adding a statement pool for mysql and sqlite3

3 files changed, 102 insertions, 9 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..8ecb3cefde 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 +91,36 @@ module ActiveRecord
 
       ADAPTER_NAME = 'MySQL'
 
+      class StatementPool < ConnectionAdapters::StatementPool
+        def initialize(connection, max = 1000)
+          super
+          @cache = {}
+        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
+      end
+
       def initialize(connection, logger, connection_options, config)
         super
-        @statements = {}
+        @statements = StatementPool.new(@connection)
         @client_encoding = nil
         connect
       end
@@ -187,9 +215,6 @@ module ActiveRecord
 
       # Clears the prepared statements cache.
       def clear_cache!
-        @statements.values.each do |cache|
-          cache[:stmt].close
-        end
         @statements.clear
       end
 
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
index a90c675bf6..a4e21b714b 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
@@ -1,4 +1,5 @@
 require 'active_record/connection_adapters/abstract_adapter'
+require 'active_record/connection_adapters/statement_pool'
 require 'active_support/core_ext/string/encoding'
 
 module ActiveRecord
@@ -48,9 +49,40 @@ module ActiveRecord
         end
       end
 
+      class StatementPool < ConnectionAdapters::StatementPool
+        def initialize(connection, max = 1000)
+          super
+          @cache = {}
+        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 []=(sql, key)
+          while @max <= @cache.size
+            dealloc(@cache.shift.last[:stmt])
+          end
+          @cache[sql] = key
+        end
+
+        def clear
+          @cache.values.each do |hash|
+            dealloc hash[:stmt]
+          end
+          @cache.clear
+        end
+
+        private
+        def dealloc(stmt)
+          stmt.close unless stmt.closed?
+        end
+      end
+
       def initialize(connection, logger, config)
         super(connection, logger)
-        @statements = {}
+        @statements = StatementPool.new(@connection)
         @config = config
       end
 
@@ -107,10 +139,6 @@ module ActiveRecord
 
       # Clears the prepared statements cache.
       def clear_cache!
-        @statements.values.map { |hash| hash[:stmt] }.each { |stmt|
-          stmt.close unless stmt.closed?
-        }
-
         @statements.clear
       end
 
diff --git a/activerecord/lib/active_record/connection_adapters/statement_pool.rb b/activerecord/lib/active_record/connection_adapters/statement_pool.rb
new file mode 100644
index 0000000000..c6b1bc8b5b
--- /dev/null
+++ b/activerecord/lib/active_record/connection_adapters/statement_pool.rb
@@ -0,0 +1,40 @@
+module ActiveRecord
+  module ConnectionAdapters
+    class StatementPool
+      include Enumerable
+
+      def initialize(connection, max = 1000)
+        @connection = connection
+        @max        = max
+      end
+
+      def each
+        raise NotImplementedError
+      end
+
+      def key?(key)
+        raise NotImplementedError
+      end
+
+      def [](key)
+        raise NotImplementedError
+      end
+
+      def length
+        raise NotImplementedError
+      end
+
+      def []=(sql, key)
+        raise NotImplementedError
+      end
+
+      def clear
+        raise NotImplementedError
+      end
+
+      def delete(key)
+        raise NotImplementedError
+      end
+    end
+  end
+end