Re: [sqlalchemy] Re: SQLAlchemy + Elixir + Tornado overall setup
Thanks Michael. On Fri, Feb 11, 2011 at 1:44 PM, Michael Bayer wrote: > > On Feb 11, 2011, at 3:05 PM, Romy wrote: > > > On Feb 11, 9:13 am, Michael Bayer wrote: > >> autocommit=True means every SELECT statement as well as every flush() > uses its own transaction, that begins as the method is called, and is > immediately closed, within the scope of the method call on your end. > begin() *only* works when autocommit=True, and only affects the way > SQLAlchemy pulls connections from the connection pool.DBAPI has no > "begin", the connection itself is always in a transaction as soon as > statements are emitted, unless commit() or rollback() is called. > > > > In the entire time I've been running autocommit=True (on myISAM), I've > > never seen SELECTs get their own transaction in the log output, while > > every UPDATE/INSERT does. Is there something wrong w/ the log output ? > > again, as far as the DBAPI is concerned, everything is "in a transaction", > the myISAM tables just ignore it.The COMMIT is emitted by SQLalchemy if > the statement within the autocommit execution was a DML (CRUD) statement. > See > http://www.sqlalchemy.org/docs/core/connections.html#understanding-autocommit(I'd > recommend reading the whole page as well as > http://www.sqlalchemy.org/docs/orm/session.html) > > > > > > -- > > 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. > > > > -- > 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. > > -- 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.
Re: [sqlalchemy] Re: Strange ObjectDeletedError
I never did understand the pros or cons of running autocommit=True, aside from this flushing issue. Are there performance implications ? On Mon, Feb 7, 2011 at 1:22 PM, Michael Bayer wrote: > I actually just did a little bit of reverse course on this in 0.7. I've > moved all the accounting into the try/except block so that the flush > completes fully before the autocommit expires everything. This is a change > to a pattern that's been the same way since 0.4 so hoping nothing bad happens > when we put 0.7 out into betas. > > > On Feb 7, 2011, at 2:52 PM, Romy Maxwell wrote: > >> Are there any downsides to setting expire_on_commit=False when using >> autocommit=True ? In other words, should I expect to see stale data or >> other side effects ? >> >> On Mon, Feb 7, 2011 at 8:30 AM, Michael Bayer >> wrote: >>> >>> On Feb 7, 2011, at 7:42 AM, Romy Maxwell wrote: >>> >>>> Hey Michael, >>>> >>>> I didn't wanna revive a really old thread >>>> [http://www.mail-archive.com/sqlalchemy@googlegroups.com/msg16598.html], >>>> so I figured maybe you won't mind the email. >>>> >>>> I don't understand why, in the thread, using autocommit=True makes the >>>> object unreachable, or what that actually means. I'm assuming it was >>>> referring to the latter part of the code: >>>> >>>>> o = s.query(T).get(2) >>>>> o.id = 10 >>>>> o.description = "Changed" >>>>> s.flush() >>>> >>>> With autocommit=True, I've always thought flushes created their own >>>> transactions, like so: >>>> >>>> s.begin() >>>> s.flush() >>>> s.commit() >>>> >>>> But if that was true, then the commit happens after the flush. How >>>> would the commit expire anything and/or make anything unreachable for >>>> the flush ? >>> >>> >>> The commit is expiring because that's what it does when expire_on_commit is >>> True. So the flush goes into its post-commit accounting, it in fact has >>> to reload all the objects, one at a time, so is hugely inefficient and I'm >>> going to add a big warning for that in 0.7, ticket 2041. >>> >>> >>> > > -- 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.
