Re: Actual Cost - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Actual Cost
Date
Msg-id 9871.1550381493@sss.pgh.pa.us
Whole thread Raw
In response to Re: Actual Cost  (Donald Dong <xdong@csumb.edu>)
Responses Re: Actual Cost  (Donald Dong <xdong@csumb.edu>)
List pgsql-hackers
Donald Dong <xdong@csumb.edu> writes:
> On Feb 16, 2019, at 6:44 PM, Tomas Vondra wrote:
>> I don't quite understand what is meant by "actual cost metric" and/or
>> how is that different from running EXPLAIN ANALYZE.

> Here is an example:

> Hash Join  (cost=3.92..18545.70 rows=34 width=32) (actual cost=3.92..18500 time=209.820..1168.831 rows=47 loops=3)

> Now we have the actual time. Time can have a high variance (a change
> in system load, or just noises), but I think the actual cost would be
> less likely to change due to external factors.

I'm with Tomas: you have not explained what you think those
numbers mean.

            regards, tom lane


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