更新语句级别触发器后，PostgreSQL OLD 无法正常工作

Question

我正在尝试通过课程的课程分数总和来更新课程分数。如果我像这样 select 特定课程 ID，它会完美地工作：

BEGIN   

UPDATE course
SET points = (SELECT COALESCE(SUM("lesson"."points"), 0) AS "sum_points" FROM "course" LEFT OUTER JOIN "lesson" ON ("course"."id" = "lesson"."course_id") WHERE "course"."id" = 7) 
WHERE "course"."id" = 7;
RETURN NULL;
                
END;

但不适用于更新实例 OLD。我想更新正在更新的课程的积分。

BEGIN   

UPDATE course
SET points = (SELECT COALESCE(SUM("lesson"."points"), 0) AS "sum_points" FROM "course" LEFT OUTER JOIN "lesson" ON ("course"."id" = "lesson"."course_id") WHERE "course"."id" = OLD."course_id")
WHERE "course"."id" = OLD."course_id";
RETURN NULL;
            
END;

我正在使用 django-pgtriggers：https://pypi.org/project/django-pgtrigger/

@pgtrigger.register(
    pgtrigger.Trigger(
        name="add_course_point",
        level=pgtrigger.Statement,
        when=pgtrigger.After,
        operation=pgtrigger.Update,
        func=f"""
            UPDATE course
            SET points = (SELECT COALESCE(SUM("lesson"."points"), 0) AS "sum_points" FROM "course" LEFT OUTER JOIN "lesson" ON ("course"."id" = "lesson"."course_id") WHERE "course"."id" = OLD."course_id")
            WHERE "course"."id" = OLD."course_id";
            RETURN NULL;
            """
    )
)

Answer 1

OLD 和 NEW 在 Statement level 的情况下总是 NULL。

将level=pgtrigger.Statement替换为level=pgtrigger.Row

@pgtrigger.register(
    pgtrigger.Trigger(
        name="add_course_point",
        level=pgtrigger.Row,
        when=pgtrigger.After,
        operation=pgtrigger.Update,
        func=f"""
            UPDATE course
            SET points = (SELECT COALESCE(SUM("lesson"."points"), 0) AS "sum_points" FROM "course" LEFT OUTER JOIN "lesson" ON ("course"."id" = "lesson"."course_id") WHERE "course"."id" = OLD."course_id")
            WHERE "course"."id" = OLD."course_id";
            RETURN NULL;
            """
    )
)

或者添加referencing=pgtrigger.Referencing(old='old_table_name')然后修改你的函数。

Answer 2

我已经注册了 2 个触发器。第一个是 before update 触发插入课程。第二个是 after update 触发更新和删除的课程。 课程分数增加或减少总和课分毕竟。

@pgtrigger.register(
        pgtrigger.Trigger(
        name="add_course_point",
        operation=pgtrigger.Insert,
        level=pgtrigger.Row,
        when=pgtrigger.Before,
        func=f"""
            UPDATE course
            SET points = (points + NEW.points)
            WHERE "course"."id" = NEW.course_id;
            RETURN NEW;
            """,
    ),
    pgtrigger.Trigger(
        name="update_course_point",
        operation=(pgtrigger.Update | pgtrigger.Delete),
        level=pgtrigger.Row,
        when=pgtrigger.After,
        func=f"""
            UPDATE course
            SET points = (SELECT COALESCE(SUM("lesson"."points"), 0) AS "sum_points" FROM "course" LEFT OUTER JOIN "lesson" ON ("course"."id" = "lesson"."course_id") WHERE "course"."id" = OLD.course_id)
            WHERE "course"."id" = OLD.course_id;
            RETURN NULL;
            """,
    ),
)

更新语句级别触发器后，PostgreSQL OLD 无法正常工作

PostgreSQL OLD not working in after update statement level trigger

python

django

postgresql

triggers

postgresql-triggers