Re: [HACKERS] Re: 9.4.1 -> 9.4.2 problem: could not access status of transaction 1

Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> writes:
> On Fri, May 29, 2015 at 11:24 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> B. We need to change find_multixact_start() to fail softly.

> Here is an experimental WIP patch that changes StartupMultiXact and
> SetMultiXactIdLimit to find the oldest multixact that exists on disk
> (by scanning the directory), and uses that if it is more recent than
> the oldestMultiXactId from shmem,

Not sure about the details of this patch, but I was planning to propose
what I think is the same thing: the way to make find_multixact_start()
fail softly is to have it find the oldest actually existing file if the
one that should be there isn't.

This would preserve the idea that we aren't trusting the multixact
tracking data to be completely right, which was the point of 78db307bb
and which evidently is still essential. It would also obviate the need
for other places to contain similar logic.

regards, tom lane