Tom Lane wrote:
Emmanuel Cecchet <m...@frogthinker.org> writes:
Tom Lane wrote:
True, but the problem is that the tuple might still be live to (some
snapshots in) that transaction, so we can't inject a duplicate tuple
without risking confusing it. In this particular case that isn't an
issue because the transaction is done executing, but the tqual.c
rules don't know that.
Please excuse my ignorance. I am not sure to get how the tuple could
still be live to some snapshots after the transaction has prepared.
Well, it couldn't be because there are no snapshots in that transaction
anymore. The problem is that the *other* transaction doesn't have a
good way to know that. It just sees an open transaction with
conflicting unique-index changes.
But when the transaction prepares, we know that. What would prevent us
to do at prepare time the same cleanup that commit does?
regards, manu (indentation (C) tom lane)
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