Re: [sqlalchemy] ORM events order
Thank you very much On Thursday, December 5, 2013 5:20:57 PM UTC, Michael Bayer wrote: > > > On Dec 5, 2013, at 12:14 PM, Tim Kersten > > wrote: > > > thank you. > > > > What of the relative ordering of the different ORM event types? i.e. > > > > before_flush > > before_delete > > after_flush > > etc > > > > When looking at before_flush I see the before_delete has not yet been > fired, yet is has been fired in the after_flush. Is this guaranteed to > always be the case? > > yes, before_flush and after_flush provide boundaries around the mechanics > of the flush itself. before_delete as well as the other mapper-level > events like before_update before_insert after_update etc. are all within > the flush mechanics. > > you can’t necessarily rely upon the ordering of insert/update/delete > events within the flush however, relative to different objects and > especially across different kinds of objects. The mapper-level flush > events are fired right as individual batches of objects are being prepared > for INSERT/UPDATE/DELETE statements. > > > > > > > > > > On 5 Dec 2013, at 16:01, Michael Bayer > > > > wrote: > > > >> > >> On Dec 5, 2013, at 10:51 AM, Tim Kersten > > wrote: > >> > >>> Hi Folks, > >>> > >>> Is the order ORM events ( > http://docs.sqlalchemy.org/en/rel_0_9/orm/events.html ) are fired in > deterministic and guaranteed to be the same every time? I've searched the > docs and google but couldn't anything relating to their relative order. > >> > >> > >> the events are ordered. when you do an event.listen it appends the > event listener to a list of listeners. the events are fired from the > beginning of the list on forward.there’s actually an undocumented > argument to event.listen() “insert=True” that will cause the listener to be > inserted at position zero rather than appended. > >> > >> the reason the order of events is not really mentioned much is because > there’s complex cases where the order of listener application has not been > evaluated or tested. When you make use of mapper or instrumentation events > against un-mapped base classes and such, the actual append() operation > doesn’t occur until later, when classes are actually mapped, and this works > by shuttling the event listener functions around to those classes. In > these cases we don’t as yet have guarantees in place as to the order of the > listeners being first applied, e.g. if you had a class that is a product of > two mixins, and each mixin has listeners applied to it, that sort of thing. > >> > >> however, the order of listeners once applied should definitely be the > same each time assuming no changes to the listener collections. > >> > >> > > > > -- > > You received this message because you are subscribed to the Google > Groups "sqlalchemy" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to sqlalchemy+...@googlegroups.com . > > To post to this group, send email to > > sqlal...@googlegroups.com. > > > Visit this group at http://groups.google.com/group/sqlalchemy. > > For more options, visit https://groups.google.com/groups/opt_out. > > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] ORM events order
On Dec 5, 2013, at 12:14 PM, Tim Kersten wrote: > thank you. > > What of the relative ordering of the different ORM event types? i.e. > > before_flush > before_delete > after_flush > etc > > When looking at before_flush I see the before_delete has not yet been fired, > yet is has been fired in the after_flush. Is this guaranteed to always be the > case? yes, before_flush and after_flush provide boundaries around the mechanics of the flush itself. before_delete as well as the other mapper-level events like before_update before_insert after_update etc. are all within the flush mechanics. you can’t necessarily rely upon the ordering of insert/update/delete events within the flush however, relative to different objects and especially across different kinds of objects. The mapper-level flush events are fired right as individual batches of objects are being prepared for INSERT/UPDATE/DELETE statements. > > > On 5 Dec 2013, at 16:01, Michael Bayer wrote: > >> >> On Dec 5, 2013, at 10:51 AM, Tim Kersten wrote: >> >>> Hi Folks, >>> >>> Is the order ORM events ( >>> http://docs.sqlalchemy.org/en/rel_0_9/orm/events.html ) are fired in >>> deterministic and guaranteed to be the same every time? I've searched the >>> docs and google but couldn't anything relating to their relative order. >> >> >> the events are ordered. when you do an event.listen it appends the event >> listener to a list of listeners. the events are fired from the beginning >> of the list on forward.there’s actually an undocumented argument to >> event.listen() “insert=True” that will cause the listener to be inserted at >> position zero rather than appended. >> >> the reason the order of events is not really mentioned much is because >> there’s complex cases where the order of listener application has not been >> evaluated or tested. When you make use of mapper or instrumentation events >> against un-mapped base classes and such, the actual append() operation >> doesn’t occur until later, when classes are actually mapped, and this works >> by shuttling the event listener functions around to those classes. In these >> cases we don’t as yet have guarantees in place as to the order of the >> listeners being first applied, e.g. if you had a class that is a product of >> two mixins, and each mixin has listeners applied to it, that sort of thing. >> >> however, the order of listeners once applied should definitely be the same >> each time assuming no changes to the listener collections. >> >> > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To post to this group, send email to sqlalchemy@googlegroups.com. > Visit this group at http://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/groups/opt_out. signature.asc Description: Message signed with OpenPGP using GPGMail
Re: [sqlalchemy] ORM events order
thank you. What of the relative ordering of the different ORM event types? i.e. before_flush before_delete after_flush etc When looking at before_flush I see the before_delete has not yet been fired, yet is has been fired in the after_flush. Is this guaranteed to always be the case? On 5 Dec 2013, at 16:01, Michael Bayer wrote: > > On Dec 5, 2013, at 10:51 AM, Tim Kersten wrote: > >> Hi Folks, >> >> Is the order ORM events ( >> http://docs.sqlalchemy.org/en/rel_0_9/orm/events.html ) are fired in >> deterministic and guaranteed to be the same every time? I've searched the >> docs and google but couldn't anything relating to their relative order. > > > the events are ordered. when you do an event.listen it appends the event > listener to a list of listeners. the events are fired from the beginning of > the list on forward.there’s actually an undocumented argument to > event.listen() “insert=True” that will cause the listener to be inserted at > position zero rather than appended. > > the reason the order of events is not really mentioned much is because > there’s complex cases where the order of listener application has not been > evaluated or tested. When you make use of mapper or instrumentation events > against un-mapped base classes and such, the actual append() operation > doesn’t occur until later, when classes are actually mapped, and this works > by shuttling the event listener functions around to those classes. In these > cases we don’t as yet have guarantees in place as to the order of the > listeners being first applied, e.g. if you had a class that is a product of > two mixins, and each mixin has listeners applied to it, that sort of thing. > > however, the order of listeners once applied should definitely be the same > each time assuming no changes to the listener collections. > > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/groups/opt_out.
Re: [sqlalchemy] ORM events order
On Dec 5, 2013, at 10:51 AM, Tim Kersten wrote: > Hi Folks, > > Is the order ORM events ( > http://docs.sqlalchemy.org/en/rel_0_9/orm/events.html ) are fired in > deterministic and guaranteed to be the same every time? I've searched the > docs and google but couldn't anything relating to their relative order. the events are ordered. when you do an event.listen it appends the event listener to a list of listeners. the events are fired from the beginning of the list on forward.there’s actually an undocumented argument to event.listen() “insert=True” that will cause the listener to be inserted at position zero rather than appended. the reason the order of events is not really mentioned much is because there’s complex cases where the order of listener application has not been evaluated or tested. When you make use of mapper or instrumentation events against un-mapped base classes and such, the actual append() operation doesn’t occur until later, when classes are actually mapped, and this works by shuttling the event listener functions around to those classes. In these cases we don’t as yet have guarantees in place as to the order of the listeners being first applied, e.g. if you had a class that is a product of two mixins, and each mixin has listeners applied to it, that sort of thing. however, the order of listeners once applied should definitely be the same each time assuming no changes to the listener collections. signature.asc Description: Message signed with OpenPGP using GPGMail
[sqlalchemy] ORM events order
Hi Folks, Is the order ORM events ( http://docs.sqlalchemy.org/en/rel_0_9/orm/events.html ) are fired in deterministic and guaranteed to be the same every time? I've searched the docs and google but couldn't anything relating to their relative order. Cheers, Tim -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/groups/opt_out.
