Re: PG17 optimizations to vacuum

On 03/09/2024 10:34, Pavel Luzanov wrote:
> On 03.09.2024 00:11, Heikki Linnakangas wrote:
>> Pavel, did you test v17 with checksums enabled and v16 with checksums
>> disabled, by any chance?
>
> Exactly, You are right!
>
> My v16 cluster comes from the default Ubuntu distribution.
> I forgot that checksums disabled by default.
> But when I initialize the master cluster, I automatically set -k option.
>
> More accurate results for the test:
>
> CREATE TABLE t(id integer) WITH (autovacuum_enabled = off);
> INSERT INTO t SELECT gen.id FROM generate_series(1,3_500_000) gen(id);
> VACUUM FREEZE t;
> UPDATE t SET id = id + 1;
> VACUUM FREEZE VERBOSE t;
>
> checksums disabled
> v16.4 WAL usage: 77437 records, 20832 full page images, 110654467 bytes
> master WAL usage: 61949 records, 20581 full page images, 92549229 bytes
>
> checksums enabled
> v16.4 WAL usage: 92848 records, 20985 full page images, 194863720 bytes
> master WAL usage: 76520 records, 20358 full page images, 181867154 bytes

That's more like it :-)

> This a great optimization!
>
> Peter, Melanie, Heikki,
> Thank you very much for your help and time spent!
> Sorry for the noise before the release of PG17.

Thanks for the testing!

--
Heikki Linnakangas
Neon (https://neon.tech)