Re: UPSERT wiki page, and SQL MERGE syntax

Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> On Fri, Oct 10, 2014 at 11:05 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

>> I actually like this syntax reasonably well in some ways, but I don't
>> like that we're mentioning the index name, and the CONFLICTING()
>> notation is decidedly odd.
>
> People keep remarking that they don't like that you can (optionally)
> name a unique index explicitly, and I keep telling them why I've done
> it that way [1]. There is a trade-off here. I am willing to go another
> way in that trade-off, but let's have a realistic conversation about
> it.

We've all read that, and your repeated arguments for that point of
view. We disagree and have said why. What in that is not a
realistic conversation?

To restate: to do so is conflating the logical definition of the
database with a particular implementation detail. As just one
reason that is a bad idea: we can look up unique indexes on the
specified columns, but if we implement a other storage techniques
where there is no such thing as a unique index on the columns, yet
manage to duplicate the semantics (yes, stranger things have
happened), people can't migrate to the new structure without
rewriting their queries. If the syntax references logical details
(like column names) there is no need to rewrite. We don't want to
be painted into a corner.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company