Re: allowing wal_level change at run time

On 8/18/15 8:48 AM, Robert Haas wrote:
> On Tue, Aug 18, 2015 at 7:59 AM, Peter Eisentraut <peter_e@gmx.net> wrote:
>> How would we handle decreases at run time?  We can prevent >=archive ->
>> minimal if archiving is running or there are physical replication slots,
>> and we can prevent logical -> something less if there are logical
>> replication slots, but AFAICT, we don't have a way to check whether
>> anyone currently needs level hot_standby.
> 
> What do you mean by "prevent"?  If the user edits postgresql.conf and
> reduces the setting, and then reloads the configuration file, they
> have a right to expect that the changes got applied.

We have certain checks in place that require a minimum wal_level before
other things are allowed.  For example, turning on archiving requires
wal_level >= archive.  The issue is then, if you have archiving on and
then turn wal_level to minimal at run time, we need to prevent that to
preserve the integrity of the original check.