From: | David Fetter <david(at)fetter(dot)org> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Pantelis Theodosiou <ypercube(at)gmail(dot)com>, Joel Jacobson <joel(at)trustly(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Idea on how to simplify comparing two sets |
Date: | 2017-02-08 17:15:02 |
Message-ID: | 20170208171502.GA10277@fetter.org |
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Thread: | |
Lists: | pgsql-hackers |
On Wed, Feb 08, 2017 at 11:22:56AM -0500, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > On Wed, Feb 8, 2017 at 4:24 AM, Pantelis Theodosiou <ypercube(at)gmail(dot)com> wrote:
> >> I'm not advocating it but I don't see how introducing new SQL keywords
> >> breaks backwards compatibility.
>
> > It does at least a little bit.
>
> Yes. I think a new set-operation keyword would inevitably have to
> be fully reserved --- UNION, INTERSECT, and EXCEPT all are --- which
> means that you'd break every application that has used that word as
> a table, column, or function name.
I've long wanted a SYMMETRIC DIFFERENCE join type, that being the only
elementary set operation not included in join types, but nobody at the
SQL standards committee seems to have cared enough to help.
> Generally speaking, we try very darn hard not to introduce new
> reserved words that are not called out as reserved in the SQL
> standard. (And even for those, we've sometimes made the grammar
> jump through hoops so as not to reserve a word that we didn't
> reserve previously.)
We just never know what new keywords the standards committee will
dream up, or what silliness they'll introduce in the grammar :/
Best,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
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