Re: ERROR: invalid memory alloc request size <a_big_number_here>

[Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>]

Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> I think the problem is that CreateMultiXactId calls
> GetNewMultiXactId and then RecordNewMultiXact, and the lock is released
> between the calls.  So one backend could try to read the offset before
> another one had the time to finish writing it.

Ugh, yes, that is clearly a hole :-( even if it turns out not to explain
Matteo's observation.

I don't see any easy way to fix this except by introducing a lot more
locking than is there now --- ie, holding the MultiXactGenLock until the
new mxact's starting offset has been written to disk.  Any better ideas?

			regards, tom lane