The load and refresh events is close to what I am looking for.
I need to be able to modify attribute of object/instance that have been
load or refreshed. I can not do the work in load or refresh event because
any changes made in the events are not track and written out on a flush/commit.
.
I am using the load event and refresh event to build build a list of
object/instance that
have been loaded or refreshed and my query class does the callback to instance
that
have been loaded or refresh. This work for query that I do but does not handle
the case
where lazy loading or deferred/refresh attribute.
What I looking for is way to get callback for any data that loaded or refreshed
once it is safe to modify
attribute. I can the use the list of instance that need to be worked based on
load and refresh events.
I only need this for ORM. I am filter stuff in event
instance_new = []
def _load_event(self, target, context):
global instance_new
if '_sa_orm_load_options' in context.execution_options:
instance_new.append(target)
On 4/27/21 4:51 PM, Mike Bayer wrote:'
they're created as the result object is iterated, which is up to how the end
user handles the result.
there's a not-yet documented execution option you can use to prebuffer the rows:
orm_execute_state.update_execution_options(prebuffer_rows=True)
result = orm_execute_state.invoke_statement()
# objects are loaded when we get here
return result
note that in your code example, you dont seem to be actually passing the loaded
ORM objects to your custm methods so I was going off of that.
or you could do what's in the example at
https://docs.sqlalchemy.org/en/14/orm/session_events.html#re-executing-statements
<https://docs.sqlalchemy.org/en/14/orm/session_events.html#re-executing-statements>
and freeze the result, then return a new one
frozen_result = orm_execute_state.invoke_statement().freeze()
# objects are loaded when we get here
return frozen_result()
you can use that freeze thing to get the results more than once, if you want to
actually iterate the objects and then return a result:
frozen_result = orm_execute_state.invoke_statement().freeze()
process_my_objects(frozen_result())
# then return it
return frozen_result()
also for a long time there's been the ORM load() event which is fired for every object as it is loaded: https://docs.sqlalchemy.org/en/14/orm/events.html?highlight=instanceevents%20load#sqlalchemy.orm.InstanceEvents.load
<https://docs.sqlalchemy.org/en/14/orm/events.html?highlight=instanceevents%20load#sqlalchemy.orm.InstanceEvents.load>
doesn't play as well with eager loaders though.
On Tue, Apr 27, 2021, at 3:43 PM, Mike Bernson wrote:
That callback look like it happening before orm instances are created. I am
looking for a
callback that is after all the instances are created. I am using the events to
get a list of instances
that need work done when they are loaded from the database.
I need the instance data and relationship data filled in before run_created is
called.
listen(mapper, 'load', self.load_instance)
listen(mapper, 'refresh', self.refresh_instance)
On 4/27/21 1:20 PM, Mike Bayer wrote:
the event that corresponds most directly here is the do_orm_execute() event:
https://docs.sqlalchemy.org/en/14/orm/session_events.html#session-execute-events
<https://docs.sqlalchemy.org/en/14/orm/session_events.html#session-execute-events>
you would want to use the "re-execute statement" feature described at:
https://docs.sqlalchemy.org/en/14/orm/session_events.html#re-executing-statements
<https://docs.sqlalchemy.org/en/14/orm/session_events.html#re-executing-statements>
the example there is a little more complex than what you need. you would have
something more like:
@event.listens_for(Session, "do_orm_execute")
def _do_orm_execute(orm_execute_state):
if orm_execute_state.is_orm_statement:
result = orm_execute_state.invoke_statement()
rdbm_events.run_created()
return result
On Tue, Apr 27, 2021, at 12:35 PM, Mike Bernson wrote:
I am moving from version 1.0.14 to version 1.4.11 of sqlalchemy.
I need to get a callback when all of the data from orm query is loaded not just
single instance.
In the 1.0 version I created the session using query_cls:
self.session = Session(bind=engine, autoflush=False,
_enable_transaction_accounting=False, autocommit=True,
query_cls=my_query)
and the query class
class my_query(Query):
def _execute_and_instances(self, context):
results = list(super(my_query, self)._execute_and_instances(context))
rdbm_events.run_created()
for instance in results:
yield instance
def instances(self, cusor, __context=None):
results = list(super(my_query, self).instances(cusor, __context))
rdbm_events.run_created()
for instance in results:
yield instance
This does not work for 1.4.11.
What is the best way to get a callback when all
the data from query or lazy/deferred loaded into instances ?
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