Re: Command Triggers patch v18

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> I am coming more and more strongly to the conclusion that we're going
> in the wrong direction here. It seems to me that you're spending an
> enormous amount of energy implementing something that goes by the name
> COMMAND TRIGGER when what you really want is an EVENT TRIGGER.

No.

The following two features are not allowed by what you call an EVENT
TRIGGER yet the very reason why I started working on COMMAND TRIGGERs:

- BEFORE COMMAND TRIGGER
- Having the command string available in the command trigger

Now, because of scheduling, the current patch has been reduced not to
include the second feature yet, which is a good trade-off for now. Yet
it's entirely possible to implement such feature as an extension once
9.2 is out given current COMMAND TRIGGER patch.

> I realize this represents a radical design change from what you have
> right now, but what you have right now is messy and ill-defined and I

That's only because I've not been doing the hard choices alone, I wanted
to be able to speak about them here, and the only time that discussion
happen is when serious hand down code review is being done.

My take? Let's make the hard decisions together. Mechanisms are
implemented. The plural is what is causing problems here, but that also
mean we can indeed implement several policies now.

I've been proposing a non-messy policy in a previous mail, which I
realize the patch is not properly implementing now. I'd think moving the
patch to implement said policy (or another one after discussion) is next
step.

> don't think you can easily fix it. You're exposing great gobs of
> implementation details which means that, inevitably, every time anyone
> wants to refactor some code, the semantics of command triggers are
> going to change, or else the developer will have to go to great
> lengths to ensure that they don't. I don't think either of those
> things is going to make anyone very happy.

I guess you can't really have your cake and eat it too, right?

Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support