Date: Thu, 26 Jan 2023 12:23:01 -0800
From: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Thomas Munro <thomas.munro@gmail.com>,
	"Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: suppressing useless wakeups in logical/worker.c
Message-ID: <20230126202301.GA1703463@nathanxps13>
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On Thu, Jan 26, 2023 at 03:04:30PM -0500, Tom Lane wrote:
> Nathan Bossart <nathandbossart@gmail.com> writes:
>> I wonder if we should explicitly reject negative timestamps to eliminate
>> any chance of int64 overflow, too.
> 
> Hmm.  I'm disinclined to add an assumption that the epoch is in the past,
> but I take your point that the subtraction would overflow with
> TIMESTAMP_INFINITY and a negative finite timestamp.  Maybe we should
> make use of pg_sub_s64_overflow()?

That would be my vote.  I think the 'diff <= 0' check might need to be
replaced with something like 'start_time > stop_time' so that we return 0
for the underflow case.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com