wambacher@posteo.de writes:
> this morning my database crashed, because of a problem during autovacuum.
> this is the second time during the last 2 month and i can't find out why.
Can you get a stack trace from the crash?
https://wiki.postgresql.org/wiki/Generating_a_stack_trace_of_a_PostgreSQL_backend
The evidence may be gone by now for your current crash, but if so, make
sure you are prepared to capture info from the next one.
The other respondent might be right that this ultimately traces to
data corruption, but it's hard to be sure without more info.
regards, tom lane