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copied!<p><code>memcached</code> is nice and framework-agnostic, and you just have to write a bit of code to interact with it. The general idea of memcached is:</p> <pre><code>object = try_memcached() if not object: object = real_query() put_in_memcached(object) </code></pre> <p>That will likely be done in your SQLAlchemy abstraction, in your case. Since I'm unfamiliar with your entire platform (and only <code>memcached</code>), I did a bit of Googling.</p> <p><a href="http://www.braindonor.net/coding-blog/sqlalchemy-and-memcached/" rel="noreferrer">This blogger</a> appears to have implemented them together, and has helpfully provided a link to the code he uses. The relevant code appears to be this, which might make sense to you:</p> <pre><code>#!/usr/bin/python """ memcached objects for use with SQLAlchemy """ # This program is free software: you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program. If not, see <http://www.gnu.org/licenses/>. import memcache import sqlalchemy import sqlalchemy.orm SQLA_SESSION = sqlalchemy.orm.sessionmaker() MEMCACHED_CLIENT = memcache.Client(['127.0.0.1:11211']) class DetachedORMObject(object): """ Session-detached object for use with ORM Mapping. As the SQLAlchemy documentation indicates, creating and closing a session is not analogous to creating and closing a database connection. Connections are pooled by the database engine by default. Creating new sessions is of a minimal cost. Also, objects using this wrapper will not likely interact in with the database through the full power of SQLAlchemy queries. """ @classmethod def fetch_by_field(cls, field, value): """Fetch a mapped orm object with the give field and value""" session = SQLA_SESSION() try: class_object = session.query(cls).filter(field == value).one() except sqlalchemy.orm.exc.NoResultFound: class_object = None finally: session.close() return class_object def update(self): """Update the database with the values of the object""" session = SQLA_SESSION() session.add(self) session.commit() session.refresh(self) session.close() def refresh(self): """Refresh the object with the values of the database""" session = SQLA_SESSION() session.add(self) session.refresh(self) session.close() def delete(self): """Delete the object from the database""" session = SQLA_SESSION() session.add(self) session.delete(self) session.commit() session.close() class MemcachedObject(object): """ Object Wrapper for serializing objects in memcached. Utilizes an abstract method, get_isntance_key, to understand how to get and set objects that impliment this class. """ @classmethod def get_cached_instance(cls, instance_key): """Retrieve and return the object matching the instance_key""" key = str(cls.__module__ + '.' + cls.__name__ + ':' \ + str(instance_key)) print "Memcached Getting:", key return MEMCACHED_CLIENT.get(key) def set_cached_instance(self, time=0, min_compress_len=0): """Set the cached instance of an object""" print "Memcached Setting:", self.get_cache_key() return MEMCACHED_CLIENT.set(self.get_cache_key(), self, time, \ min_compress_len) def delete_cached_instance(self, time=0): """Wrapper for the memcached delete method""" print "Memcached Deleting:", self.get_cache_key() return MEMCACHED_CLIENT.delete(self.get_cache_key(), time) def get_cache_key(self): """Prepends the full class path of the object to the instance key""" return self.__class__.__module__ + '.' + \ self.__class__.__name__ + ':' + self.get_instance_key() def get_instance_key(self): """Get the instance key, must be implemented by child objects""" raise NotImplementedError \ ("'GetInstanceKey' method has not been defined.") class MemcachedORMObject(DetachedORMObject, MemcachedObject): """ Putting it all together now. Implements both of the above classes. Worth noting is the method for checking to see if the fetch_by_field method is invoked using a primary key of the class. The same technique is used to generate an instance key for an instance of the class. """ @classmethod def fetch_by_field(cls, field, value): """Fetch the requested object from the cache and database""" orm_object = None matched_primary_key = True for key in cls._sa_class_manager.mapper.primary_key: if field.key != key.key: matched_primary_key = False if matched_primary_key: orm_object = cls.get_cached_instance('(' + str(value) + ')') if orm_object is None: orm_object = super(MemcachedORMObject, cls). \ fetch_by_field(field, value) if orm_object is not None: orm_object.set_cached_instance() return orm_object def update(self): """Update the object in the database and memcached""" DetachedORMObject.update(self) self.set_cached_instance() def refresh(self): """Refresh the object from the database and memcached""" DetachedORMObject.refresh(self) self.set_cached_instance() def delete(self): """Delete the object from the database and memcached""" DetachedORMObject.delete(self) self.delete_cached_instance() def get_instance_key(self): """Get the instance key, implimenting abstract method in base""" key = [] for column in self._sa_instance_state.manager.mapper.primary_key: key.append('(' + str(getattr(self, column.key)) + ')') return ''.join(key) </code></pre> <p>Not sure if that helps, but there you have it. You can see that <code>memcached</code> idiom in use:</p> <pre><code> if matched_primary_key: orm_object = cls.get_cached_instance('(' + str(value) + ')') if orm_object is None: orm_object = super(MemcachedORMObject, cls). \ fetch_by_field(field, value) </code></pre>

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