FYI...I found this interesting. >Date: Sun, 17 Jun 2001 17:46:54 -0400 (EDT) >From: Andy Dustman <[EMAIL PROTECTED]> >Sender: <[EMAIL PROTECTED]> >To: Chuck Esterbrook <[EMAIL PROTECTED]> >Subject: Re: MySQLdb module: threadsafety went down? >Copyright: 2001 by Andy Dustman > >On Sun, 17 Jun 2001, Chuck Esterbrook wrote: > > > threadsafety used to be 2, but is now 1, meaning threads can no longer > > share a connection. > > > > What was the reason for the decrement? Were the previous versions buggy > > with 2? Or did the new version change such that 2 was no longer feasible? > >There was too much locking code required to do it correctly, and I think >sharing connections is a bad idea in the first place. If you know what >you're doing, you can wrap connections with a mutex. This is effectively >what happens, for example, in Zope. > >I actually enhanced the locking mechanism somewhat in the not-released >0.3.6. That's what convinced me it should be taken out. The two things >which together make it nearly intractable are: > >a) mysql_store_result() vs. mysql_use_result(). With the former, all rows >are transferred to the client all at once, and sharing the connection is >easy. With the latter, rows are transferred with each mysql_fetch_row() >call, and you must fetch all the rows prior to starting another query. >Thus the connection lock has to be held until the last row is read. This >lock was managed by their respective cursor mixins. > >b) Transactions: If they are enabled, you cannot safely share the >connection from the time a transaction begins until the time it is >committed or rolled back. (I doubt most situations would call for multiple >threads engaging in the same transaction.) This requires an additional >lock, acquired by the cursor but released by the connection object, which >implements commit/rollback. > >Combine both of those, and it's a big mess. Better off not to share >connections in the first place. It makes the code much simpler. > >-- >Andy Dustman PGP: 0xC72F3F1D > @ .net http://dustman.net/andy >"I'd rather listen to Newton than to Mundie. He may have been dead for almost >three hundred years, but despite that he stinks up the room less." -- >Linus T. _______________________________________________ Webware-discuss mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/webware-discuss
