Re: [HACKERS] pg_stat_activity.waiting_start

On Thu, Jan  5, 2017 at 06:48:17PM -1000, Joel Jacobson wrote:
> On Thu, Jan 5, 2017 at 4:59 PM, Bruce Momjian <bruce@momjian.us> wrote:
> > Agreed.  No need in adding overhead for short-lived locks because the
> > milli-second values are going to be meaningless to users. I would be
> > happy if we could find some weasel value for non-heavyweight locks.
> 
> To avoid a NULL value for waiting_start, and thanks to non-heavyweight
> locks don't exceed order-of-milliseconds, I think it would be
> acceptable to just return now() whenever something wants to know
> waiting_start i.e. when something selects from pg_stat_activity.
> 
> The exact value would only be within orders-of-milliseconds away from
> now() anyway, so one can argue it's not that important, as long as the
> documentation is clear on that point.

I don't think now() is a good value as it doesn't indicate to the user
which values are real measurements and which are not.  NULL is probably
the best.  +/-infinity is odd too.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
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