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

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