| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Artus de benque <artusdebenque(at)gmail(dot)com>, Postgres-Bugs <pgsql-bugs(at)postgresql(dot)org>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Postgresql bug report - unexpected behavior of suppress_redundant_updates_trigger |
| Date: | 2017-06-19 16:05:31 |
| Message-ID: | CA+Tgmoa5zdR38LgfB=4Tk9J8wdF0GWbMHY+KCQAL8h6MfsGMhw@mail.gmail.com |
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| Lists: | pgsql-bugs pgsql-hackers |
On Mon, Jun 19, 2017 at 11:59 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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