On Tue, Feb 3, 2015 at 1:43 PM, Andres Freund <and...@2ndquadrant.com> wrote:
> Hi, > > I think these days there's no reason for the split between the archive > and hot_standby wal levels. The split was made out of volume and > stability concerns. I think we can by now be confident about the > wal_level = hot_standby changes (note I'm not proposing hot_standby = > on). > > So let's remove the split. It just gives users choice between two options > that don't have a meaningful difference. > +1. Additionally I think we should change the default for wal_level to > hot_standby and max_wal_senders (maybe to 5). That way users can use > pg_basebackup and setup streaming standbys without having to restart the > primary. I think that'd be a important step in making setup easier. > Yes, please! Those who want to optimize their WAL size can set it back to minimal, but let's make the default the one that makes life *easy* for people. The other option, which would be more complicated (I have a semi-finished patch that I never got time to clean up) would be for pg_basebackup to be able to dynamically raise the value of wal_level during it's run. It would not help with the streaming standby part, but it would help with pg_basebackup. That could be useful independent - for those who prefer using wal_level=minimal and also pg_basebackup.. Previously there have been arguments against changing the default of > wal_level because it'd mean the regression tests wouldn't exercise > minimal anymore. That might be true, but then right now we just don't > exercise the more complex levels. If we're really concerned we can just > force a different value during the tests, just as we do for prepared > xacts. > Seems we should focus our tests on the stuff that people actually use in reality? :) And if we change the default, then even more people will use that level. But it would definitely be a good idea to have some buildfarm animals set up to test each one. Comments? > > Additionally, more complex and further into the future, I wonder if we > couldn't also get rid of wal_level = logical by automatically switching > to it whenever logical slots are active. > If it can be safely done online, I definitely think that would be a good goal to have. If we could do the same for hot_standby if you had physical slots, that might also be a good idea? -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/
