Re: Triggers on columns - Mailing list pgsql-hackers

From Peter Eisentraut
Subject Re: Triggers on columns
Date
Msg-id 1252310037.29289.12.camel@fsopti579.F-Secure.com
Whole thread Raw
In response to Re: Triggers on columns  (Itagaki Takahiro <itagaki.takahiro@oss.ntt.co.jp>)
Responses Re: Triggers on columns
List pgsql-hackers
On Mon, 2009-09-07 at 11:20 +0900, Itagaki Takahiro wrote:
> We are discussing how to determine modified columns
> (UPDATE-target vs. changes of actual values), but in the patch
> I used value-based checking. The reasons are:

If you implement a new feature using syntax from the standard, you have
to implement the semantics of the standard.  If you don't like the
semantics of the standard, use a different syntax.

>     2. IMHO, almost users don't expect their triggers are not called
>        if the actual values are not modified.

Well, as we saw upthread, there can be different valid opinions on this.
But consider the following:

- Statement triggers are called even if the table was not actually
changed in a semantically significant way.

- Row triggers are called even if the row was not actually changed in a
semantically significant way.

Therefore, it cannot be completely unexpected if column triggers are
called even if the column was not actually changed in a semantically
significant way.




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