Per-tablespace autovacuum settings

Hello,

Is there any interest in making autovacuum parameters available on a
tablespace level in order to apply those to all vacuumable objects in the
tablespace?

We have a set of tables running on ZFS, where autovacuum does almost no good
to us (except for preventing anti-wraparound) due to the nature of ZFS (FS
fragmentation caused by copy-on-write leads to sequential scans doing random
access) and the fact that our tables there are append-only. Initially, the
team in charge of the application just disabled autovacuum globally, but
that lead to a huge system catalog bloat.

At present, we have to re-enable autovacuum globally and then disable it
per-table using table storage parameters, but that is inelegant and requires
doing it once for existing tables and modifying the script that periodically
creates new ones (the whole system is a Postgres-based replacement of an
ElasticSearch cluster and we have to create new partitions regularly).

Grouping tables by tablespaces for the purpose of autovacuum configuration
seems natural, as tablespaces are often placed on another filesystems/device
that may require changing how often does autovacuum run, make it less/more
aggressive depending on the I/O performance or require disabling it
altogether as in my example above. Furthermore, given that we allow
cost-based options per-tablespace the infrastructure is already there and
the task is mostly to teach autovacuum to look at tablespaces in addition to
the relation storage options (in case of a conflict, relation options should
always take priority).

Regards,
Oleksii Kliukin