Re: allowing wal_level change at run time

On 8/18/15 12:35 PM, Robert Haas wrote:
> If archive_mode=on or max_wal_senders>0, then we need at least
> wal_level=archive.  Otherwise wal_level=minimal is enough.

Totally forgot about max_wal_senders.

However, the thread I linked to earlier aimed for a different master
plan (or if not, I'm aiming for it now).  There is camp 1, which wants
to keep all the defaults the same, for "performance" or something like
that.  And there is camp 2, which wants to have a replication-friendly
setup by default.  Instead of fighting over this, your idea was to be
able to switch between 1 and 2 easily (which means in particular without
restarts).

But if we tie the effective wal_level to archive_mode or
max_wal_senders, both of which are restart-only, then we haven't gained
anything.  (We would have removed half a GUC parameter, effectively.
Not bad, but not very exciting.)