Hi,
We have a use case where we would like to have "incremental updates"
to existing session objects (ie. populate_existing()-type behaviour
where existing object's lazy-loaded attributes are not reset by
subsequent populate_existing queries).
We have come up with a solution by implementing a subclassed
LazyLoader strategy that returns a No-op function in the
"create_row_processor" (basically skipping line 474 in
sqlalchemy.orm.strategies in version 0.5.8). Is this a safe place to
put this functionality? Note that this session is never used for
flushing, it is used as a read-only caching session.
from sqlalchemy.orm.strategies import LazyLoader
class IncrementalLazyLoader(LazyLoader):
def create_row_processor(self, *args, **kwargs):
if self.is_class_level:
def new_execute(state, dict_, row, **flags):
pass
return (new_execute, None)
else:
return super(IncrementalLazyLoader,
self).create_row_processor(*args, **kwargs)
This special strategy is used on lazy mapped properties by passing a
"strategy_class" to the relation() call.
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