Started work on a per-request query cache

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1267 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/lib/active_record.rb

@@ -67,3 +67,5 @@
 require 'active_record/connection_adapters/sqlserver_adapter'
 require 'active_record/connection_adapters/db2_adapter'
 require 'active_record/connection_adapters/oci_adapter'
+
+require 'active_record/query_cache'

activerecord/lib/active_record/query_cache.rb

@@ -0,0 +1,64 @@
+module ActiveRecord
+  class QueryCache
+    def initialize(connection)
+      @connection = connection
+      @query_cache = {}
+    end
+
+    def clear_query_cache
+      @query_cache = {}
+    end
+
+    def select_all(sql, name = nil)
+      @query_cache[sql] ||= @connection.select_all(sql, name)
+    end
+
+    def select_one(sql, name = nil)
+      @query_cache[sql] ||= @connection.select_one(sql, name)
+    end
+
+    def columns(table_name, name = nil)
+      @query_cache["SHOW FIELDS FROM #{table_name}"] ||= @connection.columns(table_name, name)
+    end
+
+    def insert(sql, name = nil, pk = nil, id_value = nil)
+      clear_query_cache
+      @connection.insert(sql, name, pk, id_value)
+    end
+
+    def update(sql, name = nil)
+      clear_query_cache
+      @connection.update(sql, name)
+    end
+
+    def delete(sql, name = nil)
+      clear_query_cache
+      @connection.delete(sql, name)
+    end
+
+    private
+      def method_missing(method, *arguments)
+        @connection.send(method, *arguments)
+      end
+  end
+
+  class Base
+    # Set the connection for the class with caching on
+    def self.connection=(spec)
+      raise ConnectionNotEstablished unless spec
+
+      conn = spec.config[:query_cache] ?
+        QueryCache.new(self.send(spec.adapter_method, spec.config)) :
+        self.send(spec.adapter_method, spec.config)
+
+      Thread.current['active_connections'] ||= {}
+      Thread.current['active_connections'][self] = conn
+    end
+  end
+
+  class AbstractAdapter
+    # Stub method to be able to treat the connection the same whether the query cache has been turned on or not
+    def clear_query_cache
+    end
+  end
+end