Csaba Nagy wrote:
On Fri, 2007-02-02 at 10:51, Simon Riggs wrote:
Why do we need a SHARE lock at all, on the **referenc(ed)** table?

Well, here we do have a patch (deployed on production servers) which
does not put the shared lock on the referenced table, and it lets in
occasionally rows in the referencing tables which do not have parent
rows in the referenced table. I'm not sure what is the mechanism, but it
does happen, I can assure you. It happens rare enough that is not
disturbing for us, compared to the deadlocks which happen without the
patch - that's another matter...

You say below the cut that you're not updating keys, so presumably it's other columns. Which leads me to something I've wondered for a while - why do we lock the whole row? Is it just a matter of "not optimised that yet" or is there a good reason why locking just some columns isn't practical.

  Richard Huxton
  Archonet Ltd

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