Re: [HACKERS] Vacuum: allow usage of more than 1GB of work mem

On Thu, Jan 19, 2017 at 6:33 AM, Anastasia Lubennikova
 wrote:
> 28.12.2016 23:43, Claudio Freire:
>
> Attached v4 patches with the requested fixes.
>
>
> Sorry for being late, but the tests took a lot of time.

I know. Takes me several days to run my test scripts once.

> create table t1 as select i, md5(random()::text) from
> generate_series(0,400000000) as i;
> create index md5_idx ON  t1(md5);
> update t1 set md5 = md5((random() * (100 + 500))::text);
> vacuum;
>
> Patched vacuum used 2.9Gb of memory and vacuumed the index in one pass,
> while for old version it took three passes (1GB+1GB+0.9GB).
> Vacuum duration results:
>
> vanilla:
> LOG: duration: 4359006.327 ms  statement: vacuum verbose t1;
> patched:
> LOG: duration: 3076827.378 ms  statement: vacuum verbose t1;
>
> We can see 30% vacuum speedup. I should note that this case can be
> considered
> as favorable to vanilla vacuum: the table is not that big, it has just one
> index
> and disk used is a fast fusionIO. We can expect even more gain on slower
> disks.
>
> Thank you again for the patch. Hope to see it in 10.0.

Cool. Thanks for the review and the tests.