Class FromCache

examples/dogpile_caching/caching_query.py:104–153

Specifies that a Query should load results from a cache.

class FromCache(UserDefinedOption):
    """Specifies that a Query should load results from a cache."""

    propagate_to_loaders = False

    def __init__(
        self,
        region="default",
        cache_key=None,
        expiration_time=None,
        ignore_expiration=False,
    ):
        """Construct a new FromCache.

        :param region: the cache region.  Should be a
         region configured in the dictionary of dogpile
         regions.

        :param cache_key: optional.  A string cache key
         that will serve as the key to the query.   Use this
         if your query has a huge amount of parameters (such
         as when using in_()) which correspond more simply to
         some other identifier.

        """
        self.region = region
        self.cache_key = cache_key
        self.expiration_time = expiration_time
        self.ignore_expiration = ignore_expiration

    # this is not needed as of SQLAlchemy 1.4.28;
    # UserDefinedOption classes no longer participate in the SQL
    # compilation cache key
    def _gen_cache_key(self, anon_map, bindparams):
        return None

    def _generate_cache_key(self, statement, parameters, orm_cache):
        """generate a cache key with which to key the results of a statement.

        This leverages the use of the SQL compilation cache key which is
        repurposed as a SQL results key.

        """
        statement_cache_key = statement._generate_cache_key()

        key = statement_cache_key.to_offline_string(
            orm_cache._statement_cache, statement, parameters
        ) + repr(self.cache_key)
        # print("here's our key...%s" % key)
        return key


class RelationshipCache(FromCache):