(注意:更新了下面采用的答案。)
对于 PostgreSQL 8.1(或更高版本)分区表,如果 UPDATE
意味着对定义分区隔离的约束字段的更改?
例如,我有一个表记录,分为事件记录和非事件记录,如下所示:
create table RECORDS (RECORD varchar(64) not null, ACTIVE boolean default true);
create table ACTIVE_RECORDS ( check (ACTIVE) ) inherits RECORDS;
create table INACTIVE_RECORDS ( check (not ACTIVE) ) inherits RECORDS;
INSERT
触发器和函数运行良好:新的事件记录放入一个表中,新的非事件记录放入另一个表中。我希望对 ACTIVE 字段进行 UPDATE
以将记录从一个后代表“移动”到另一个后代表,但是我遇到了一个错误,表明这可能是不可能的。
触发器规范和错误消息:
pg=> CREATE OR REPLACE FUNCTION record_update()
RETURNS TRIGGER AS $$
BEGIN
IF (NEW.active = OLD.active) THEN
RETURN NEW;
ELSIF (NEW.active) THEN
INSERT INTO active_records VALUES (NEW.*);
DELETE FROM inactive_records WHERE record = NEW.record;
ELSE
INSERT INTO inactive_records VALUES (NEW.*);
DELETE FROM active_records WHERE record = NEW.record;
END IF;
RETURN NULL;
END;
$$
LANGUAGE plpgsql;
pg=> CREATE TRIGGER record_update_trigger
BEFORE UPDATE ON records
FOR EACH ROW EXECUTE PROCEDURE record_update();
pg=> select * from RECORDS;
record | active
--------+--------
foo | t -- 'foo' record actually in table ACTIVE_RECORDS
bar | f -- 'bar' record actually in table INACTIVE_RECORDS
(2 rows)
pg=> update RECORDS set ACTIVE = false where RECORD = 'foo';
ERROR: new row for relation "active_records" violates check constraint "active_records_active_check"
使用触发器过程(返回 NULL 等)向我表明在调用触发器之前检查约束并引发错误,这意味着我当前的方法将不起作用。这可以开始工作吗?
附加答案
pg 的[列表分区][2] 似乎是完成此任务的最简单方法:
-- untested!
create table RECORDS (..., ACTIVE boolean...)
partition by list(ACTIVE) (
partition ACTIVE_RECORDS values (true),
partition INACTIVE_RECORDS values (false)
)
更新/回答
下面是我最终使用的 UPDATE
触发过程,分配给每个分区的相同过程。完全归功于Bell ,他的回答给了我触发分区的关键见解:
CREATE OR REPLACE FUNCTION record_update()
RETURNS TRIGGER AS $$
BEGIN
IF ( (TG_TABLE_NAME = 'active_records' AND NOT NEW.active)
OR
(TG_TABLE_NAME = 'inactive_records' AND NEW.active) ) THEN
DELETE FROM records WHERE record = NEW.record;
INSERT INTO records VALUES (NEW.*);
RETURN NULL;
END IF;
RETURN NEW;
END;
$$
LANGUAGE plpgsql;
最佳答案
它可以工作,只需要为每个分区定义执行移动的触发器,而不是整个表。因此,像您对表定义和 INSERT 触发器所做的那样开始
CREATE TABLE records (
record varchar(64) NOT NULL,
active boolean default TRUE
);
CREATE TABLE active_records (CHECK (active)) INHERITS (records);
CREATE TABLE inactive_records (CHECK (NOT active)) INHERITS (records);
CREATE OR REPLACE FUNCTION record_insert()
RETURNS TRIGGER AS $$
BEGIN
IF (TRUE = NEW.active) THEN
INSERT INTO active_records VALUES (NEW.*);
ELSE
INSERT INTO inactive_records VALUES (NEW.*);
END IF;
RETURN NULL;
END;
$$
LANGUAGE plpgsql;
CREATE TRIGGER record_insert_trigger
BEFORE INSERT ON records
FOR EACH ROW EXECUTE PROCEDURE record_insert();
...让我们来一些测试数据...
INSERT INTO records VALUES ('FirstLittlePiggy', TRUE);
INSERT INTO records VALUES ('SecondLittlePiggy', FALSE);
INSERT INTO records VALUES ('ThirdLittlePiggy', TRUE);
INSERT INTO records VALUES ('FourthLittlePiggy', FALSE);
INSERT INTO records VALUES ('FifthLittlePiggy', TRUE);
现在分区上的触发器。 if NEW.active = OLD.active 检查隐含在检查 active 的值中,因为我们首先知道表中允许的内容。
CREATE OR REPLACE FUNCTION active_partition_constraint()
RETURNS TRIGGER AS $$
BEGIN
IF NOT (NEW.active) THEN
INSERT INTO inactive_records VALUES (NEW.*);
DELETE FROM active_records WHERE record = NEW.record;
RETURN NULL;
ELSE
RETURN NEW;
END IF;
END;
$$
LANGUAGE plpgsql;
CREATE TRIGGER active_constraint_trigger
BEFORE UPDATE ON active_records
FOR EACH ROW EXECUTE PROCEDURE active_partition_constraint();
CREATE OR REPLACE FUNCTION inactive_partition_constraint()
RETURNS TRIGGER AS $$
BEGIN
IF (NEW.active) THEN
INSERT INTO active_records VALUES (NEW.*);
DELETE FROM inactive_records WHERE record = NEW.record;
RETURN NULL;
ELSE
RETURN NEW;
END IF;
END;
$$
LANGUAGE plpgsql;
CREATE TRIGGER inactive_constraint_trigger
BEFORE UPDATE ON inactive_records
FOR EACH ROW EXECUTE PROCEDURE inactive_partition_constraint();
...并测试结果...
scratch=> SELECT * FROM active_records;
record | active
------------------+--------
FirstLittlePiggy | t
ThirdLittlePiggy | t
FifthLittlePiggy | t
(3 rows)
scratch=> UPDATE records SET active = FALSE WHERE record = 'ThirdLittlePiggy';
UPDATE 0
scratch=> SELECT * FROM active_records;
record | active
------------------+--------
FirstLittlePiggy | t
FifthLittlePiggy | t
(2 rows)
scratch=> SELECT * FROM inactive_records;
record | active
-------------------+--------
SecondLittlePiggy | f
FourthLittlePiggy | f
ThirdLittlePiggy | f
(3 rows)
关于PostgreSQL:更新意味着跨分区移动,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1798209/