在 postgres 中触发以使用列表锁定表

Question

I have an issue regarding a Triggers with PostgreSQL 10. Here is the situation.
I have a table called index_name which contain à column named index_ref. Into this field I have created a list of value as example: PBM PI, PBM PO, etc.
I would like to use this table to store valid name as reference for another table called gis_osm_places. So, whenever someone try to insert a value not into the list then an exception message will pop-up to say:
NOT ALLOWED COMMIT. PLEASE USE: (reference list)

Here are my tables:


Here is where I am with the trigger:

CREATE FUNCTION public.check_column_value()
    RETURNS trigger
    LANGUAGE 'plpgsql'
    COST 100
    VOLATILE NOT LEAKPROOF

AS $BODY$

DECLARE
ref_allowed character varying;
BEGIN

IF TG_OP = 'INSERT' OR TG_OP = 'UPDATE'
THEN

IF NEW.index_a is not null OR NEW.index_a NOT IN (SELECT index_ref from public.index_name)
THEN

ref_allowed := (SELECT string_agg(index_ref,',') from public.index_name);
RAISE EXCEPTION 'NOT ALLOWED COMMIT. PLEASE USE : %',ref_allowed;

END IF;
RETURN NEW;

END IF;
END;

$BODY$;

ALTER FUNCTION public.check_column_value()
    OWNER TO "postgres";

CREATE TRIGGER check_column_value
    BEFORE INSERT
    ON public.gis_osm_places
    FOR EACH ROW
    EXECUTE PROCEDURE public.check_column_value();

Actually nothing is happening, I mean I can add whatever I want without an error.
Any idea or upgrade of the code would be greatly appreciate.
Thanks in advance !

Answer 1

You do not need not and do not want a trigger for this. This functionality is build in. Just create a Foreign Key constraint on gis_osm_places referencing index_name.

alter table gis_osm_places 
  add constraint osm_places2index_fk 
      foreign key (index_a)
      references index_name(index_ref);

Now drop your trigger and the trigger function. The downside being you do not get the message you have created. But you handle that in your exception processing in the your app.

Answer 2

I finally found what went wrong !

CREATE FUNCTION public.check_column_value()
    RETURNS trigger
    LANGUAGE 'plpgsql'
    COST 100
    VOLATILE NOT LEAKPROOF

AS $BODY$

DECLARE
ref_allowed character varying;
BEGIN

IF TG_OP = 'INSERT' OR TG_OP = 'UPDATE'
THEN

IF NEW.index_a is not null AND NEW.index_a NOT IN (SELECT index_ref from public.index_name)
THEN

ref_allowed := (SELECT string_agg(index_ref,',') from public.index_name);
RAISE EXCEPTION 'NOT ALLOWED COMMIT. PLEASE USE : %',ref_allowed;

END IF;
RETURN NEW;

END IF;
END;

$BODY$;

ALTER FUNCTION public.check_column_value()
    OWNER TO "postgres";

CREATE TRIGGER check_column_value
    BEFORE INSERT OR UPDATE
    ON public.gis_osm_places
    FOR EACH ROW
    EXECUTE PROCEDURE public.check_column_value();