Question

我想知道PostgreSQL中是否有可能循环遍历当前函数的所有可用输入参数，并将这些参数（key =＆gt; value）附加到hstore变量。

hstore-key =给定输入参数/参数的名称....
hstore-Value =给定参数的值......

例如：

-- input for call function with input arguments
SELECT append_hstore_from_args ('val1','val22','val333');

CREATE OR REPLACE FUNCTION append_hstore_from_args (IN param1 text, IN param2 text, IN param3 text)
RETURNS text AS
$BODY$ 
DECLARE   
new_h hstore;    
BEGIN
-- below is pseudo
for p in all_params
loop 
    new_h := new_h+"$p->name"=>"$p->value";
end loop;

-- at this point the variable new_h (hstore) should contain 
-- '"param1"=>"val1","param2"=>"val22","param3"=>"val333"'

-- call function with hstore argument
perform test.func123(new_h);

RETURN;
END;
$BODY$
LANGUAGE plpgsql VOLATILE SECURITY DEFINER

我已经搜索过，但遗憾的是没有找到任何有关如何在PostgreSQL中完成此操作的提示。

Answer 1

我认为这是一个如何处理variable number of function arguments的问题。

变量参数可以作为数组在函数内部访问。您可以使用FOREACH ... LOOP：

create or replace function strings_to_hstore(args variadic text[])
returns hstore language plpgsql as $$
declare
    idx int = 0;
    str text;
    hst hstore;
    res hstore = '';
begin
    foreach str in array args loop
        idx:= idx+ 1;
        execute format($f$select 'param%s=>%s'$f$, idx, str) into hst;
        res:= res|| hst;
    end loop;
    return res;
end $$;

select strings_to_hstore('one', 'two');

            strings_to_hstore         
----------------------------------
 "param1"=>"one", "param2"=>"two"
(1 row)

select strings_to_hstore('red', 'green', 'blue');

                  strings_to_hstore                   
------------------------------------------------------
 "param1"=>"red", "param2"=>"green", "param3"=>"blue"
(1 row)

如果要在参数列表中定义hstore键：

create or replace function strings_with_keys_to_hstore(args variadic text[])
returns hstore language plpgsql as $$
declare
    idx int = 0;
    key text;
    str text;
    hst hstore;
    res hstore = '';
begin
    foreach str in array args loop
        idx:= idx+ 1;
        if idx & 1 then
            key:= str;
        else
            execute format($f$select '%s=>%s'$f$, key, str) into hst;
            res:= res|| hst;
        end if;
    end loop;
    return res;
end $$;

select strings_with_keys_to_hstore('key1', 'val1', 'key2', 'val2');

  strings_with_keys_to_hstore   
--------------------------------
 "key1"=>"val1", "key2"=>"val2"
(1 row)

请注意，有standard hstore functions：hstore(text[])和hstore(text[], text[])。

Postgresql函数循环通过输入参数并附加到hstore

1 个答案: