PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> EDT [767490] LOG: background worker "parallel worker" (PID 767794) was
> terminated by signal 9: Killed
You need to prevent the OOM killer from acting.
https://www.postgresql.org/docs/current/kernel-resources.html#LINUX-MEMORY-OVERCOMMIT
regards, tom lane