Re: Precedence of standard comparison operators

Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Kevin Grittner <kgrittn@ymail.com> writes:
>> Tom Lane <tgl@sss.pgh.pa.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
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company