PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> Thu, 18 Jun 2020 14:41:13 GMT The database process was killed by the OS due
> to excessive memory consumption. It is recommended to tune your database
> workload and/or parameter usage to reduce memory consumption.
This looks like you got hit by the dreaded OOM killer. See
https://www.postgresql.org/docs/current/kernel-resources.html#LINUX-MEMORY-OVERCOMMIT
for some background and advice.
regards, tom lane