Re: INSERT ... ON CONFLICT {UPDATE | IGNORE} 2.0

On Tue, Feb 10, 2015 at 12:09 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
>> Then the problem suddenly becomes that previous choices of
>> indexes/statements aren't possible anymore. It seems much better to
>> introduce the syntax now and not have too much of a usecase for
>> it.
>
> The only way the lack of a way of specifying which opclass to use
> could bite us is if there were two *actually* defined unique indexes
> on the same column, each with different "equality" operators. That
> seems like kind of a funny scenario, even if that were quite possible
> (even if non-default opclasses existed that had a non-identical
> "equality" operators, which is basically not the case today).
>
> I grant that is a bit odd that we're talking about unique indexes
> definitions affecting semantics, but that is to a certain extent the
> nature of the beast. As a compromise, I suggest having the inference
> specification optionally accept a named opclass per attribute, in the
> style of CREATE INDEX (I'm already reusing a bit of the raw parser
> support for CREATE INDEX, you see) - that'll make inference insist on
> that opclass, rather than make it a strict matter of costing available
> alternatives (not that any alternative is expected with idiomatic
> usage). That implies no additional parser overhead, really. If that's
> considered ugly, then at least it's an ugly thing that literally no
> one will ever use in the foreseeable future...and an ugly thing that
> is no more necessary in CREATE INDEX than here (and yet CREATE INDEX
> lives with the ugliness).

Any thoughts on this, anyone?

AFAICT, only this and the behavior of logical decoding are open items
at this point. I'd like to close out both of those sooner rather than
later.

Thanks
--
Peter Geoghegan