Re: Performance Improvement by reducing WAL for Update Operation

On Tue, Feb  4, 2014 at 08:11:18PM +0100, Andres Freund wrote:
> On 2014-02-04 14:09:57 -0500, Bruce Momjian wrote:
> > On Tue, Feb  4, 2014 at 01:28:38PM -0500, Robert Haas wrote:
> > > Meanwhile, in friendlier cases, like "one short and one long field, no
> > > change", we're seeing big improvements.  That particular case shows a
> > > speedup of 21% and a WAL reduction of 36%.  That's a pretty big deal,
> > > and I think not unrepresentative of many real-world workloads.  Some
> > > might well do better, having either more or longer unchanged fields.
> > > Assuming that the logic isn't buggy, a point in need of further study,
> > > I'm starting to feel like we want to have this.  And I might even be
> > > tempted to remove the table-level off switch.
> > 
> > Does this feature relate to compression of WAL page images at all?
> 
> No.

I guess it bothers me we are working on compressing row change sets
while the majority(?) of WAL is page images.  I know we had a page image
compression patch that got stalled.

--  Bruce Momjian          http://momjian.us EnterpriseDB                             http://enterprisedb.com
 + Everyone has their own god. +