Standby reads fail when autovacuum take AEL during truncation

[Adrien NAYRAT]

Hello hackers,

I was faced on $SUBJECT  on an heavily updated table and the same table 
heavily accessed on standby server.

I notice autovacuum try to take an AEL in lazy_truncate_heap(). On 
primary we try during VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL (50ms) and we 
failed after several attempts.

But we do not have this mechanism on a standby, AEL could lock simple 
SELECT during the RelationTruncate().

Please note, this can occurs even with hot_standby_feedback = on

I wonder how we can improve this? Maybe by introducing an option to 
disable truncation for autovacuum on specific table?

Thanks!