Re: GIN improvements part 1: additional information

On Sat, Jan 11, 2014 at 6:15 AM, Tomas Vondra <tv(at)fuzzy(dot)cz> wrote:

> On 8.1.2014 22:58, Alexander Korotkov wrote:
> > Thanks for reporting. Fixed version is attached.
>
> I've tried to rerun the 'archie' benchmark with the current patch, and
> once again I got
>
> PANIC: could not split GIN page, didn't fit
>
> I reran it with '--enable-cassert' and with that I got
>
> TRAP: FailedAssertion("!(ginCompareItemPointers(&items[i - 1],
> &items[i]) < 0)", File: "gindatapage.c", Line: 149)
> LOG: server process (PID 5364) was terminated by signal 6: Aborted
> DETAIL: Failed process was running: INSERT INTO messages ...
>
> so the assert in GinDataLeafPageGetUncompressed fails for some reason.
>
> I can easily reproduce it, but my knowledge in this area is rather
> limited so I'm not entirely sure what to look for.

I've fixed this bug and many other bug. Now patch passes test suite that
I've used earlier. The results are so:

Operations time:
event | period
-----------------------+-----------------
index_build | 00:01:47.53915
index_build_recovery | 00:00:04
index_update | 00:05:24.388163
index_update_recovery | 00:00:53
search_new | 00:24:02.289384
search_updated | 00:27:09.193343
(6 rows)

Index sizes:
label | size
---------------+-----------
new | 384761856
after_updates | 667942912
(2 rows)

Also, I made following changes in algorithms:

- Now, there is a limit to number of uncompressed TIDs in the page.
After reaching this limit, they are encoded independent on if they can fit
page. That seems to me more desirable behaviour and somehow it accelerates
search speed. Before this change times were following:

event | period
-----------------------+-----------------
index_build | 00:01:51.467888
index_build_recovery | 00:00:04
index_update | 00:05:03.315155
index_update_recovery | 00:00:51
search_new | 00:24:43.194882
search_updated | 00:28:36.316784
(6 rows)

- Page are not fully re-encoded if it's enough to re-encode just last
segment.

README is updated.

------
With best regards,
Alexander Korotkov.