Re: [HACKERS] Patch: Write Amplification Reduction Method (WARM)

On Tue, Jan 31, 2017 at 04:52:39PM +0530, Pavan Deolasee wrote:
> The other critical bug I found, which unfortunately exists in the master too,
> is the index corruption during CIC. The patch includes the same fix that I've
> proposed on the other thread. With these changes, WARM stress is running fine
> for last 24 hours on a decently powerful box. Multiple CREATE/DROP INDEX cycles
> and updates via different indexed columns, with a mix of FOR SHARE/UPDATE and
> rollbacks did not produce any consistency issues. A side note: while
> performance measurement wasn't a goal of stress tests, WARM has done about 67%
> more transaction than master in 24 hour period (95M in master vs 156M in WARM
> to be precise on a 30GB table including indexes). I believe the numbers would
> be far better had the test not dropping and recreating the indexes, thus
> effectively cleaning up all index bloats. Also the table is small enough to fit
> in the shared buffers. I'll rerun these tests with much larger scale factor and
> without dropping indexes.

Thanks for setting up the test harness.  I know it is hard but
in this case it has found an existing bug and given good performance
numbers.  :-)

I have what might be a supid question.  As I remember, WARM only allows
a single index-column change in the chain.  Why are you seeing such a
large performance improvement?  I would have thought it would be that
high if we allowed an unlimited number of index changes in the chain.

--  Bruce Momjian          http://momjian.us EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +