PostgreSQL：UPDATE意味着跨越分区

(注：更新为以下答案。)

对于Postgresql 8.1(或更高版本)分区表，如何定义UPDATE触发器和过程以将记录从一个分区“移动”到另一个分区，如果UPDATE意味着更改限制字段来定义分区隔离？

例如，我将表记录分为活动和非活动记录，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触发器和函数工作正常：将新的活动记录放在一个表中，并将新的非活动记录放在另一个表中。我希望UPDATEs的ACTIVE字段将一个记录从一个后代表移动到另一个，但我遇到一个错误，这表明这可能是不可能的。

触发器规格和错误信息：

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"

使用触发器程序(返回NULL等)建议我检查约束，并且在调用触发器之前引发错误，这意味着我当前的方法不起作用。这可以得到工作吗？

UPDATE / ANSWER

以下是我最终使用的UPDATE触发程序，分配给每个分区的相同过程。信用完全是Bell，他的答案给了我在分区上触发的关键洞察：

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;

它可以使其工作，只需要为每个分区而不是整个表定义移动的触发器。所以就像对表定义和INSERT触发一样

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();

…让我们有一些测试数据…

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。如果NEW.active = OLD.active检查隐含在检查活动的值，因为我们知道首先允许在表中是什么。

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)

原文链接：https://www.f2er.com/postgresql/192979.html

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