Simon Riggs wrote:
Rather than signalling, we could use a hasconflict boolean for each proc
in a shared data structure. It can be read without spinlock, but should
only be written while holding spinlock.
Each time we read a block we check if hasconflict is set. If it is, we
grab spinlock, recheck if it is set, if so read the conflict details,
clear the flag and drop the spinlock.
Yeah, that seems workable.
The aim of this type of conflict resolution was to reduce the footprint
of users that would be effected and defer it as much as possible. We've
spent time getting the latestCompletedXid, but we know deriving that
value is very difficult in the btree case at least. So what I would like
to do is pass the relid of a conflict across as well and use that to
reduce the footprint, now that we are performing the test inside the
buffer manager.
I agree that would be useful, but I'd prefer to keep it simple for now...
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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