On Wed, 26 Dec 2001 00:30:40 -0500, Edmund Lian wrote:
>I'm wondering how MiddleKit users are dealing with the issue of
>transactions. As far as I can tell, the notion of commits and
>rollbacks are
>not fully implemented in ObjectStore.py--methods like
>revertChanges(self)
>raise NotImplemented errors).
>
>Why I ask is because I'm used to the traditional RDBMS notions of
>transactions (and ACIDity) and not at all used to using an
>object-relational layer. I think that there might be situations
>where one
>wants to commit several objects to persistant storage atomically, but
>without support for transactions in MiddleKit (or MySQL for that
>matter),
>how does everybody cope? Do you really drop down to unwinding your
>..saveChanges() method calls by hand (i.e., with code)? Isn't this a
>bit
>icky?
Tip: If you want to have very simple MK/MySQL support of transactions you can
do like this (at least it works for me :-).
1) Subclass MySQLObjectStore and override saveChanges:
class MyMySQLObjectStore(MySQLObjectStore):
def saveChanges(self):
self.executeSQL('BEGIN')
try:
MySQLObjectStore.saveChanges(self)
except Exception, e:
self.executeSQL('ROLLBACK')
raise e
else:
self.executeSQL('COMMIT')
2) Make sure that your MySQL server supports transactions, i.e install InnoDB.
You don't need 4.0 to do this, a recent 3.23 is OK. The prebuilt Windows
binaries already have InnoDB installed but on Linux you may have to install
it separately. Read more about this on http://www.mysql.com/.
3) Edit GeneratedSQL/Create.sql and add TYPE=InnoDB after every create table:
create table MyClass (
myClassId int not null primary key auto_increment,
) TYPE=InnoDB;
The last step must be repeated every time you generate your SQL files from
the object model :-(
But if we ask Chuck kindly he might fix this in the MK generate stuff :-).
It would be perfect if one could set an option in Settings.config, like
'MySQLTableType':'InnoDB'.
/Stefan
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