Re: Reviewing freeze map code

On Tue, Jun 21, 2016 at 10:47 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Mon, Jun 20, 2016 at 5:59 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>>> Consider what happens if we, after restarting at l2, notice that we
>>> can't actually insert, but return in the !HeapTupleMayBeUpdated
>>> branch.
>
>> OK, I see what you mean. Still, that doesn't seem like such a
>> terrible cost. If you try to update a tuple and if it looks like you
>> can update it but then after TOASTing you find that the status of the
>> tuple has changed such that you can't update it after all, then you
>> might need to go set xmax = MyTxid() on all of the TOAST tuples you
>> created (whose CTIDs we could save someplace, so that it's just a
>> matter of finding them by CTID to kill them).
>
> ... and if you get an error or crash partway through that, what happens?

Then the transaction is aborted anyway, and we haven't leaked anything
because VACUUM will clean it up.

--
Robert Haas
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