Re: Precedence of standard comparison operators

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Kevin Grittner <kgrittn(at)ymail(dot)com> writes:
>> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> the precedence of <= >= and <> is neither sane nor standards compliant.

>> I wonder whether it would be feasible to have an option to generate
>> warnings (or maybe just LOG level messages?) for queries where the
>> results could differ.
>
> My guess (admittedly not yet based on much) is that warnings won't be too
> necessary. If a construction is parsed differently than before, you'll
> get no-such-operator gripes.

I have a memory of running into this in real-world production code
and that it involved booleans. I'll see whether I posted something
to the community lists about it, but it didn't take long to produce
an (admittedly artificial) case where incorrect results are
silently returned:

test=# select 'f'::boolean = 'f'::boolean >= 'f'::boolean;
?column?
----------
f
(1 row)

test=# select 'f'::boolean >= 'f'::boolean >= 'f'::boolean;
?column?
----------
t
(1 row)

--
Kevin Grittner
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