On Mon, Mar 12, 2012 at 9:24 PM, Noah Misch <noah@leadboat.com> wrote:
> When we lock an update-in-progress row, we walk the t_ctid chain and lock all
> descendant tuples. They may all have uncommitted xmins. This is essential to
> ensure that the final outcome of the updating transaction does not affect
> whether the locking transaction has its KEY SHARE lock. Similarly, when we
> update a previously-locked tuple, we copy any locks (always KEY SHARE locks)
> to the new version. That new tuple is both uncommitted and has locks, and we
> cannot easily sacrifice either property. Do you see a way to extend your
> scheme to cover these needs?
No, I think that sinks it. Good analysis.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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