Re: Collect frequency statistics for arrays
| От | Alexander Korotkov |
|---|---|
| Тема | Re: Collect frequency statistics for arrays |
| Дата | |
| Msg-id | CAPpHfdsqAaWN4fqzLXK-fmY3VeXti1=i0Q-DEsyP2VrOcnSzuw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Collect frequency statistics for arrays (Noah Misch <noah@leadboat.com>) |
| Ответы |
Re: Collect frequency statistics for arrays
|
| Список | pgsql-hackers |
On Mon, Jan 23, 2012 at 7:58 PM, Noah Misch <noah@leadboat.com> wrote:
------> + /* Take care about events with low probabilities. */> + if (rest > DEFAULT_CONTAIN_SEL)
> + {
Why the change from "rest > 0" to this in the latest version?
Ealier addition of "rest" distribution require O(m) time. Now there is a more accurate and proved estimate, but it takes O(m^2) time.It doesn't make general assymptotical time worse, but it significant. That's why I decided to skip for low values of "rest" which don't change distribution significantly.
> + /* emit some statistics for debug purposes */
> + elog(DEBUG3, "array: target # mces = %d, bucket width = %d, "
> + "# elements = %llu, hashtable size = %d, usable entries = %d",
> + num_mcelem, bucket_width, element_no, i, track_len);
That should be UINT64_FMT. (I introduced that error in v0.10.)
I've attached a new version that includes the UINT64_FMT fix, some edits of
your newest comments, and a rerun of pgindent on the new files. I see no
other issues precluding commit, so I am marking the patch Ready for Committer.
Great!
If I made any of the comments worse, please post another update.
Changes looks reasonable for me. Thanks!
With best regards,
Alexander Korotkov.
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