PostgreSQL触发器错误

Question

我有：

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();

当我尝试执行以下命令时：

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

看起来它不知道什么是OLD或NEW。 我该如何修复？

- Miko Kronn

Answer 1

你需要使用 FOR EACH ROW

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

- Ichibann

Answer 2

对于delete触发器，只定义了OLD记录，而NEW未定义。因此，在代码中，检查触发器是否作为DELETE或INSERT（变量TG_OP）运行，并访问相应的记录。

此外，您可以完全不进行计数，就像这样：

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" FOR EACH ROW
EXECUTE PROCEDURE aktualizujIloscPodan();

- Maxim Sloyko

---

好的，也许我不需要计数...修改了我的代码，但出现了另一个错误。你能帮忙吗？有两个问题：它不允许返回NULL（没有返回就可以工作），而且应该是ELSIF而不是ELIF。 - Miko Kronn

@Miko 抱歉，我没有检查它。已编辑。 - Maxim Sloyko

@Miko 触发器后不需要返回值。 - Maxim Sloyko

哦，我明白了。这是关于返回值的问题...但我仍然收到“old未定义”的消息？为什么？ - Miko Kronn