Re: pgsql: Fix WAL replay of locking an updated tuple

Tom Lane wrote:
> Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> > Fix WAL replay of locking an updated tuple
>
> The test added by this patch certainly looks like it's backwards.
> Shouldn't you be clearing HOT_UPDATED only if the tuple is *not*
> XMAX_IS_LOCKED_ONLY?
>
> If the code is actually correct as written, then I think that test
> macro is very unfortunately named.

I don't understand.  Note that this is about replaying a tuple lock
operation; if the tuple we're locking had been updated by another
transaction, then during the lock operation we don't want to touch
either HOT_UPDATED or t_ctid, because they contain values that are valid
per the pre-existing update.  We are assuming that those values are
correctly set prior to this xlog routine touching it (the replay of the
update must have already set them.)

--
Álvaro Herrera                http://www.2ndQuadrant.com/
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