Re: Replication/backup defaults

On 2 January 2017 at 09:48, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:

> I'm willing to assist in a project to allow changing wal_level online
> in this release. Please let's follow that path.

wal_level looks like one of the easier ones to change without a server restart

There are actions to take in either direction, up or down. My initial
thoughts on the pseudocode would be...

reset wal_level so all new transactions see that value
/* actions after setting new value */
if (old_wal_level < new_wal_level) /* going up */
get list of running transactions (perhaps only those using no-WAL-opt)
else /* coming down */
{
if (old_wal_level == logical)
disconnect logical replication and disallow logical slots
if (new_wal_level == minimal)
disconnect streaming replication and disallow physical slots
}
wait for a checkpoint (fast checkpoint if no other transactions actions active)
if (list)
wait for list of running xacts to complete
wait for a checkpoint (fast checkpoint if no other transactions actions active)
XLogReportParameters()

So it looks easier to go up than down, which is good since that is the
important direction.

--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services