From: | Steve Atkins <steve(at)blighty(dot)com> |
---|---|
To: | PostgreSQL General <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: index vs. seq scan choice? |
Date: | 2007-05-25 04:25:23 |
Message-ID: | 23385219-5252-468A-BBC9-69516DA81C2A@blighty.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general pgsql-www |
On May 24, 2007, at 8:26 PM, Tom Lane wrote:
> "Joshua D. Drake" <jd(at)commandprompt(dot)com> writes:
>> Tom Lane wrote:
>>> I'm not sure I want to vote for another 10x increase by
>>> default, though.
>
>> Outside of longer analyze times, and slightly more space taken up
>> by the
>> statistics, what is the downside?
>
> Longer plan times --- several of the selfuncs.c routines grovel
> over all
> the entries in the pg_statistic row. AFAIK no one's measured the real
> impact of that, but it could easily be counterproductive for simple
> queries.
The lateness of the hour is suppressing my supposed statistics savvy,
so this may not make sense, but...
Would it be possible to look at a much larger number of samples
during analyze,
then look at the variation in those to generate a reasonable number of
pg_statistic "samples" to represent our estimate of the actual
distribution?
More datapoints for tables where the planner might benefit from it,
fewer
where it wouldn't.
Cheers,
Steve
From | Date | Subject | |
---|---|---|---|
Next Message | Michael Harris (BR/EPA) | 2007-05-25 05:45:45 | ERROR: cache lookup failed for type 0 |
Previous Message | Tom Lane | 2007-05-25 03:26:08 | Re: index vs. seq scan choice? |
From | Date | Subject | |
---|---|---|---|
Next Message | PFC | 2007-05-25 08:09:17 | Re: index vs. seq scan choice? |
Previous Message | Tom Lane | 2007-05-25 03:26:08 | Re: index vs. seq scan choice? |