在我们的数据库中,我们有一个表,其中记录由来自大约4个其他表的id引用。这些'子'表具有'master'表的外键,'on delete set null'。所有表都有一个mutating-tables系统(即:包含plsql-table的包,在从after语句触发器调用过程时处理记录)。 但是,在删除master-table中的记录时,子记录会给出'table is mutating'错误。我发现有点奇怪,因为外键似乎触发了一些隐含的update-statement,它位于plsql-table中。
我所追求的只是试图找到原因,我似乎无法挖掘一些相关信息! 当然,我们确实有一个解决方案,只需在关联表中将引用的id字段设置为null,从master的after语句触发器开始,但我仍然想知道为什么会发生这种情况。
重现错误的代码:
CREATE TABLE master_table (ID NUMBER(5) NOT NULL);
CREATE TABLE child_table (ID NUMBER(5) NOT NULL, master_id NUMBER(5));
alter table master_table add constraint master_pk primary key (ID);
alter table child_table add constraint child_pk primary key (ID);
ALTER TABLE child_table
add constraint on_delete_master foreign key (master_id)
references master_table (ID) on delete set null;
CREATE OR REPLACE PACKAGE pkg_child
IS
PROCEDURE init_temp;
PROCEDURE add_temp(i_action IN VARCHAR2,
i_master_old IN child_table.master_id%TYPE,
i_master_new IN child_table.master_id%TYPE);
PROCEDURE process_temp;
END;
/
CREATE OR REPLACE PACKAGE BODY pkg_child IS
TYPE temp_record IS RECORD(
action VARCHAR2(1),
old_master_id child_table.master_id%TYPE,
new_master_id child_table.master_id%TYPE);
TYPE type_temp IS TABLE OF temp_record INDEX BY BINARY_INTEGER;
tab_temp type_temp;
PROCEDURE init_temp IS
BEGIN
tab_temp.delete;
END;
PROCEDURE add_temp(i_action IN VARCHAR2,
i_master_old IN child_table.master_id%TYPE,
i_master_new IN child_table.master_id%TYPE) IS
v_id BINARY_INTEGER;
BEGIN
v_id := nvl(tab_temp.last, 0) + 1;
tab_temp(v_id).action := i_action;
tab_temp(v_id).old_master_id := i_master_old;
tab_temp(v_id).new_master_id := i_master_new;
END;
PROCEDURE process_temp IS
v_id BINARY_INTEGER;
v_total NUMBER;
BEGIN
v_id := tab_temp.first;
WHILE v_id IS NOT NULL LOOP
IF tab_temp(v_id).action = 'U' THEN
SELECT COUNT(1)
INTO v_total
FROM child_table;
END IF;
v_id := tab_temp.next(v_id);
END LOOP;
END;
END;
/
CREATE OR REPLACE TRIGGER child_table_bs
BEFORE
INSERT OR UPDATE OR DELETE
ON child_table
REFERENCING OLD AS OLD NEW AS NEW
BEGIN
pkg_child.init_temp;
END;
/
CREATE OR REPLACE TRIGGER child_table_ar
AFTER
INSERT OR DELETE OR UPDATE
ON child_table
REFERENCING OLD AS OLD NEW AS NEW
FOR EACH ROW
DECLARE
v_action VARCHAR2(1);
BEGIN
IF inserting THEN
v_action := 'I';
ELSIF updating THEN
v_action := 'U';
ELSIF deleting THEN
v_action := 'D';
END IF;
pkg_child.add_temp(v_action, :old.id, :new.id);
END;
/
CREATE OR REPLACE TRIGGER child_table_as
AFTER
INSERT OR UPDATE OR DELETE
ON child_table
REFERENCING OLD AS OLD NEW AS NEW
BEGIN
pkg_child.process_temp;
END;
/
INSERT ALL
INTO master_table (id) VALUES (1)
INTO master_table (id) VALUES (2)
INTO master_table (id) VALUES (3)
INTO master_table (id) VALUES (4)
SELECT * FROM dual;
INSERT ALL
INTO child_table (id, master_id) VALUES (1, NULL)
INTO child_table (id, master_id) VALUES (2, 1)
INTO child_table (id, master_id) VALUES (3, 2)
INTO child_table (id, master_id) VALUES (4, NULL)
SELECT * FROM dual;
-- error on this delete: mutating tables
-- why?
DELETE FROM master_table
WHERE id = 2;
清理代码:
DROP TRIGGER child_table_bs;
DROP TRIGGER child_table_ar;
DROP TRIGGER child_table_as;
DROP PACKAGE pkg_child;
DROP TABLE child_table;
DROP TABLE master_table;
由于
答案 0 :(得分:0)
您有一个语句,主表中的DELETE可能会影响多行。 由于CASCADE约束,每个已删除的行将触发CHILD表的隐式/递归UPDATE语句。也就是说,理论上你可以有多个子表的UPDATE。
说你做了DELETE FROM master_table WHERE id in (1, 2)
这将生成两个UPDATE child_table语句。其中每个都会尝试执行AFTER UPDATE触发器,因此您将获得两次
的执行SELECT COUNT(1)
INTO v_total
FROM child_table
单个DELETE语句下的任何SELECT的结果应该在特定时间点保持一致。但SELECT不会在DELETE结束时发生,而是在删除期间执行多次,每次都可能具有不同的结果。 Oracle可以计算出你想要/期望的结果,因此会抛出变异表错误。
在不了解业务需求的情况下,很难推荐解决方案。像Oracle一样,我们不知道你要做什么。可能通过在事务结束时执行的ON-COMMIT MV或DBMS_JOB来解决这种情况。