directly or within lazy loads, didn't consider the mapper's "get clause"
as part of the cache key, causing bound parameter mismatches if the
clause got re-generated. This clause is cached by mappers
on the fly but in highly concurrent scenarios may be generated more
than once when first accessed.
fixes#3597
relationship flag; this flag *does* have an effect when the baked
lazy loader plugin has been invoked. clarify the intent of this
flag as an "opt out" but only has an effect when the baked system
is loaded anyway. fixes#3572
simple but unusual system allows for a dramatic savings in Python
overhead for the construction and processing of orm :class:`.Query`
objects, from query construction up through rendering of a string
SQL statement.
fixes#3054
Mike Bayer