On Sep 18, 2012, at 8:04 PM, Gerald Thibault wrote: > We're using a modified version of tastypie, with all the django-specific > stuff modified to work with sqlalchemy. One of the things this offers is the > ability to submit nested resources to API endpoints, and have it recursively > build them by creating the parents, then appending the children to the > relationship as they are created. In this case, Location is built before the > phones, and location_id is set (i think) when the Phone is added to the > Location.phones relation. > > It is also possible to submit directly to the Phones endpoint and create a > phone number for an existing location which one already has the id for, in > which case the Location does not exist until the event listener (from my > first post) uses the location_id to pull up the Location, from which it > extracts the country code.
Each of those descriptions seems to indicate that a Location object is available in memory and there's nothing special about a flush(), there's no database-side triggers or defaults you're waiting on, so this issue needs to be addressed before the flush proceeds, the latest would be in the before_flush() event. > Currently, the country code extraction is working perfectly, and I am able to > see which records fail. I am unable to stop those records from being written > to the db, that is where my troubles are. How can I stop a record from being > written to the db from within the before_insert event listener? You cannot, except for raising an exception which would abort the whole transaction, as before_insert() occurs within the core of the flush process well after the flush plan has been finalized. before_flush() is provided for pre-flush modifications to the flush plan. before_insert() is not generally necessary, people frequently want to take advantage of the fact that it provides a built-in iteration of objects to be inserted, but this iteration can be done for the purposes of affecting the flush plan ahead of time within the before_flush() event, by iterating session.new. An object detected at this stage can be omitted from the insert by calling session.expunge(obj). > > On Tuesday, September 18, 2012 4:29:43 PM UTC-7, Michael Bayer wrote: > > On Sep 18, 2012, at 6:28 PM, Gerald Thibault wrote: > > > I am working with 2 models, a "Location" model, and a "Phone" model. There > > is a one-to-many relationship between them. > > > > When a phone number is submitted, I need to format it using the > > phonenumbers modules, which requires a country code, which exists on the > > Location object. So the formatting can only happen after the flush(), as I > > need to have the location_id populated, so I can grab the country code from > > the parent Location. If the formatting of the phone number fails, I want > > the entire object eliminated and not written to the db. > > At some point, the Phone is being associated with a Location object in > memory, and this would be independent of whether or not location_id is > present. The location_id can only be set, assuming this is relationship() > mechanics, if this is the case. So you shouldn't need a flush() for this to > happen, and you can perform this validation before a flush plan is > established. > > Otherwise if location_id is populated by some other means, that would point > to an area where you'd want to get Location objects present in memory ahead > of time, rather than relying upon primary keys alone. > > This might not be enough to solve your issue so feel free to add some detail > how location_id is coming into being here, such that the Location isn't > nearby. > > > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To view this discussion on the web visit > https://groups.google.com/d/msg/sqlalchemy/-/mElFMIjDpsEJ. > To post to this group, send email to sqlalchemy@googlegroups.com. > To unsubscribe from this group, send email to > sqlalchemy+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
