errore PostgreSQL trigger

Question

ho:

CREATE OR REPLACE FUNCTION aktualizujIloscPodan() RETURNS TRIGGER AS 
$BODY$ 
    DECLARE 
    n integer; 
    sid integer; 
BEGIN 

sid=0; 
IF (TG_OP='INSERT') THEN 
sid = NEW."studentID"; 
ELSIF (TG_OP='DELETE') THEN 
sid = OLD."studentID"; 
END IF; 

n = COALESCE ((SELECT count("studentID") as c 
FROM "Podania" WHERE "studentID"=sid 
GROUP BY "studentID"), 0); 

UPDATE "Studenci" SET "licznikpodan" = n WHERE "ID"=sid; 
END; 
$BODY$ 
LANGUAGE plpgsql; 

DROP TRIGGER IF EXISTS triggenPodan ON "Podania"; 

CREATE TRIGGER triggenPodan AFTER INSERT OR DELETE 
ON "Podania" 
EXECUTE PROCEDURE aktualizujIloscPodan(); 

Quando provo ad eseguire:

DELETE FROM "Podania" 

I get 

ERROR: record "old" is not assigned yet 
DETAIL: The tuple structure of a not-yet-assigned record is indeterminate. 
CONTEXT: PL/pgSQL function "aktualizujiloscpodan" line 11 at assignment 

********** Błąd ********** 

ERROR: record "old" is not assigned yet 
Stan SQL:55000 
Szczegóły:The tuple structure of a not-yet-assigned record is indeterminate. 
Kontekst:PL/pgSQL function "aktualizujiloscpodan" line 11 at assignment 

Sembra che non sa che cosa è OLD o NEW. Come posso ripararlo?

Answer 1

È necessario utilizzare FOR EACH ROW

CREATE TRIGGER triggerPodan AFTER INSERT OR DELETE 
ON "Podania" FOR EACH ROW 
EXECUTE PROCEDURE aktualizujIloscPodan(); 

Answer 2

Per il trigger solo il record OLD è definito e NEW non è definito. Quindi, nel codice, controlla se il trigger funziona come DELETE o INSERT (variabile TG_OP) e accedi al record appropriato.

Inoltre, si può andare senza contare qui a tutti, in questo modo:

CREATE OR REPLACE FUNCTION aktualizujIloscPodan() RETURNS TRIGGER AS 
$BODY$ 
DECLARE 
    n integer; 
BEGIN 
    IF TG_OP = 'INSERT' then 
     UPDATE "Studenci" SET "ilosc_podan" = "ilosc_podan" + 1 WHERE "ID"=NEW."studentID"; 
    ELSIF TG_OP = 'DELETE' then 
     UPDATE "Studenci" SET "ilosc_podan" = "ilosc_podan" - 1 WHERE "ID"=OLD."studentID"; 

    END IF; 
END; 

$BODY$ 
LANGUAGE plpgsql; 

DROP TRIGGER IF EXISTS triggenPodan ON "Podania"; 

CREATE TRIGGER triggenPodan AFTER INSERT OR DELETE 
ON "Podania" 
EXECUTE PROCEDURE aktualizujIloscPodan();