| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, jd(at)commandprompt(dot)com, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Better estimates of index correlation |
| Date: | 2011-03-15 00:53:56 |
| Message-ID: | 4D7EB8A4.2040503@agliodbs.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On 3/14/11 5:51 PM, Tom Lane wrote:
> Josh Berkus <josh(at)agliodbs(dot)com> writes:
>>> I'm not convinced you can get a sufficiently good estimate from a small
>>> subset of pages.
>
>> Note that if this requires VACUUM rather than ANALYZE, it introduces a
>> problem for data warehousing users, who can go years between vacuums of
>> their largest tables.
>
> It's likely that the default estimate of zero index correlation will
> work just fine for such users ...
No, it isn't. In fact, users with very large tables are the ones
hardest hit by our lack of correlation stats.
--
-- Josh Berkus
PostgreSQL Experts Inc.
http://www.pgexperts.com
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Robert Haas | 2011-03-15 01:07:43 | Re: dependency between numbers keywords and parser speed |
| Previous Message | Tom Lane | 2011-03-15 00:51:44 | Re: Better estimates of index correlation |