Re: Patch: Write Amplification Reduction Method (WARM)

On Thu, Mar 23, 2017 at 2:47 PM, Pavan Deolasee
<pavan.deolasee@gmail.com> wrote:
> It's quite hard to say that until we see many more benchmarks. As author of
> the patch, I might have got repetitive with my benchmarks. But I've seen
> over 50% improvement in TPS even without chain conversion (6 indexes on a 12
> column table test).

This seems quite mystifying.  What can account for such a large
performance difference in such a pessimal scenario?  It seems to me
that without chain conversion, WARM can only apply to each row once
and therefore no sustained performance improvement should be possible
-- unless rows are regularly being moved to new blocks, in which case
those updates would "reset" the ability to again perform an update.
However, one would hope that most updates get done within a single
block, so that the row-moves-to-new-block case wouldn't happen very
often.

I'm perplexed.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company