如何动态执行PostgreSQL RAISE命令 [英] How to execute PostgreSQL RAISE command dynamically

问题描述

如果满足某些条件，如何引发PostgreSQL SQL语句的错误？

我尝试过下面的代码，但出现错误。

How to raise error from PostgreSQL SQL statement if some condition is met?
I tried code below but got error.

CREATE OR REPLACE FUNCTION "exec"(text)
  RETURNS text AS
$BODY$ 
    BEGIN 
      EXECUTE $1; 
      RETURN $1; 
    END; 
$BODY$
  LANGUAGE plpgsql VOLATILE;

-- ERROR:  syntax error at or near "raise"
-- LINE 1: raise 'test' 

SELECT exec('raise ''test'' ') WHERE TRUE

在实际应用中 TRUE 被某些条件所替代。

In real application TRUE is replaced by some condition.

更新

我试图扩展答案传递异常消息参数。
尝试下面的代码，但语法错误。
如何传递消息参数？

I tried to extend answer to pass exception message parameters. Tried code below but got syntax error. How to pass message parameters ?

CREATE OR REPLACE FUNCTION exec(text, variadic ) 
  RETURNS void LANGUAGE plpgsql AS 
$BODY$  
BEGIN  
   RAISE EXCEPTION  $1, $2;  
END;  
$BODY$; 

SELECT exec('Exception Param1=% Param2=%', 'param1', 2 ); 

推荐答案

您无法调用 RAISE 在PL / pgSQL中动态（使用 EXECUTE ） - 仅适用于SQL语句， RAISE 是一个PL / pgSQL命令。

You cannot call RAISE dynamically (with EXECUTE) in PL/pgSQL - that only works for SQL statements, and RAISE is a PL/pgSQL command.

使用这个简单的函数：

CREATE OR REPLACE FUNCTION f_exec(text)
  RETURNS void LANGUAGE plpgsql AS
$BODY$ 
BEGIN 
   RAISE EXCEPTION '%', $1; 
END; 
$BODY$;

致电：

SELECT f_exec('My message is empty!');

我在这个相关答案dba.SE ：功能调用等的功能说明，链接，更多选项，上下文（包括行号）

I wrote more in this related answer on dba.SE: explanation, links, more options for the function, context (including line number) from the function call etc.

CREATE OR REPLACE FUNCTION f_exec1(VARIADIC text[]) 
  RETURNS void LANGUAGE plpgsql AS 
$BODY$  
BEGIN  
   RAISE EXCEPTION 'Reading % % %!', $1[1], $1[2], $1[3];
END;  
$BODY$; 

致电：

SELECT f_exec1('the','manual','educates');

• VARIADIC 不是数据类型，而是参数模式

  • VARIADIC is not a data type, but an argument mode.

    元素必须像任何其他数组元素一样处理。

    Elements have to be handled like any other array element.

    在 RAISE 语句中使用多个变量，将多个％放入消息文本中。

    To use multiple variables in a RAISE statement, put multiple % into the message text.

    如果没有$ 3传递给调用，上述示例将失败。您必须从可变数量的输入元素组合一个字符串。示例：

    The above example will fail if no $3 is passed to the call. You'd have to assemble a string from the variable number of input elements. Example:

    CREATE OR REPLACE FUNCTION f_exec2(VARIADIC _arr text[]) 
      RETURNS void LANGUAGE plpgsql AS 
    $BODY$  
    DECLARE
       _msg text := array_to_string(_arr, ' and '); -- simple string construction
    BEGIN  
       RAISE EXCEPTION 'Reading %!', _msg;
    END;  
    $BODY$; 
    

    致电：

    SELECT f_exec2('the','manual','educates');
    

    我怀疑你需要一个 VARIADIC 参数这一切。请阅读此处的手册 。
    
    相反，定义所有参数，也可以添加默认值：

    I doubt you need a VARIADIC parameter for this at all. Read the manual here.
    Instead, define all parameters, maybe add defaults:

    CREATE OR REPLACE FUNCTION f_exec3(_param1 text = ''
                                      ,_param2 text = ''
                                      ,_param3 text = 'educates') 
      RETURNS void LANGUAGE plpgsql AS 
    $BODY$  
    BEGIN  
       RAISE EXCEPTION 'Reading % % %!', $1, $2, $3;
    END;  
    $BODY$; 
    

    致电：

    SELECT f_exec3('the','manual','educates');
    SELECT f_exec3();  -- defaults kick in
    

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