Thank you very much for such a quick answer, Matrin, i'll do some research on it.
среда, 31 января 2018 г., 20:44:51 UTC+3 пользователь Martin Marrese написал: > > Hi Stanislav, > > Perhaps a way to avoid using `save` and `add_new` custom methods is to > rely on listeners, perhaps `after_update` and `after_insert` will let you > create historical records in some place else. > > A couple of years ago I achieved this with SQLAlchemy Continuum (1), but > I'm not sure in which state is that project now. > > You can also check these recipes (2) to see if any of those fit your > specific needs. > > Bests, > Martín > > 1- https://github.com/kvesteri/sqlalchemy-continuum > 2- > http://docs.sqlalchemy.org/en/latest/orm/examples.html?highlight=history#versioning-objects > > On Wed, Jan 31, 2018 at 2:27 PM Stanislav Lobanov <n101...@gmail.com > <javascript:>> wrote: > >> Hello, i need to create a system, that can store historical versions of >> objects. >> >> Example model looks like: >> >> class User(Base): >> id=Column(Integer) # ForeignKey >> start=Column(DateTime) >> end=Column(DateTime) >> name=Column(String) >> >> I have implemented .add_new() and .save() methods on base class, which >> performs custom logic on inserting rows into database. >> >> .add_new() method just assigns next id, default start and end date values >> (start=datetime.now() and end=None). >> >> Rows where start has value and end is null are considered "live" rows, >> all other rows are considered as "historical" >> >> .save() method changes current record dates (end date becomes current >> moment, so this version is considered as "historical", because it has start >> and end date lifetime moments set). Also, it performs some custom logic on >> determining if new version of record should be created — it should not be >> created, if name is not chaged. >> >> Example: >> >> user = User(name='User1') >> user.add_new() >> # user has values: id=1, start=<current datetime>, end=None, name='User1' >> >> user.name='test2' >> user.save() >> # user has values: id=1, start=<previous start>, end=<current datetime>, >> name='test2' >> >> user.name='test2' >> user.save() >> # user has values: id=1, start=<previous start>, end=<current datetime>, >> name='test2' and no insert performed, because name is not changed. >> >> >> >> This methods look for me inconsistent and error prone, so i want to be >> able to use session.add() method. >> >> Are there any possibility to add support for custom process of saving and >> modifying objects by using default sqlalchemy's apis? >> >> P.S.: in current example, table has composite pk (id, start, end), so id >> is not auto incremented when inserting new row. Also, in such scenario we >> can not have ForeignKey constraint. >> >> Thanks. >> >> -- >> SQLAlchemy - >> The Python SQL Toolkit and Object Relational Mapper >> >> http://www.sqlalchemy.org/ >> >> To post example code, please provide an MCVE: Minimal, Complete, and >> Verifiable Example. See http://stackoverflow.com/help/mcve for a full >> description. >> --- >> 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 <javascript:>. >> To post to this group, send email to sqlal...@googlegroups.com >> <javascript:>. >> Visit this group at https://groups.google.com/group/sqlalchemy. >> For more options, visit https://groups.google.com/d/optout. >> > -- > Martín > +54 911 5112 9448 > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- 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 https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
