On Fri, Sep 11, 2009 at 11:24 AM, mdipierro <[email protected]> wrote:
> > The new mechanism only kicks in if you have SQLITE and the references > are set as ondelete='CASCADE' (the default). > If you try to access a non sqlite database nothing changes > If you try to access an existing sqlite database, then set > oncascade='' and migrate=False. > I cannot think of a situation where this can create conflict. > If you have web2py doing "web2py cascade" on sqlite db named "a"; AND you have (something else) creating sqlite records, and does "cascade triggers" in sqlite db named "a" (co-accessed by web2py &, say, django) then you have trouble. I suggest this be re-implemented to do cascade the way sqlite suggests. (see http://www.sqlite.org/cvstrac/wiki?p=ForeignKeyTriggers ) > > On Sep 11, 11:18 am, Yarko Tymciurak <[email protected]> wrote: > > On Fri, Sep 11, 2009 at 1:42 AM, mdipierro <[email protected]> > wrote: > > > > > On Sep 11, 1:19 am, Richard <[email protected]> wrote: > > > > > on delete cascade in SQLite > > > > > > Fantastic! My feature request for this can be closed: > > >http://code.google.com/p/web2py/issues/detail?id=50 > > > > > Can you do it or should I do it? > > > > > > Did the solution involve sqlite triggers? > > > > > No. The solution is quite dumb. recursively delete all referencing > > > records. I guess it could be improved using triggers. > > > > Yes - I was going to mention this too when I saw it.... There is a > pattern > > on SQLite pages somewhere (I pointed someone to them once). > > > > My immediate concern is about web2py only activity taking care of an > > external db - and what is another app is cooperating on the DB (like we > are > > doing for PyCon - either web2py or django...)... > > > > What is the db exists, and already has triggers to handle cascade? What > > happens then? > > What is another application assumes / depends on the DB to have the > tirggers > > (so one - web2py - does the cascade action, but the other doesn't). > > > > Make sense? I think this > > needs more thought. > > > > - Yarko > > > > > > > > > > > row = db(db.mytable.id>0).select().first() > > > > > > very convenient > > > > > > Richard > > > > > > On Sep 11, 3:12 pm, mdipierro <[email protected]> wrote: > > > > > > > I have made some changes to the code in trunk: > > > > > > > 1) Since tonight I attended a presentation about how SQLAlchemy can > do > > > > > on delete cascade in SQLite even if SQLite does not support it, I > > > > > implemented this feature in web2py too. There is nothing you have > to > > > > > do it now there by default. For example: > > > > > > > db=DAL('sqlite://test.db') > > > > > db.define_table('a',Field('name')) > > > > > > db.define_table('b',Field('a',db.a,ondelete='CASCADE'),Field('name')) > > > > > db.a.insert(name='xxx1') > > > > > db.a.insert(name='xxx2') > > > > > db.a.insert(name='xxx3') > > > > > db.a.insert(name='xxx4') > > > > > db.b.insert(a=2,name='yyy1') #(1) > > > > > db.b.insert(a=2,name='yyy2') #(1) > > > > > db.b.insert(a=3,name='yyy3') > > > > > db(db.a.id==2).delete() > > > > > for row in db(db.b.a==2).select(): print row # prints nothing as it > > > > > should > > > > > > > Notice ondelete='CASCADE' is default. > > > > > > > 2) you can now do: > > > > > > > row = db(db.mytable.id>0).select().first() > > > > > row = db(db.mytable.id>0).select().last() > > > > > > > and row is None if no records are selected. > > > > > > > 3) I fixed the problem with the memory leak reported by zahariash > > > > > > > 4) I refactored some code in main.py, compileapp.py and globals.py. > > > > > This should make the code cleaner. Hopefully I did not break it. > > > > > Please give it a try. > > > > > > > Massimo > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "web2py-users" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/web2py?hl=en -~----------~----~----~----~------~----~------~--~---
