Wow thank you for the description, that helps me clear up alot of confusion I was having :)
-Thadeus On Mon, Jan 4, 2010 at 8:12 PM, mdipierro <mdipie...@cs.depaul.edu> wrote: > This is a very point. I will add it to the manual. > > Massimo > > On Jan 4, 6:53 pm, Michael Toomim <too...@gmail.com> wrote: >> I just figured out why transactions were confusing me and would like >> to share. >> >> The default for postgresql makes every statement its own transaction >> unless you issue "BEGIN TRANSACTION", in which case nothing commits >> until you issue "COMMIT". This is called "autocommit" mode in >> postgresql, because each statement is automatically committed unless >> it is in a transaction. This goes AGAINST the sql92 standard, so you >> can turn it off with "\set autocommit off". >> >> In web2py, "automatic commits" actually means the opposite. web2py >> follows the SQL standard, where you never need to issue "BEGIN" (it is >> implicit before every query) and nothing commits until you issue >> "COMMIT". On top of that, web2py automatically issues "COMMIT" for >> you after every controller function exits, unless it throws an error, >> in which case it issues a ROLLBACK. >> >> So the confusing part for me is that postgresql has a completely >> different type of "autocommit" mode, and that transactions work >> opposite of the default in postgres. It might help future users to >> add a line to the end of the "commit and rollback" section in the >> manual that says something like "Note that web2py has no explicit >> BEGIN TRANSACTION statement which PostgreSQL users may be accustomed >> to. Web2Py uses the equivalent of "\set AUTOCOMMIT OFF" as described >> athttp://www.postgresql.org/docs/8.4/interactive/app-psql.html."; >> >> Massimo, what would you think of adding this to the manual? >> >> On Jan 4, 12:56 pm, mdipierro <mdipie...@cs.depaul.edu> wrote: >> >> > On Jan 4, 1:54 pm, Thadeus Burgess <thade...@thadeusb.com> wrote: >> >> > > Can you disable auto_commit so that you have to explicitly declare >> > > db.commit() ? >> >> > You can already expliticely db.commit() >> >> > > Also, say I have the following >> >> > > db.table.insert(myfields=...) >> >> > > and then later in the same request, would a >> >> > > db.table.select() pull in the newly inserted record, or does the >> > > record need to be committed first? >> >> > It will show even if you do not commit >> >> > > If I insert data in a long running request, and then another request >> > > comes in that is opened in another thread, does it have access to any >> > > uncommitted data from the other running threads? >> >> > No unless you db.commit() after each insert (and you should if the >> > process is long running or it may lock the database). >> >> > > -Thadeus >> >> > > On Sun, Dec 27, 2009 at 3:51 PM, mdipierro <mdipie...@cs.depaul.edu> >> > > wrote: >> > > > a request arrives web2py creates a new database connection object >> > > > or pools an existing connection from a connection pool, then it >> > > > creates a cursor object. All db IO in the request is done via the >> > > > cursor object. This is thread-safe in the sense that the cursor is >> > > > only used in one thread. As soon as the request completes, the >> > > > transaction is committed or rolled back and the connection is closed >> > > > or recycled. >> >> > > > You can pass the db object to a thread and use it in another thread >> > > > BUT you must make sure that t >> >> > > -- > > You received this message because you are subscribed to the Google Groups > "web2py-users" group. > To post to this group, send email to web...@googlegroups.com. > To unsubscribe from this group, send email to > web2py+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/web2py?hl=en. > > > -- You received this message because you are subscribed to the Google Groups "web2py-users" group. To post to this group, send email to web...@googlegroups.com. To unsubscribe from this group, send email to web2py+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/web2py?hl=en.
