Re: problems with making relfilenodes 56-bits

On Wed, Oct 5, 2022 at 5:19 AM Andres Freund <andres(at)anarazel(dot)de> wrote:

>
> I light dusted off my old varint implementation from [1] and converted the
> RelFileLocator and BlockNumber from fixed width integers to varint ones. This
> isn't meant as a serious patch, but an experiment to see if this is a path
> worth pursuing.
>
> A run of installcheck in a cluster with autovacuum=off, full_page_writes=off
> (for increased reproducability) shows a decent saving:
>
> master: 241106544 - 230 MB
> varint: 227858640 - 217 MB
>
> The average record size goes from 102.7 to 95.7 bytes excluding the remaining
> FPIs, 118.1 to 111.0 including FPIs.
>

I have also executed my original test after applying these patches on
top of the 56 bit relfilenode patch. So earlier we saw the WAL size
increased by 11% (66199.09375 kB to 73906.984375 kB) and after this
patch now the WAL generated is 58179.2265625. That means in this
particular example this patch is reducing the WAL size by 12% even
with the 56 bit relfilenode patch.

[1] https://www.postgresql.org/message-id/CAFiTN-uut%2B04AdwvBY_oK_jLvMkwXUpDJj5mXg--nek%2BucApPQ%40mail.gmail.com

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com