Re: Hide 'Execution time' in EXPLAIN (COSTS OFF)

From: Andres Freund <andres(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, ronan(at)dunklau(dot)fr, Christoph Berg <cb(at)df7cb(dot)de>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Markus Wanner <markus(at)bluegap(dot)ch>
Subject: Re: Hide 'Execution time' in EXPLAIN (COSTS OFF)
Date: 2014-10-16 14:12:21
Message-ID: 20141016141221.GA19064@alap3.anarazel.de
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On 2014-10-16 10:06:59 -0400, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > On Tue, Oct 14, 2014 at 3:03 AM, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> >> Hmm, was my case above not compelling enough?
>
> > Apparently not to Tom, but it made sense to me.
>
> No, it wasn't. I'm not convinced either that that patch will get in at
> all, or that it has to have regression tests of that particular form,
> or that such a switch would be sufficient to make such tests platform
> independent.

It's not like we don't already have features where that capability
actually would be useful. E.g. testing that certain nodes aren't reached
during execution and instead '(never executed)' and things like that.

Why should the EXPLAIN ANALYZE output without timing information be less
consistent for sensibly selected cases than EXPLAIN itself? I'd actually
say stats are harder to get right than the actual number of rows.

There also have been bugs where this capability would have been
useful. And don't say that regression testing wouldn't have helped there
- the case I'm thinking of was broken several times over the years.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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