(Note: updated with adopted answer below.)
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受约束字段进行更改,如何定义UPDATE
触发器和将记录从一个分区"移动"到另一个分区的过程?
例如,我将表记录划分为活动记录和非活动记录,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:新的活动记录放在一个表中,新的非活动记录放在另一个表中.我希望将UPDATE
s移动到活动字段,以便将记录从一个子代表"移动"到另一个子代表,但我遇到了一个错误,这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)向我建议在调用触发器之前判断约束并引发错误,这意味着我当前的方法无法工作.这能起作用吗?
UPDATE/ANSWER
下面是我最后使用的UPDATE
触发器过程,与分配给每个分区的过程相同.完全归功于Bell,他的回答让我对分区有了关键的了解:
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;