I wrote:
> What that'd have to imply is that get_ps_display() messed up,
> returning a bad pointer or a bad length.
> A platform-specific problem in get_ps_display() seems plausible
> enough. The apparent connection to a concurrent VACUUM FULL seems
> pretty hard to explain that way ... but maybe that's a mirage.
If I understand correctly that you're only seeing this in v13 and
HEAD, then it seems like bf68b79e5 (Refactor ps_status.c API)
deserves a hard look.
regards, tom lane