| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
| Cc: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Proposal: revert behavior of IS NULL on row types |
| Date: | 2016-07-26 19:35:43 |
| Message-ID: | 7825.1469561743@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
"David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> The concept embodied by "NULL" in the operator "IS [NOT] NULL" is distinct
> from the concept embodied by "NULL" in the operator "IS [NOT] DISTINCT
> FROM".
> In short, the former smooths out the differences between composite and
> non-composite types while the later maintains their differences. While a
> bit confusing I don't see that there is much to be done about it - aside
> from making the distinction more clear at:
> https://www.postgresql.org/docs/devel/static/functions-comparison.html
> Does spec support or refute this distinction in treatment?
AFAICS, the IS [NOT] DISTINCT FROM operator indeed is specified to do the
"obvious" thing when one operand is NULL: you get a simple nullness check
on the other operand. So I went ahead and documented that it could be
used for that purpose.
regards, tom lane
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