Re: Cascade Trigger Not Firing

On 9/13/19 8:07 PM, Judy Loomis wrote:
> At the very least that note about this behavior should be highlighted, 
> probably on the Trigger Behavior page and not buried in a bunch of notes 
> on the Create Trigger page.

I know this after the fact. Still, as a general rule the best place to 
start when learning about a command is on it's respective page under here:

https://www.postgresql.org/docs/11/sql-commands.html

Further I usually go to the Notes after reading the synopsis, as Notes 
is where the exceptions to the rules and gotchas are called out.

> 
> 
> 
> On Fri, Sep 13, 2019 at 4:03 PM Tom Lane <tgl@sss.pgh.pa.us 
> <mailto:tgl@sss.pgh.pa.us>> wrote:
> 
>     Judy Loomis <hoodie.judy@gmail.com <mailto:hoodie.judy@gmail.com>>
>     writes:
>      > I'm going to have to really look at all my BEFORE UPDATE triggers
>     and make
>      > sure we're not missing any more.
>      > And I have to stop telling management that a trigger means we
>     always know
>      > when a value changes.
> 
>     Well, you can rely on that, just not like this.  Use an AFTER trigger
>     (else, you can't be sure it fires after all the BEFORE triggers)
>     and instead of triggering it with a column parameter, have it do
>     something like "if old.col is distinct from new.col".
> 
>     Yeah, it's a bit slower that way, but there's no free lunch,
>     especially if you don't trust your other triggers.  (Although,
>     if you have so many triggers that that's a problem, I think you
>     might have some other design issues.)
> 
>                              regards, tom lane
> 
> 
> 
> -- 
> 
> ----------------------------------------------------------
> *Judy Loomis*
> 469.235.5839


-- 
Adrian Klaver
adrian.klaver@aklaver.com