Re: [sqlalchemy] How-to : update A also create an update of B
Le jeudi 30 août 2012 17:16:40 UTC+2, Michael Bayer a écrit : def after_flush(session, flush_context): my_bs = figure_out_bs(session) new_session = Session(bind=session.connection()) new_session.add_all(my_bs) # this won't actually COMMIT the transaction as we are # already inside one new_session.commit() As I'm not the only developer for this application, I can't use pure SQL commands. I've tried the after_flush solution. It works. What could be the problem to use setter ? For example Class A has attribut family_id @family_id.setter def family_id(self, family_id): self._family_id = family_id update_linked_entities_with_family(family_id) with update_linked_entities_with_family a function that grab and modify Bs. You point that it could be used only for changing Python attributs. I use it to change SQLAlchemy entities and fields. What could be the drawback of this solution ? -- 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/-/h11OiMXCyloJ. 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.
[sqlalchemy] How-to : update A also create an update of B
Hi there ! I'm going mad looking for a solution for what seems a simple problem. When object A is updated, I also want object B to be updated, using some computation based on A new values. From now, I can detect when A is modified using after_update. What I try is to look at event Session.after_flush, if in Session.dirty there is an instance of A, I call the update of B. Within after_flush I can see Session.dirty with the modified B. But no SQL UPDATE is issued at all. Any tip for me ? -- 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/-/d2bO9dVrSpUJ. 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.
[sqlalchemy] Re: How-to : update A also create an update of B
A friend point me out the hybrid_property and the fact I can detect an update of A fields before doing the commit, issuing some update for B. I'll try this idea. -- 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/-/F_Y-ZW4hpIIJ. 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.
Re: [sqlalchemy] How-to : update A also create an update of B
Only if some computation based on A new values means that there are SQL-level functions which you need to get at, does the rationale for after_update/after_flush events to come up.Unfortunately you can't emit a flush() within any of these events, as they are already local to the flush() call itself.Nor can you change the state of the Session within any of the after_ events, as the Session is already doing its work. You can add new state to the Session within the after_flush_postexec() method, however you'd need to call flush() again for those changes to be flushed. The computation will modify B, which is also a map of a table. So the options: 1. if some computation is only in-Python computation, and *not* SQL functions, then set the state of B within object-level events, such as the __init__() of A, a @property on A, @validates events on A, or attribute events on A. I've used something like this : A has field family_id, which trigger the modification of B (and not anly B, but also some more tables) @family_id.setter def family_id(self, family_id): self._family_id = family_id self.update_linked_entities_with_family(family_id) Then at session.commit(), A is updated, but also the other linked entities. This works. But it's not really nice, because any changes, even rollbacked one will call the update_linked_entitites method. 2.if some computation involves SQL functions: a. emit your modifications to B using only SQL statements and Session.execute(), not by adding any new state to the Session or re-flushing. b. pre-execute your SQL functions for A *outside* of the flush, then apply values to B as needed. c. use a second Session inside the event: def after_flush(session, flush_context): my_bs = figure_out_bs(session) new_session = Session(bind=session.connection()) new_session.add_all(my_bs) # this won't actually COMMIT the transaction as we are # already inside one new_session.commit() I can read this, but I don't understand how to do this and not exactly how it works. It is 3 solutions right , not 3 points I have to go through ? Step A : calling only Session.execute will output direct SQL commands, thus not modify the Session dirty list and the state. Seems quiet easy but less readable because of the direct SQL commands. Step B : what *outside* of the flush means ? Step C : I will try this one because it seems nice, using Session/transaction. Thank you for the explanation. I have a lot to do to fully understand SQLAlchemy. -- 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/-/DuspcAQVczsJ. 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.
[sqlalchemy] Re: Table name without quoting with upper case
On 25 nov, 16:28, Michael Bayer mike...@zzzcomputing.com wrote: I did a little googling and Sybase can handle the quotes, if you set set quoted_identifier on on your database. (http://manuals.sybase.com/onlinebooks/group-as/asg1250e/sqlug/@ebt-li...) Yep ! That's kind of solution, also setting this in the sybase engine cause some other kind of problems with some tables with very weird definition (but until I use them, it's not an issue) Which leaves us at the only answer you'll likely care about, just set quote=False on your Table object. Good luck ! Nice ! I have found the quote attribut of the Table class in the SA doc, try it and it's all good. Now I just have to put it in the right place in my pylons files (which is not hard to do : at the end of the model file where the class is defined). Thanks a lot for this quick answer. Tony -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@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.
[sqlalchemy] Table name without quoting with upper case
Hi there ! I'm a newby du SA and try to make it work with our production platform, using Sybase and old and scarry database schema, with table names like Prestation , with 1 upper case. Sybase does not allow (to my knowledge) tu use something like select Prestation.id So I try to figure how to avoid the quoting of the tablename. I know, I read that if tablename is not lower case, it's quoted. But I can't afford it. I'm drilling into SA to find where the quoting is done (looking in schema.py at the moment). But if somebody can point me to a prettier solution than adding my piece of crap code for this case, it would be great ! Tony PS : platform Sybase ASE 15.5 SQLAlchemy 0.6.5 with pyodbc over FreeTDS/Fedora -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@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.
