Re: maximum for auto_explain.log_min_duration doesn't seem to make sense

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>
Cc: Kevin Bloch <kev(at)codingthat(dot)com>, pgsql-bugs(at)lists(dot)postgresql(dot)org
Subject: Re: maximum for auto_explain.log_min_duration doesn't seem to make sense
Date: 2018-02-23 19:25:59
Message-ID: 16575.1519413959@sss.pgh.pa.us
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"David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> On Fri, Feb 23, 2018 at 11:34 AM, Kevin Bloch <kev(at)codingthat(dot)com> wrote:
>> According to https://dba.stackexchange.com/a/198429/28774 , this setting
>> maxes out at INT_MAX / 1000, but since it's never multiplied by 1000 or any
>> other number, it seems it should perhaps just be INT_MAX

> ​I suspect that the counter to which that value is being compared also
> wants to be an INT and if one checks for "val > INT_MAX" then val cannot be
> restricted to an integer (and since we are capturing time we need some
> unknown buffer).

No, a look at the code shows that it's being compared to a double.
So there's no practical problem with increasing that GUC's limit to
INT_MAX. As to whether it's worth doing, the existing limit is equivalent
to ~35 minutes if I did the math right. I can barely imagine that anyone
would want to set auto_explain.log_min_duration higher than that, but
maybe in some huge data warehouse environment it'd make sense. Anyway,
I notice that the core backend's log_min_duration GUC, which is also
measured in ms, is allowed to go up to INT_MAX; so it seems a bit
inconsistent that this one isn't.

In short, seems like a valid complaint to me.

regards, tom lane

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