Postgresql 9.2 中在查询中调用函数的正确方法

Posted 2023-03-31

【中文标题】Postgresql 9.2 中在查询中调用函数的正确方法

【英文标题】：Correct way in Postgresql 9.2 to call a function in a query

【发布时间】：2014-03-13 18:08:05

【问题描述】：

我今天注意到我的日志文件有些奇怪。我看到一个“通知”被一遍又一遍地登录。而且我想我已经找到了原因，但不理解它或解决方法。

查询是：

select (get_account_details(account.id)).* from account where id in (113126123254, 116261470380);

get_account_details 将在某些情况下记录一条消息 - 一种情况是帐户具有 daily_spend_limit。在我的日志中我看到：

NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 116261470380 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00
NOTICE:  Account 113126123254 has a daily_spend_limit of 10.00.  Remaining balance as been calculated as 10.00

莫名其妙，但我终于注意到它被调用了 17 次 where account.这是帐户表中的确切列数。

如果我跑：

select * from get_account_details(113126123254);

我只记录了 1 条通知。

这里发生了什么以及我如何“正确”编写此查询？

【参考方案1】：

我不明白为什么更简单的构造会为每一列调用一次函数，但这是抑制它的一种方法：

select (get_account_details).* from 
(
    select get_account_details(account.id) from account 
         where id in (113126123254, 116261470380)
) foo

由于您无法重现，而且我手边没有您的架构，所以让我从头开始创建架构：

create table foo (id integer, a text, b text, c text, d text, e text);
insert into foo (id) select * from generate_series(1,4);
create function get_foo(int) returns setof foo as $$ BEGIN 
    RAISE NOTICE 'dfjkl'; 
    return query select * from foo where id=$1; 
END $$ language plpgsql;

现在执行这些，第一个给出 12 NOTICE，第二个给出 2。

select (get_foo(id)).* from foo where id in (1,2);
select (get_foo).* from (select get_foo(id) from foo where id in (1,2)) ssss;

【讨论】：

我刚刚测试了您的解决方案，得到了相同的日志输出。