Re: Should TIDs be typbyval = FLOAT8PASSBYVAL to speed up CREATE INDEX CONCURRENTLY?

On Wed, Dec 16, 2015 at 4:24 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:

> On Wed, Dec 16, 2015 at 12:28 PM, Robert Haas <robertmhaas(at)gmail(dot)com>
> wrote:
> >> I seem to be able to produce these sorting patches at a much greater
> >> rate than they can be committed, in part because Robert is the only
> >> one that ever reviews them, and he is only one person.
> >
> > I object to that vicious slander. I am at least three people, if not
> more!
>
> I was referring only to the Robert that reviews my sorting patches. :-)
>
> > Meanwhile, I did some simple benchmarking on your latest patch on my
> > MacBook Pro. I did pgbench -i -s 100 and then tried:
> >
> > create index x on pgbench_accounts (aid);
> > create index concurrently x on pgbench_accounts (aid);
> >
> > The first took about 6.9 seconds. The second took about 11.3 seconds
> > patched versus 14.6 seconds unpatched. That's certainly a healthy
> > improvement.
>
> That seems pretty good. It probably doesn't matter, but FWIW it's
> likely that your numbers are not as good as mine because this ends up
> with a perfect logical/physical correlation, which the quicksort
> precheck [1] does very well on when sorting the TIDs (since input is
> *perfectly* correlated, as opposed to 99.99% correlated, a case that
> does poorly [2]).
>
> > I have also reviewed the code, and it looks OK to me, so committed.
>
> Thanks!
>
> [1] Commit a3f0b3d68f9a5357a3f72b40a45bcc714a9e0649
> [2] http://www.postgresql.org/message-id/54EB580C.2000904@2ndquadrant.com
> --
> Peter Geoghegan
>
>
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My apologies to Peter and all the Roberts, I wasn't able to set up a test
fast enough. Glad it got committed.