Re: Performance Improvement by reducing WAL for Update Operation

On Tuesday, July 09, 2013 2:52 AM Mike Blackwell wrote:

> I can't comment on further direction for the patch, but since it was marked as Needs Review in the CF app I took a quick look at it.
Thanks for looking into it.

Last time Heikki has found test scenario's where the original patch was not performing good.
He has also proposed a different approach for WAL encoding and sent the modified patch which has comparatively less negative performance impact and
asked to check if the patch can reduce the performance impact for the scenario's mentioned by him.
After that I found that with some modification's (use new tuple data for encoding) in his approach, it eliminates the negative performance impact and
have WAL reduction for more number of cases.

I think the first thing to verify is whether the results posted can be validated in some other environment setup by another person.
The testcase used is posted at below link:
http://www.postgresql.org/message-id/51366323.8070606@vmware.com

> It patches and compiles clean against the current Git HEAD, and 'make check' runs successfully.

> Does it need documentation for the GUC variable 'wal_update_compression_ratio'?

This variable has been added to test the patch for different compression_ratio during development test.
It was not decided to have this variable permanently as part of this patch, so currently there is no documentation for it.
However if the decision comes out to be that it needs to be part of patch, then documentation for same can be updated.

With Regards,
Amit Kapila.