Josh Berkus wrote:
> Folks:
>
> I'm getting deadlock errors on one of the operations on my web
> application. It's a function which adds a large number of rows to a
> holding table, then updates that set of rows multiple times in order to
> present scoring information to the user.
>
> However, the function is deadlocking itself once it's in heavy use. I
> though that MVCC was supposed to supercede deadlocks, unless I
> specifically set locks, which I'm not.
>
> Help, anyone?
You must have misunderstood something. MVCC does not supersede deadlocks, nor can it prevent them. All
MVCC does is to help "readers" not beeing blocked by "writers" and vice versa, by avoiding the need for shared
"read" locks. But writers still need locks, so if your application does something like
Xact-1: Starts transaction Xact-2: Starts transaction Xact-1: Updates row A Xact-2: Updates
rowB Xact-1: Wants to update row B (blocks) Xact-2: Wants to update row A
then it's a deadlock. A deadlock is a deadlock and remains to be a deadlock, no matter if you have versioning or
not.
Jan
--
#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me. #
#================================================== JanWieck@Yahoo.com #
_________________________________________________________
Do You Yahoo!?
Get your free @yahoo.com address at http://mail.yahoo.com
