PostgreSQL表大吗？内存不足？

我有一个约380万行的表.当我查询整个表格时,我得到了

ERROR: value overflows numeric format

引用用户定义函数返回的值.
但是,如果我将表格大致分成两半(见下文),一切正常.

SELECT day,item,price,CAST(my_func(price) OVER (PARTITION BY item ORDER BY day) AS numeric(8,2)),FROM my_table
    --WHERE day < '3/1/2013';
    --WHERE day >= '3/1/2013';

具有WHERE子句的语句在没有错误的情况下执行.

价格是数字(8,2),价格列中没有任何数字大于数字(8,2).无论如何,将格式更改为数字(20,2)没有任何区别.

这是表定义：

CREATE TABLE my_table
    (
        item    character(5)    NOT NULL,day     date            NOT NULL,price   numeric(8,CONSTRAINT  my_table_pk PRIMARY KEY (item,day)
    );

……和功能：

CREATE OR REPLACE FUNCTION my_func2 (avg numeric,IN price numeric)
    RETURNS numeric AS $$
    DECLARE
        alpha numeric;
    BEGIN
        alpha := 2.0/51;
        RETURN
            CASE
                WHEN avg IS NULL THEN price  -- avg is NULL for the first row,so price is returned
                ELSE round((alpha * price + (1-alpha) * avg),2)
            END;
    END;
    $$LANGUAGE PLPgsql;

…用于聚合：

CREATE AGGREGATE my_func(numeric) (SFUNC = my_func2,STYPE = numeric);

解决方法

错误发生在您的演员操作中.格式数字(8,2)非常严格,可能my_func()返回不满足格式定义的值.要演示这一点,请查看以下查询：

select 12.34::numeric(8,2);
 numeric 
---------
   12.34

select 12.345678::numeric(8,2);
 numeric 
---------
   12.35

select 12.3456789::numeric(8,2);
 numeric 
---------
   12.35

select 123456.123456789::numeric(8,2);
  numeric  
-----------
 123456.12

select 1234567.123456789::numeric(8,2);
ERROR:  numeric field overflow
DETAIL:  A field with precision 8,scale 2 must round to an absolute value less than 10^6.

select 1234567.8::numeric(8,scale 2 must round to an absolute value less than 10^6.

如果您注意到,返回的数字的总数字不得超过8位,并且总是有2位小数.最后两个查询会出错,因为它们应该返回超过8位数.例如,您希望将数字1234567.123456789舍入为1234567.12,但1234567.12由9位数组成,而不是8.对于数字1234567.8也是如此,即使您有8位数字也是如此.这是因为在返回的数值中你想要2个十进制数字,所以postgres sohuld输出1234567.80但是再次,这里你有9位数而不是8位数.

换句话说,您有不同的方法来解决此问题：

>使用数字(16,2)为16位总数(选择所需的数字),增加my_func()所需的整数十进制数字.
>使用其他数字格式,例如数字或实数.例如：(my_func(price)OVER(PARTITION BY item ORDER BY day)):: real
>如果您需要特定的小数长度和无限的总数位数,请尝试round(my_func(price)OVER(PARTITION BY item ORDER BY day),2).否则,编辑my_func()以返回round(returned_value,2).

为了帮助您理解和/或找到导致错误的原因,请考虑这一点.对于评估my_func()的至少一个或一行,您会在左侧获得一个数字超过6位的数字.要查找哪一行生成错误,您只需执行以下查询：

WITH not_casted AS (
    SELECT day,my_func(price) OVER (PARTITION BY item ORDER BY day) AS fprice
    FROM my_table
)
SELECT * FROM not_casted
WHERE fprice > 999999.99

此查询返回的行会生成强制转换错误.显然,如果您没有在my_func()内部对数字(8,2)进行类型转换,则此方法有效,否则将在类型转换的值上生成错误.在不知道功能代码的情况下,不可能做出其他假设.

UPDATE

我提出了一个基于模拟的例子.代码执行以下操作：
– 创建具有不同类型转换和舍入方法的不同AGGREGATE
– 对作为数据的模拟随机样本执行每个AGGREGATE(希望如此).它每天产生10个价格,每个价格在31天内有自己的项目共计10个项目.这对于证明精度损失并不重要,所以如果数据没有正确模拟,请不要怪我:)

这是创建四个函数和聚合的代码：

-- typecast price and arithmetics to numeric(8,2)
CREATE OR REPLACE FUNCTION my_func_numeric_8_2_a (avg numeric(8,IN price numeric(8,2))
RETURNS numeric(8,2) AS $$
DECLARE
    alpha numeric;
BEGIN
    alpha := 2.0/51;
    RETURN
        CASE
            WHEN avg IS NULL THEN price
            ELSE (alpha * price + (1-alpha) * avg)::numeric(8,2)
        END;
    END;
$$LANGUAGE PLPgsql;
CREATE AGGREGATE my_func_numeric_8_2(numeric(8,2)) (SFUNC = my_func_numeric_8_2_a,STYPE = numeric(8,2));


-- typecast price and arithmetics to numeric and round(arithmetics,2)
CREATE OR REPLACE FUNCTION my_func_numeric_round_a(avg numeric,IN price numeric)
RETURNS numeric AS $$
DECLARE
    alpha numeric;
BEGIN
    alpha := 2.0/51;
    RETURN
    CASE
        WHEN avg IS NULL THEN price
            ELSE round((alpha * price + (1-alpha) * avg),2)
        END;
    END;
$$LANGUAGE PLPgsql;
CREATE AGGREGATE my_func_numeric_round(numeric) (SFUNC = my_func_numeric_round_a,STYPE = numeric);

-- no typecast (double precision type)
CREATE OR REPLACE FUNCTION my_func_dp_a(avg double precision,IN price double precision)
RETURNS double precision AS $$
DECLARE
    alpha double precision;
BEGIN
    alpha := 2.0/51;
    RETURN
    CASE
        WHEN avg IS NULL THEN price
            ELSE (alpha * price + (1-alpha) * avg)
        END;
    END;
$$LANGUAGE PLPgsql;
CREATE AGGREGATE my_func_dp(double precision) (SFUNC = my_func_dp_a,STYPE = double precision);

-- typecast price and arithmetics to numeric
CREATE OR REPLACE FUNCTION my_func_numeric_a(avg numeric,IN price numeric)
RETURNS numeric AS $$
DECLARE
    alpha numeric;
BEGIN
    alpha := 2.0/51;
    RETURN
    CASE
        WHEN avg IS NULL THEN price
            ELSE (alpha * price + (1-alpha) * avg)
        END;
    END;
$$LANGUAGE PLPgsql;
CREATE AGGREGATE my_func_numeric(numeric) (SFUNC = my_func_numeric_a,STYPE = numeric);

现在,代码来模拟数据并应用这三个函数：

WITH sample AS
(
    SELECT "day",(random())*10 AS price,generate_series(1,10)::text AS item
    FROM (SELECT generate_series('2000-01-01'::timestamp,'2000-01-31'::timestamp,'1 day'::interval)::date AS "day") AS calendar
)
SELECT  "day",-- typecast price and arithmetics to numeric(8,2)
        my_func_numeric_8_2(price::numeric(8,2))  OVER (PARTITION BY item ORDER BY "day") AS numeric_8_2,-- typecast price and arithmetics to numeric and round(arithmetics,2)
        my_func_numeric_round(price::numeric)  OVER (PARTITION BY item ORDER BY "day") AS numeric_round,-- typecast price and arithmetics to numeric and round the final result
        round(my_func_numeric(price::numeric)  OVER (PARTITION BY item ORDER BY "day"),2) AS round_numeric,-- no typecast (double precision type)
        my_func_dp(price)  OVER (PARTITION BY item ORDER BY "day") AS no_typecast,-- typecast price and arithmetics to numeric
        my_func_numeric(price::numeric)  OVER (PARTITION BY item ORDER BY "day") AS numeric
FROM sample
ORDER BY item,"day"

由于random()的使用,每个查询执行都会生成不同的结果.向下滚动结果,您会看到许多行具有不同的值,即使价格与计算所有四个值相同.此外,通过降低精度损失(或提高精度)对列进行排序：my_func_dp(price)是四者之间最精确的,而my_func_numeric_8_2(price :: numeric(8,2))则不太精确,但最“精确”精确”.

如果从命令行运行上一个查询,您会注意到my_func_numeric(price :: numeric)返回长度增加的数字,因为数字尽可能精确,因此他的固定长度可能会有所不同.如果你从pgAdmin执行它,你将得到一个全长数字的四舍五入数字.

PostgreSQL表大吗？内存不足？

解决方法

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