| From: | Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>, 'pinker *EXTERN*' <pinker(at)onet(dot)eu>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Shouldn't "WHEN (OLD.* IS DISTINCT FROM NEW.*)" clause be independent from data type? |
| Date: | 2015-09-17 14:57:37 |
| Message-ID: | 55FAD4E1.5090608@aklaver.com |
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| Lists: | pgsql-general |
On 09/17/2015 07:51 AM, Tom Lane wrote:
> Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> writes:
>> On 09/17/2015 07:34 AM, Tom Lane wrote:
>>> Ah, sorry, actually what IS [NOT] DISTINCT FROM looks up is the "="
>>> operator.
>
>> So the docs should be changed?
>> As they stand now:
>> http://www.postgresql.org/docs/9.4/interactive/functions-comparison.html
>> "For non-null inputs, IS DISTINCT FROM is the same as the <> operator."
>
> Well, it's an oversimplification to begin with. Do we want to try to
> cram all of these implementation details in there?
No, just that IS DISTINCT ON is dependent on '=' and will not work on
data types that do not have that operator. That would also cover the IS
NOT DISTINCT FROM case where '=' is the operator 'alias'.
>
> regards, tom lane
>
--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com
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