Re: Memory Accounting

Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> writes:
> On Fri, Oct 04, 2019 at 12:36:01AM -0400, Tom Lane wrote:
>> What I think is happening is that c477f3e449 allowed this bit in
>> AllocSetRealloc:
>> context->mem_allocated += blksize - oldblksize;
>> to be executed in situations where blksize < oldblksize, where before
>> that was not possible.
>> ...
>> (I'm not quite sure why we're not seeing this failure on *all* the
>> 32-bit machines; maybe there's some other factor involved?)

> Interesting failure mode (especially that it does *not* fail on some
> 32-bit machines).

Just to make things even more mysterious, prairiedog finally showed
the Assert failure on its fourth run with c477f3e449 included:

https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=prairiedog&dt=2019-10-04%2012%3A35%3A41

It's also now apparent that lapwing and locust were failing only
sometimes, as well. I totally don't understand why that failure
would've been only partially reproducible. Maybe we should dig
a bit harder, rather than just deciding that we fixed it.

regards, tom lane