a Query.

The rest of what's here are standard SQLAlchemy and

Beaker constructs.

"""

import beaker

from beaker.exceptions import BeakerException

from sqlalchemy.orm.interfaces import MapperOption

from sqlalchemy.orm.query import Query

from sqlalchemy.sql import visitors

class CachingQuery(Query):

    """A Query subclass which optionally loads full results from a Beaker

    cache region.

    The CachingQuery stores additional state that allows it to consult

    a Beaker cache before accessing the database:

    * A "region", which is a cache region argument passed to a

      Beaker CacheManager, specifies a particular cache configuration

      (including backend implementation, expiration times, etc.)

        raise ValueError("This Query does not have caching "

                         "parameters configured.")

    region, namespace, cache_key = query._cache_parameters

    namespace = _namespace_from_query(namespace, query)

    if cache_key is None:

        # cache key - the value arguments from this query's parameters.

        args = _params_from_query(query)

        args.append(query._limit)

        args.append(query._offset)

    if cache_key is None:

        raise Exception('Cache key cannot be None')

    # get cache

    #cache = query.cache_manager.get_cache_region(namespace, region)

    cache = get_cache_region(namespace, region)

    # optional - hash the cache_key too for consistent length

    # import uuid

    # cache_key= str(uuid.uuid5(uuid.NAMESPACE_DNS, cache_key))

    return cache, cache_key