PostgreSQL 继承表始终返回具有 Null 值的行

Question

我指的是 http://www.if-not-true-then-false.com/2009/11/howto-create-postgresql-table-partitioning-part-1/

要重现该问题，这里是遵循一些简单的步骤：

(1) 创建名为“tutorial”的数据库

(2) 执行以下 SQL 查询：

CREATE TABLE impressions_by_day (
    advertiser_id SERIAL NOT NULL,
    day DATE NOT NULL DEFAULT CURRENT_DATE,
    impressions INTEGER NOT NULL,
        PRIMARY KEY (advertiser_id, day)
);

CREATE OR REPLACE FUNCTION insert_table()
  RETURNS void AS
$BODY$DECLARE
    _impressions_by_day impressions_by_day;
BEGIN
    INSERT INTO impressions_by_day(impressions ) VALUES(888) RETURNING  * INTO _impressions_by_day;

    RAISE NOTICE 'After insert, the returned advertiser_id is %', _impressions_by_day.advertiser_id;
END;$BODY$
  LANGUAGE 'plpgsql' VOLATILE;
ALTER FUNCTION insert_table() OWNER TO postgres;

(3) 创建名为“tutorial_partition”的数据库

(4) 执行以下 SQL 查询：

CREATE TABLE impressions_by_day (
    advertiser_id SERIAL NOT NULL,
    day DATE NOT NULL DEFAULT CURRENT_DATE,
    impressions INTEGER NOT NULL,
        PRIMARY KEY (advertiser_id, day)
);

CREATE OR REPLACE FUNCTION insert_table()
  RETURNS void AS
$BODY$DECLARE
    _impressions_by_day impressions_by_day;
BEGIN
    INSERT INTO impressions_by_day(impressions ) VALUES(888) RETURNING  * INTO _impressions_by_day;

    RAISE NOTICE 'After insert, the returned advertiser_id is %', _impressions_by_day.advertiser_id;
END;$BODY$
  LANGUAGE 'plpgsql' VOLATILE;
ALTER FUNCTION insert_table() OWNER TO postgres;

CREATE TABLE impressions_by_day_y2010m1ms2 (
    PRIMARY KEY (advertiser_id, day), 
    CHECK ( day >= DATE '2010-01-01' AND day < DATE '2010-03-01' )
) INHERITS (impressions_by_day);


CREATE INDEX impressions_by_day_y2010m1ms2_index ON impressions_by_day_y2010m1ms2 (day);


CREATE OR REPLACE FUNCTION impressions_by_day_insert_trigger()
RETURNS TRIGGER AS $$
BEGIN
    IF ( NEW.day >= DATE '2010-01-01' AND NEW.day < DATE '2010-03-01' ) THEN 
        INSERT INTO impressions_by_day_y2010m1ms2 VALUES (NEW.*); 
    ELSE
        RAISE EXCEPTION 'Date out of range.  Something wrong with the impressions_by_day_insert_trigger() function!';
    END IF;
    RETURN NULL;
END;
$$
LANGUAGE plpgsql;

CREATE TRIGGER insert_impressions_by_day_trigger 
    BEFORE INSERT ON impressions_by_day 
    FOR EACH ROW EXECUTE PROCEDURE impressions_by_day_insert_trigger();

(5) 执行

SELECT * FROM insert_table() on tutorial

我们得到

通知：插入后，返回的advertiser_id为1

(6) 执行

SELECT * FROM insert_table() on tutorial_partition

我们得到

通知：插入后，返回的advertisement_id为

1 在tutorial_partition中，怎么可能让advertisement_id也为1？

Answer 1

触发器传回 NULL，这向 INSERT 指示不执行任何操作。由于未执行任何操作，因此 RETURNING * 子句不返回任何内容。您将无法拦截（并覆盖） INSERT 并在同一操作中使用 RETURNING 并获得任何有意义的内容。