Re: Redesigning checkpoint_segments

On 02/05/2015 01:28 PM, Robert Haas wrote:
> On Thu, Feb 5, 2015 at 2:11 PM, Josh Berkus <josh@agliodbs.com> wrote:
>> Except that, when setting up servers for customers, one thing I pretty
>> much always do for them is temporarily increase checkpoint_segments for
>> the initial data load.  So having Postgres do this automatically would
>> be a feature, not a bug.
> 
> Right!
> 
>> I say we go with ~~ 1GB.  That's an 8X increase over current default
>> size for the maximum
> 
> Sounds great.
> 
>> Default of 4 for min_wal_size?
> 
> I assume you mean 4 segments; why not 3 as currently?  As long as the
> system has the latitude to ratchet it up when needed, there seems to
> be little advantage to raising the minimum.  Of course I guess there
> must be some advantage or Heikki wouldn't have made it configurable,
> but I'd err on the side of keeping this one small.  Hopefully the
> system that automatically adjusts this is really smart, and a large
> min_wal_size is superfluous for most people.

Keep in mind that the current is actually 7, not three (3*2+1).  So 3
would be a siginficant decrease.  However, I don't feel strongly about
it either way.  I think that there is probably a minimum reasonable
value > 1, but I'm not sure what it is.

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com