如何在 postgres 函数中使用 EXECUTE FORMAT ... USING [英] How to use EXECUTE FORMAT ... USING in postgres function

问题描述

CREATE OR REPLACE FUNCTION dummytest_insert_trigger()
  RETURNS trigger AS
$BODY$
DECLARE
v_partition_name    VARCHAR(32);
        BEGIN
        IF NEW.datetime IS NOT NULL THEN
                v_partition_name := 'dummyTest';            
                EXECUTE format('INSERT INTO %I VALUES ($1,$2)',v_partition_name)using NEW.id,NEW.datetime;              
                END IF;                    
           RETURN NULL;
        END;
        $BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;
ALTER FUNCTION dummytest_insert_trigger()
  OWNER TO postgres;

我正在尝试使用插入 dummyTest 值(1,'2013-01-01 00:00:00+05:30');

I'm trying to insert using insert into dummyTest values(1,'2013-01-01 00:00:00+05:30');

但它显示错误为

ERROR: function format(unknown) does not exist
SQL state: 42883
Hint: No function matches the given name and argument types. You might need to add explicit type casts.
Context: PL/pgSQL function "dummytest_insert_trigger" line 8 at EXECUTE statement

我无法得到错误.

推荐答案

您的函数在 Postgres 9.0 或更高版本中可能如下所示:

Your function could look like this in Postgres 9.0 or later:

CREATE OR REPLACE FUNCTION dummytest_insert_trigger()
  RETURNS trigger AS
$func$
DECLARE
   v_partition_name text := quote_ident('dummyTest');  -- assign at declaration
BEGIN
   IF NEW.datetime IS NOT NULL THEN
      EXECUTE 
      'INSERT INTO ' || v_partition_name || ' VALUES ($1,$2)'
      USING NEW.id, NEW.datetime;              
   END IF;                    

   RETURN NULL;  -- You sure about this?
END
$func$  LANGUAGE plpgsql;

关于RETURN NULL:

• 在 PostgreSQL 触发前忽略结果?

我建议不要使用混合大小写标识符.使用 format( .. %I ..) 或 quote_ident()，您会得到一个名为 "dummyTest" 的表，您可以使用它在其存在的其余部分中，我必须双引号.相关:

I would advice not to use mixed case identifiers. With format( .. %I ..) or quote_ident(), you'd get a table named "dummyTest", which you'll have to double quote for the rest of its existence. Related:

• PostgreSQL 列名是否区分大小写?

改用小写:

quote_ident('dummytest')

只要您有一个静态表名，就没有必要将动态 SQL 与 EXECUTE 一起使用.但这可能只是简化的示例?

There is really no point in using dynamic SQL with EXECUTE as long as you have a static table name. But that's probably just the simplified example?

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