last[:stmt].close
+          end
+          cache[sql] = key
+        end
+
+        def clear
+          cache.values.each do |hash|
+            hash[:stmt].close
+          end
+          cache.clear
+        end
+
+        private
+        def cache
+          @cache[$$]
+        end
+      end
+
       def initialize(connection, logger, connection_options, config)
         super
-        @statements = {}
+        @statements = StatementPool.new(@connection,
+                                        config.fetch(:statement_limit) { 1000 })
         @client_encoding = nil
         connect
       end
@@ -187,9 +221,6 @@ module ActiveRecord
 
       # Clears the prepared statements cache.
       def clear_cache!
-        @statements.values.each do |cache|
-          cache[:stmt].close
-        end
         @statements.clear
       end