Re: Getting rid of wal_level=archive and default to hot_standby + wal_senders

On 2015-02-03 10:41:04 -0500, Tom Lane wrote:
> Andres Freund <andres@2ndquadrant.com> writes:
> > 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.
> 
> I always thought the reason for defaulting to "minimal" was performance.
> I'd like to see proof that the impact of wal_level = hot_standby is
> negligible before we consider doing this.

Well, it really depends on what you're doing. The cases where minimal is
beneficial is when you COPY into a table that's been created in the same
(sub)xact or rewrite it.. Other than that there's not really a
difference?

> The argument that having to change one more GUC is an undue burden while
> configuring hot standby seems ridiculous from here.  HS is not nearly
> "push the EASY button and you're done", and this change wouldn't make
> it so.

But pg_basebackup is pretty close to being that easy, isn't it? There's
still pg_hba.conf to deal with, but other than that...

And with a littlebit more work (safely autocreate replication slots, so
wal files aren't getting removed prematurely), we can make amke HS
simpler as well.

Greetings,

Andres Freund

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