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

On Mon, Jun 19, 2017 at 11:59 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Seems like in "suppress_redundant_updates_trigger"  we are comparing
>> toasted tuple with the new tuple and that is the cause of the bug.
>
> 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.

-- 
Robert Haas
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