Question

我正在尝试转换非常大数字的十六进制字符串到NUMERIC列

CREATE OR REPLACE FUNCTION hex_to_int(hexval varchar) RETURNS NUMERIC AS $$
DECLARE
   result  NUMERIC;
BEGIN
 EXECUTE 'SELECT x''' || hexval || '''::NUMERIC(40,0)' INTO result;
 RETURN result;
END;
$$
LANGUAGE 'plpgsql' IMMUTABLE STRICT;

我正试图这样做：

select hex_to_int(tx.value) from internal_transaction tx

我得到的错误是：

[42846] ERROR: cannot cast type bit to numeric Where: PL/pgSQL function hex_to_int(character varying) line 5 at EXECUTE statement

Answer 1

这是一种蛮力，根本不是防弹的：

CREATE OR REPLACE FUNCTION hex_to_int(hexval varchar) RETURNS numeric AS $$
DECLARE
  result  NUMERIC;
  i integer;
  len integer;
  hexchar varchar;
BEGIN

  result := 0;
  len := length(hexval);

  for i in 1..len loop
    hexchar := substr(hexval, len - i + 1, 1);
    result := result + round(16 ^ (i - 1)::dec * case
      when hexchar between '0' and '9' then cast (hexchar as int)
      when upper (hexchar) between 'A' and 'F' then ascii(upper(hexchar)) - 55
    end);
  end loop;

 RETURN result;
END;
$$
LANGUAGE 'plpgsql' IMMUTABLE STRICT;

select hex_to_int('12AE34F');  -- returns 19587919

或者，如果你安装了PL / Perl，你可以让它做重物：

CREATE OR REPLACE FUNCTION hex_to_int_perl(varchar)
  RETURNS numeric AS
$BODY$
  my ($hex) = @_;
  return sprintf "%d", hex($hex);
$BODY$
  LANGUAGE plperl VOLATILE
  COST 100;

select hex_to_int_perl('12AE34F');  -- returns 19587919

我不认为非Perl可以使用负数，而且我很确定如果你输入一个非十六进制值，两者都会给你带来不好的结果，但那些很容易陷入陷阱和处理，取决于你想要的功能。

Answer 2

我的用例是将十六进制SHA-1哈希值转换为整数。在整个功能中没有注意数字精度，这个用例很容易发现缺点;但是，具有更大“非常大数量”的用例肯定很容易识别。

考虑到一些SHA-1哈希值，第一个接受的答案的解决方案产生了以下结果：

SELECT hex_to_int('356e90d2a2d414ba8757ec2ab91f2f19c481d4c3');
-- returns 305042208670409000000000000000000000000000000000

SELECT hex_to_int('aaa9f7193cc8efe7e98145b0f8d9ae5f1712c25b');
-- returns 974318782301086000000000000000000000000000000000

当然，每个结果都用这么多零填充右边是用例精度不足的标志。

这是我最终获得所需精度的地方：

CREATE OR REPLACE FUNCTION hex_to_int(hexVal varchar) RETURNS numeric(1000) AS $$
DECLARE
    intVal numeric(1000) := 0;
    hexLength integer;
    i integer;
    hexDigit varchar;
BEGIN
    hexLength := length(hexVal);

    FOR i IN 1..hexLength
    LOOP
        hexDigit := substr(hexVal, hexLength - i + 1, 1);
        intVal :=
            intVal +
            CASE
                WHEN hexDigit BETWEEN '0' AND '9' THEN CAST(hexDigit AS numeric(1000))
                WHEN upper(hexDigit) BETWEEN 'A' AND 'F' THEN CAST(ascii(upper(hexDigit)) - 55 AS numeric(1000))
            END *
            CAST(16 AS numeric(1000)) ^ CAST(i - 1 AS numeric(1000));
    END LOOP;

    RETURN intVal;
END;
$$
LANGUAGE 'plpgsql' IMMUTABLE STRICT;


SELECT hex_to_int('356e90d2a2d414ba8757ec2ab91f2f19c481d4c3');
-- returns 305042208670409212880202819376501392142011323587

SELECT hex_to_int('aaa9f7193cc8efe7e98145b0f8d9ae5f1712c25b');
-- returns 974318782301085717223606317572453925850501530203

Answer 3

还有另一个转换功能。这样做的目的是减少循环中的步骤数，从而减少算术运算的次数。

create or replace function hex_to_numeric(str text)
returns numeric language plpgsql immutable strict as $$
declare
    i int;
    n int = length(str)/ 8;
    res dec = 0;
begin
    str := lpad($1, (n+ 1)* 8, '0');
    for i in 0..n loop
        if i > 0 then 
            res:= res * 4294967296; 
        end if;
        res:= res + concat('x', substr(str, i* 8+ 1, 8))::bit(32)::bigint::dec;
    end loop;
    return res;
end $$;

一些测试：

select hex, hex_to_numeric(hex) 
from   (
   values ('ff'::text),
        ('7fffffff'),
        ('80000000'),
        ('deadbeef'),
        ('7fffffffffffffff'),
        ('8000000000000000'),
        ('ffffffffffffffff'),
        ('ffffffffffffffff123'),
        ('4540a085e7334d6494dd6a7378c579f6')
   ) t(hex);

               hex                |             hex_to_numeric             
----------------------------------+----------------------------------------
 ff                               |                                    255
 7fffffff                         |                             2147483647
 80000000                         |                             2147483648
 deadbeef                         |                             3735928559
 7fffffffffffffff                 |                    9223372036854775807
 8000000000000000                 |                    9223372036854775808
 ffffffffffffffff                 |                   18446744073709551615
 ffffffffffffffff123              |                75557863725914323415331
 4540a085e7334d6494dd6a7378c579f6 | 92052294502540680826164862654582454774
(9 rows)

PostgreSQL：将非常大数字的十六进制字符串转换为NUMERIC

3 个答案: