Method _generate_cache_attrs

lib/sqlalchemy/sql/cache_key.py:149–219

generate cache key dispatcher for a new class. This sets the _generated_cache_key_traversal attribute once called so should only be called once per class.

(
        cls,
    )

    @classmethod
    def _generate_cache_attrs(
        cls,
    ) -> Union[_CacheKeyTraversalDispatchType, Literal[CacheConst.NO_CACHE]]:
        """generate cache key dispatcher for a new class.

        This sets the _generated_cache_key_traversal attribute once called
        so should only be called once per class.

        """
        inherit_cache = cls.__dict__.get("inherit_cache", None)
        inherit = bool(inherit_cache)

        if inherit:
            _cache_key_traversal = getattr(cls, "_cache_key_traversal", None)
            if _cache_key_traversal is None:
                try:
                    assert issubclass(cls, HasTraverseInternals)
                    _cache_key_traversal = cls._traverse_internals
                except AttributeError:
                    cls._generated_cache_key_traversal = NO_CACHE
                    return NO_CACHE

            assert _cache_key_traversal is not NO_CACHE, (
                f"class {cls} has _cache_key_traversal=NO_CACHE, "
                "which conflicts with inherit_cache=True"
            )

            # TODO: wouldn't we instead get this from our superclass?
            # also, our superclass may not have this yet, but in any case,
            # we'd generate for the superclass that has it.   this is a little
            # more complicated, so for the moment this is a little less
            # efficient on startup but simpler.
            return _cache_key_traversal_visitor.generate_dispatch(
                cls,
                _cache_key_traversal,
                "_generated_cache_key_traversal",
            )
        else:
            _cache_key_traversal = cls.__dict__.get(
                "_cache_key_traversal", None
            )
            if _cache_key_traversal is None:
                _cache_key_traversal = cls.__dict__.get(
                    "_traverse_internals", None
                )
                if _cache_key_traversal is None:
                    cls._generated_cache_key_traversal = NO_CACHE
                    if (
                        inherit_cache is None
                        and cls._hierarchy_supports_caching
                    ):
                        util.warn(
                            "Class %s will not make use of SQL compilation "
                            "caching as it does not set the 'inherit_cache' "
                            "attribute to ``True``.  This can have "
                            "significant performance implications including "
                            "some performance degradations in comparison to "
                            "prior SQLAlchemy versions.  Set this attribute "