我有一个简单的表,由三列组成;一个bigint,一个布尔值和一个文本。这样的事情:
CREATE SEQUENCE foo_seq;
CREATE TABLE foo (
i_foo BIGINT DEFAULT nextval('foo_seq'),
isok BOOLEAN DEFAULT TRUE,
who CHARACTER VARYING(32) NOT NULL
);
ALTER TABLE foo ADD CONSTRAINT foo_pkey PRIMARY KEY (i_foo);
CREATE RULE foo_insert AS ON INSERT TO foo DO (
DELETE FROM foo
WHERE ((foo.i_foo < NEW.i_foo) AND (NEW.who = foo.who))
);
它非常接近更新。我希望在任何插入后,表总是有一行,只是i_foo增加。
当我手动插入新项目时,它工作正常,它删除最后一项并插入新项目。换句话说,只是i_foo增加一个。
但是同样的命令在python脚本中不起作用。将删除所有实体,包括新实体。插入后表格将为空。
INSERT INTO foo (isok, who) VALUES (True, 'someone');
class adoerclass(threading.Thread):
def __init__(self, db):
self.db = db
threading.Thread.__init__(self)
self.setDaemon(True)
self.start()
def run(self):
while True:
isGood = True
try:
lock.acquire()
self.db.execute("INSERT INTO foo (isok, who) "
"VALUES (%s, %s)", [isGood, 'someone'])
self.db.commit()
lock.release()
except:
lock.release()
print("exception!")
time.sleep(RETRY_TIME)
lock.release()
我很迷惑。
最后我写了一个触发器。它工作正常
CREATE SEQUENCE foo_seq;
CREATE TABLE foo (
i_foo BIGINT DEFAULT nextval('foo_seq'),
isok BOOLEAN DEFAULT TRUE,
who CHARACTER VARYING(32) NOT NULL
);
ALTER TABLE foo ADD CONSTRAINT foo_pkey PRIMARY KEY (i_foo);
CREATE FUNCTION foo_insert_before() RETURNS trigger
LANGUAGE plpgsql
AS $$
BEGIN
DELETE FROM foo WHERE (( NEW.i_foo > foo.i_foo ) AND (NEW.who = foo.who));
RETURN NEW;
END;
$$;
CREATE TRIGGER foo_insert BEFORE INSERT ON foo FOR EACH ROW EXECUTE PROCEDURE foo_insert_before();