从本地现有类型指定dblink列定义列表

Question

我正在使用dblink在数据库之间移动某些数据.一切都是保存和声音,但我想知道是否有更方便的方法来定义dblink查询结果的列定义列表.我可以这样做:

SELECT *
FROM dblink('dbname=remote', 'select * from test')
AS t1(id integer, data text); 

我正在与之交互的表在两个数据库(远程和本地)中具有相同的模式定义.我想的是:

SELECT *
FROM dblink('dbname=remote', 'select * from test')
AS t1 LIKE public.test; 

要么:

SELECT *
FROM dblink('dbname=remote', 'select * from test')
AS t1::public.test;

列定义列表往往变得很长.有什么我可能忽略的吗？

编辑:

在我创建一个小函数作为解决方法之前,这对我来说是一个问题.

CREATE OR REPLACE FUNCTION dblink_star_func(_conn text, _schema_name text, _table_name text)
RETURNS text
LANGUAGE PLPGSQL
VOLATILE STRICT
AS $function$
    DECLARE       
        _dblink_schema text;
        _cols          text; 
        _q             text;
        _func_name     text := format('star_%s', $3);
        _func          text;        
    BEGIN
        SELECT nspname INTO _dblink_schema
        FROM pg_namespace n, pg_extension e
        WHERE e.extname = 'dblink' AND e.extnamespace = n.oid;

        SELECT array_to_string(array_agg(column_name || ' ' || udt_name), ', ') INTO _cols
        FROM information_schema.columns
        WHERE table_schema = $2 AND table_name = $3;

        _q := format('SELECT * FROM %I.dblink(%L, %L) AS remote (%s)',
            _dblink_schema,
            _conn,
            format('SELECT * FROM %I.%I', $2, $3),
            _cols
        );

        _func := $_func$
            CREATE OR REPLACE FUNCTION %s()
            RETURNS SETOF %I.%I
            LANGUAGE SQL
            VOLATILE STRICT
            AS $$ %s; $$
        $_func$;

        EXECUTE format(_func, _func_name, $2, $3, _q);

        RETURN _func_name;
    END;
$function$;

此函数创建并生成一个包装dblink调用的函数.它肯定不是为了繁重而是方便.如果事实证明它根本不是必要的话会很好.

> select dblink_star_func('dbname=ben', 'public', 'test');
????????????????????
? dblink_star_func ?
????????????????????
? star_test        ?
????????????????????
(1 row)

> select * from star_test() where data = 'success';
????????????????
? id ?  data   ?
????????????????
?  1 ? success ?
????????????????
(1 row)

Answer 1

尝试这样的事情:

select (rec).* from dblink('dbname=...','select myalias from foreign_table
  myalias') t1 (rec local_type)

示例(从其他数据库获取表统计信息):

select (rec).* from dblink('dbname=foreignDb','select t1 from
  pg_stat_all_tables t1') t2 (rec pg_stat_all_tables)

Answer 2

您可能需要确保您的类型始终同步，但这应该有效：

SELECT (t1::test).* 
  FROM dblink('dbname=remote', 'select * from test') AS t1;

关键是您通常需要括号来确保解析器知道您正在处理元组。

例如这对我有用：

 CREATE TABLE test (id int, test bool);
 select (t1::test).* from (select 1, true) t1;

但这会引发语法错误：

 select t1::test.* from (select 1, true) t1;