Question: what is proper way to define python function as event_trigger?

[Andrei Pozolotin]

Hello. 

Problem: 

1. any attempt to define python function as an event_trigger, i.e.: 

CREATE FUNCTION public.verify()
RETURNS event_trigger
LANGUAGE 'plpython3u'
AS $$ print("hello-kitty") $$; 

2. fails with message: 

ERROR: trigger functions can only be called as triggers 

SQL state: 0A000 

3. here in the source: 

https://github.com/postgres/postgres/blob/master/src/pl/plpython/plpy_procedure.c#L226


Question: 

what is proper way to define python function as event_trigger? 

Thank you.

Re: Question: what is proper way to define python function as event_trigger?

[Andrei Pozolotin]

Jeff, hi:

1. my concern is global "event_trigger" for DDL, not per-table "trigger" 
for DML


2. regardless - thank you for the link, I found it helpful

3. Tom Lane says event_trigger is just not implemented in plpython

Andrei.

On 2019-12-22 17:20, Jeff Ross wrote:

On 2019-12-22 16:07, Jeff Ross wrote:

On 2019-12-22 15:27, Andrei Pozolotin wrote:


Hello.

Problem:

1. any attempt to define python function as an event_trigger, i.e.:

CREATE FUNCTION public.verify()
RETURNS event_trigger
LANGUAGE 'plpython3u'
AS $$ print("hello-kitty") $$;

2. fails with message:

ERROR: trigger functions can only be called as triggers

SQL state: 0A000

3. here in the source:

https://github.com/postgres/postgres/blob/master/src/pl/plpython/plpy_procedure.c#L226 
Question:


what is proper way to define python function as event_trigger?

Thank you.



Just do

"create function public.verify() as trigger..."

My bad--that should be "create function public.verify() returns 
trigger... "


Jeff

Re: Question: what is proper way to define python function as event_trigger?

[Andrei Pozolotin]

Tom, hi:

1. actual use case has to do with:
BUG #16177: pg_event_trigger_ddl_commands() returns empty set for 
ddl_command_start and "drop table"

https://www.postgresql.org/message-id/16177-053a34714817c3e1%40postgresql.org

2. I was merely hoping to re-implement pg_event_trigger_ddl_commands as 
part of python event_trigger


3. do you think "pg_event_trigger_ddl_commands" is any easier to fix 
then "support event_trigger in python"?


Thank you,

Andrei

On 2019-12-22 17:40, Tom Lane wrote:

Andrei Pozolotin  writes:

1. any attempt to define python function as an event_trigger, i.e.:


AFAICS, there's not really any event trigger support in plpython.
That feature has only been built out in the other three PLs.

Somebody oughta fix this sometime, I guess, but it evidently hasn't
been high priority.  If you feel like working on it, you could look
at commits e5dc4cc24d2e1e94ac572a2c64103710bf15d21e (for plperl)
and/or a5036ca998a6058f60913d43a80badfcbb65f5bb (for pltcl).

regards, tom lane