Re: [HACKERS] Postgresql bug report - unexpected behavior of suppress_redundant_updates_trigger

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Mon, Jun 19, 2017 at 11:59 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I don't think it's a bug, I think it's an intentional design tradeoff.
>> To suppress an update in this case, the trigger would have to grovel
>> through the individual fields and detoast them before comparing.
>> That would add a lot of cycles, and only seldom add successes.
>>
>> Possibly we should adjust the documentation so that it doesn't imply
>> that this trigger guarantees to suppress every no-op update.

> That doesn't sound like a very plausible argument to me. I don't
> think that a proposal to add a function named
> sometimes_suppress_redundant_updates_trigger() would've attracted many
> votes.

You'd be wrong. The entire point of this trigger is to save cycles,
so having it eat a lot of cycles only to fail is not an improvement.

regards, tom lane