Re: event trigger support for PL/Python

čt 7. 8. 2025 v 2:35 odesílatel Euler Taveira <euler(at)eulerto(dot)com> napsal:

> On Wed, Aug 6, 2025, at 5:16 PM, Pavel Stehule wrote:
> >
> > I am checking the code, and I don't like too much an introduction of
> > PLPyTrigType - more when it is used in
> > the pair with variable is_trigger. This combination looks strange and
> > it is a little bit difficult to read for me.
> >
> > Maybe I prefer some like
> >
> > typedef enum {
> > PLPY_CALLED_AS_TRIGGER,
> > PLPY_CALLED_AS_EVENT_TRIGGER,
> > PLPY_CALLED_AS_FUNCTION
> > } PLPyCallType;
> >
>
> I used the same pattern as PL/pgSQL
>

I see it

>
> typedef enum PLpgSQL_trigtype
> {
> PLPGSQL_DML_TRIGGER,
> PLPGSQL_EVENT_TRIGGER,
> PLPGSQL_NOT_TRIGGER,
> } PLpgSQL_trigtype;
>
> Are you suggesting that we should modify it too?
>

I am not happy about it, but maybe not, and it is a different issue. I
think fn_is_trigger is a little bit of a messy name too. It worked when
there was no other type of trigger and this variable was boolean. But the
rename breaks plpgsql plugins :-/, and I am not sure if it is an acceptable
cost. Although there are probably four plpgsql plugins, and the change can
be minimal and easy (and well detected)

Minimally - you should to use PLPY_DML_TRIGGER instead PLPY_TRIGGER

>
> > and then instead
> >
> > if (is_trigger == PLPY_NOT_TRIGGER)
> >
> > the code can looks like
> >
> > if (call_type == PLPY_CALLED_AS_FUNCTION)
> > {
> >
> > }
> >
>
> The is_trigger variable is similar to fn_is_trigger in PL/pgSQL (see
> PLpgSQL_function). If this variable is not clear maybe a prefix should
> avoid
> confusion.
>
>
Maybe the name "trigtype" can be better than "is_trigger". The similarity
with PLpgSQL has some benefits, but in this case I think so the plpgsql
design (of this case) is minimally confusing (and really the related part
in plpgsql_compile_callback can be cleaned). How much - this is a question.
There are two different things that are mixed together (and this is what I
dislike):

a) how the function was defined - RETURNS trigger, RETURNS event_trigger,
or something else

b) how the function was called - as dml trigger, as event trigger, or as
function or procedure

You can see, the event trigger has minimal intersection with the dml
trigger - but using the name "is_trigger" or "fn_is_trigger" implies
stronger relations between dml triggers and event triggers.

What do you think?

Regards

Pavel

>
> --
> Euler Taveira
> EDB https://www.enterprisedb.com/
>