From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
cc: Andres Freund <andres@anarazel.de>, Andrew Dunstan <andrew@dunslane.net>,
        Robert Haas <robertmhaas@gmail.com>,
        pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Cleaning up historical portability baggage
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Comments: In-reply-to Thomas Munro <thomas.munro@gmail.com>
	message dated "Thu, 04 Aug 2022 16:18:40 +1200"
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Date: Sun, 07 Aug 2022 20:27:27 -0400
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Thomas Munro <thomas.munro@gmail.com> writes:
> On Thu, Aug 4, 2022 at 4:09 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> clock_gettime is required by SUSv2 (1997), so I have to admit that
>> macOS 10.4 doesn't have a lot of excuse not to have it.  In any case,
>> prairiedog is just sitting there doing its thing until I find cycles
>> to install a newer OS.  If you want to move ahead with this, don't
>> let prairiedog block you.

> Thanks, will do.

BTW, that commit really should have updated the explanation at the top of
instr_time.h:

 * This file provides an abstraction layer to hide portability issues in
 * interval timing.  On Unix we use clock_gettime() if available, else
 * gettimeofday().  On Windows, gettimeofday() gives a low-precision result
 * so we must use QueryPerformanceCounter() instead.  These macros also give
 * some breathing room to use other high-precision-timing APIs.

Updating the second sentence is easy enough, but as for the third,
I wonder if it's still true in view of 24c3ce8f1.  Should we revisit
whether to use gettimeofday vs. QueryPerformanceCounter?  At the very
least I suspect it's no longer about "low precision", but about which
API is faster.

			regards, tom lane