Re: Detecting changes to certain fields in 'before update' trigger functions

On Mon, Dec 1, 2008 at 8:35 AM, Sebastian Tennant
<sebyte(at)smolny(dot)plus(dot)com> wrote:
>>> IF (NEW.<column-name> != OLD.<column-name>) THEN ...
>>
>> IF( NEW.* IS DISTINCT FROM OLD.* ) THEN ...
>
> I sometimes think this kind of gotcha is purposely buried, or not
> addressed at all, in order to force users to read the manual.

I wouldn't say it is intentionally buried. I would say that the
PostgreSQL manual focuses primarily is on "What are the PG features".
While the manual may at times document some of the good/best
practices to use by combining various PG features, I wouldn't say
that its intention isn't to be an authoritative source on "How to use
PG features."

On the other hand, there are many ANSI-SQL books that focus on good
practices. For example, the need for the "IS DISTINCT FROM" when
dealing with nulls would be discussed in an SQL book. Once you have
the theory down, you can turn to the PostgreSQL manual to find out how
PostgreSQL implements this functionality.

--
Regards,
Richard Broersma Jr.

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