从PostgreSQL函数返回自定义类型

Question

从PostgreSQL函数返回自定义类型

8

我将尝试从PostgreSQL函数中返回自定义类型，具体如下：

DROP TYPE IF EXISTS GaugeSummary_GetDateRangeForGauge_Type CASCADE; -- Drop our previous type

CREATE TYPE GaugeSummary_GetDateRangeForGauge_Type AS   -- Recreate our type    
(
    Minimum timestamp without time zone,
    Maximum timestamp without time zone
);


CREATE OR REPLACE FUNCTION GaugeSummary_GetDateRangeForGauge
(
    GaugeID integer
)
RETURNS GaugeSummary_GetDateRangeForGauge_Type AS 
$$
DECLARE
    iGaugeID ALIAS FOR $1;
    oResult     GaugeSummary_GetDateRangeForGauge_Type%ROWTYPE;
BEGIN
    SELECT INTO oResult
        min(ArchivedMinimumTime) as Minimum, 
        max(TelemeteredMaximumTime) as Maximum 
    FROM GaugeSummary 
    WHERE GaugeID = $1;

    RETURN oResult;
END;
$$ LANGUAGE plpgsql;

SELECT GaugeSummary_GetDateRangeForGauge(2291308);

我遇到了两个问题。

1) - 我的结果以 "("1753-01-01 12:00:00","2009-11-11 03:45:00")"的形式返回为单列，而我需要它们以两列的形式返回。

解决！- 愚蠢的错误... 应该是SELECT * FROM GaugeSummary_GetDateRangeForGauge(123)

2) 结果是整个表中的最大值和最小值 - WHERE约束没有被使用。

例如：

GaugeSummaryID  GaugeID   ArchivedMinimumTime   TelemeteredMaximumTime
80               4491   "2009-03-28 12:00:00"   "2009-06-27 12:00:00"
81               4491   "2009-03-28 12:00:00"   "2009-06-27 12:00:00"

但是调用该函数会给我：

"1753-01-01 12:00:00", "2009-11-11 03:45:00"

谢谢！

答案2:

似乎在“LANGUAGE 'SQL' STABLE;”函数内运行相同的查询可以正常工作：

CREATE OR REPLACE FUNCTION GaugeSummary_GetDateRangeForGauge
(
    GaugeID integer
)
RETURNS GaugeSummary_GetDateRangeForGauge_Type AS
$$
    SELECT min(ArchivedMinimumTime) as Minimum, 
        max(TelemeteredMaximumTime) as Maximum 
    FROM GaugeSummary WHERE GaugeID = $1;
$$ LANGUAGE 'SQL' STABLE;

然而，知道为什么plpgsql函数不能正确工作会很好...

- Robert

1个回答

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- Arthur Thomas · Accepted Answer

我尝试了这个，当执行时我得到了两列返回结果

SELECT * GaugeSummary_GetDateRangeForGauge(1);

结果：

aadb=# select * from GaugeSummary_GetDateRangeForGauge(1);
      minimum               |          maximum
----------------------------+----------------------------
 2010-01-11 15:14:20.649786 | 2010-01-11 15:14:24.745783
(1 row)

我正在使用8.4版本并在psql中运行它。你能否澄清一下你是如何得到你的结果的？

至于第二个问题，如果你只想要结果，则从查询中删除min()和max()聚合函数。这样做将确保来自这些列的结果将返回匹配您ID的行。

更新: 好吧，我不确定发生了什么。我刚把所有类似的东西放到我的测试数据库中，它按照我期望的方式工作。

自定义类型

create type custom_type as ( 
   minimum timestamp without time zone, 
   maximum timestamp without time zone);

表格（测试）

aadb=# select * from test order by id;
 id |             a              |             b
----+----------------------------+----------------------------
  1 | 2010-01-11 17:09:52.329779 | 2010-01-11 17:09:52.329779
  1 | 2010-01-11 17:10:04.729776 | 2010-01-11 17:10:04.729776
  2 | 2010-01-11 17:09:55.049781 | 2010-01-11 17:10:21.753781
  2 | 2010-01-11 17:10:30.501781 | 2010-01-11 17:10:30.501781
  3 | 2010-01-11 17:09:58.289772 | 2010-01-11 17:09:58.289772
  3 | 2010-01-11 17:35:38.089853 | 2010-01-11 17:35:38.089853
(6 rows)

函数

create or replace function maxmin (pid integer) returns custom_type as $$ 
declare  
  oResult custom_type%rowtype; 
begin 
  select into oResult min(a) as minimum, max(b) as maximum 
  from test where id = pid; 

  return oResult; 
end; 
$$ language plpgsql;

结果

aadb=# select * from maxmin(2);
          minimum           |          maximum
----------------------------+----------------------------
 2010-01-11 17:09:55.049781 | 2010-01-11 17:10:30.501781
(1 row)