From: | Noah Misch <noah(at)leadboat(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Precedence of standard comparison operators |
Date: | 2015-08-09 23:36:31 |
Message-ID: | 20150809233631.GC1900437@tornado.leadboat.com |
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Lists: | pgsql-hackers |
On Sun, Aug 09, 2015 at 07:16:02PM -0400, Tom Lane wrote:
> Noah Misch <noah(at)leadboat(dot)com> writes:
> > On Sun, Aug 09, 2015 at 06:44:58PM -0400, Tom Lane wrote:
> >> So for our
> >> purposes, it's better to keep BETWEEN and friends as binding slightly
> >> tighter than '<' than to make them the same precedence. Same precedence
> >> risks breaking things that weren't broken before.
>
> > It does risk that. Same deal with making "=" have the same precedence as "<"
> > instead of keeping it slightly lower.
>
> Agreed, but in that case I think our hand is forced by the SQL standard.
In SQL:2008 and SQL:2011 at least, "=", "<" and "BETWEEN" are all in the same
boat. They have no precedence relationships to each other; SQL sidesteps the
question by requiring parentheses. They share a set of precedence
relationships to other constructs. SQL does not imply whether to put them in
one %nonassoc precedence group or in a few, but we can contemplate whether
users prefer an error or prefer the 9.4 behavior for affected queries.
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