如何修复重复的键值违反 Postges 9+ 中的唯一约束错误

如何解决如何修复重复的键值违反 Postges 9+ 中的唯一约束错误

有时会出现奇怪的重复键错误

duplicate key value violates unique constraint "session_pkey"
Key (workplace)=(WIN-N9BSKUNKBC8 ) already exists.

发生在脚本中：

delete from session where workplace='WIN-N9BSKUNKBC8' ;
INSERT INTO session (workplace,ipaddress,logintime,loggeduser)
SELECT 'WIN-N9BSKUNKBC8',inet_client_addr()::CHAR(14),current_timestamp::CHAR(28),CURRENT_USER WHERE NOT EXISTS (SELECT 1 FROM session WHERE workplace='WIN-N9BSKUNKBC8' )

Sript 每 10 分钟运行一次窗体 Windows 任务调度程序。错误只是偶尔发生。

如何解决这个问题？表定义为

CREATE TABLE public.session
(
    loggeduser character(10),workplace character(16) NOT NULL,ipaddress character(20),logintime character(28),activity timestamp with time zone,CONSTRAINT session_pkey PRIMARY KEY (workplace)
)

环境：

Postgresql 13.1,compiled by Visual C++ build 1914,64-bit
Windows server 2019
psqlODBC driver 13.00.0000

解决方法

您可以使用on conflict：

INSERT INTO session (workplace,ipaddress,logintime,loggeduser)
    SELECT 'WIN-N9BSKUNKBC8',inet_client_addr()::CHAR(14),current_timestamp::CHAR(28),CURRENT_USER 
    ON CONFLICT DO NOTHING;

鉴于您只有一行进入，我猜测问题是由于并发问题。