| From: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
|---|---|
| To: | David Fetter <david(at)fetter(dot)org>, Donald Dong <xdong(at)csumb(dot)edu> |
| Cc: | pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Actual Cost |
| Date: | 2019-02-17 02:44:25 |
| Message-ID: | f38567a0-bf17-e9c7-48d8-34616095c1cb@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 2/17/19 3:40 AM, David Fetter wrote:
> On Sat, Feb 16, 2019 at 03:10:44PM -0800, Donald Dong wrote:
>> Hi,
>>
>> When explaining a query, I think knowing the actual rows and pages
>> in addition to the operation type (e.g seqscan) would be enough to
>> calculate the actual cost. The actual cost metric could be useful
>> when we want to look into how off is the planner's estimation, and
>> the correlation between time and cost. Would it be a feature worth
>> considering?
>
> As someone not volunteering to do any of the work, I think it'd be a
> nice thing to have. How large an effort would you guess it would be
> to build a proof of concept?
>
I don't quite understand what is meant by "actual cost metric" and/or
how is that different from running EXPLAIN ANALYZE.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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