Question

我正在尝试创建一种机制，每次在它们上面调用insert命令时都会截断表。

首先，我尝试创建一个获取行数组并在插入表之前截断表的函数：

CREATE OR REPLACE FUNCTION insert_customers(customers customer[])
    RETURNS VOID AS 
$$  
BEGIN
    TRUNCATE TABLE Customers;
    INSERT INTO Customers (CustomerID, CustomerName) SELECT * FROM UNNEST(customers::Customer[]);
END
$$
LANGUAGE plpgsql;

Customer是用户定义的类型，表示Customers表中的行：

CREATE TYPE Customer AS (
  customerid VARCHAR(100),
  customername VARCHAR(100));

当我从psql调用函数时，这很有效：

SELECT * FROM insert_customers(ARRAY[ROW('ID1', 'Name1'),ROW('ID2', 'Name2')]::Customer[]);

但我还没有找到一种方法从我的java代码中执行这个插入：

String[][] customers = new String[2][];
customers[0] = new String[] { "ID1", "Name1" };
customers[1] = new String[] { "ID2", "Name2" };    

Array sqlArray = connection.createArrayOf("customer", customers);    

CallableStatement cstmt = connection.prepareCall("{ call insert_customers(?) }");
cstmt.setArray(1, sqlArray);
cstmt.execute();

创建了以下声明：

select * from insert_customers ('{{"ID1", "Name1"},{"ID2", "Name2"}}') as result

并抛出以下异常：

org.postgresql.util.PSQLException: ERROR: malformed record literal: "ID1"\n Detail: Missing left parenthesis.

然后我尝试创建一个触发器，它将在insert事件上截断表：

CREATE TRIGGER on_insert_customers
    BEFORE INSERT ON Customers
    EXECUTE PROCEDURE truncate_customers();

truncate_customers 是：

CREATE OR REPLACE FUNCTION truncate_customers()
    RETURNS TRIGGER AS 
$$  
BEGIN
    TRUNCATE TABLE Customers;   
END
$$
LANGUAGE plpgsql;

这引发了例外：

cannot TRUNCATE "customers" because it is being used by active queries in this session

任何想法???

Answer 1

修改功能

查询文本数组中不需要的元素对：

select cols[1], cols[2]
from (
    select (ordinality- 1)/2, array_agg(unnest) cols
    from unnest('{"id1", "name1", "id2", "name2"}'::text[]) with ordinality
    group by 1
    ) s

 cols | cols  
------+-------
 id1  | name1
 id2  | name2
(2 rows)

在函数中使用它，以便它可以将文本数组作为参数：

create or replace function insert_customers(text[])
returns void language plpgsql as $$  
begin
    truncate table customers;
    insert into customers (customerid, customername)
    select cols[1], cols[2]
    from (
        select (ordinality- 1)/2, array_agg(unnest) cols
        from unnest($1) with ordinality
        group by 1
        ) s;
end $$;

select insert_customers('{"id1", "name1", "id2", "name2"}');

修改触发功能

您不能在触发器中截断表，但可以删除所有行：

...
    delete from Customers;
    return new;
...

在postgres中插入之前截断表

1 个答案:

修改功能

修改触发功能