假设您想要一个简单的逐位序数位置转换（即您不担心二进制的恭维否定等）我认为这应该适用于 8.1 等效的数据库：
CREATE OR REPLACE FUNCTION hex2dec(text) RETURNS bigint AS $$
SELECT sum(CASE WHEN v >= ascii('a') THEN v - ascii('a') + 10 ELSE v - ascii('0') END * 16^ordpos)::bigint
FROM (
SELECT n-1, ascii(substring(reverse($1), n, 1))
FROM generate_series(1, length($1)) n
) AS x(ordpos, v);
$$ LANGUAGE sql IMMUTABLE;
函数形式是可选的，它只是更容易避免多次重复参数。无论如何它应该被内联。效率可能会很糟糕，但大多数可用于更智能地执行此操作的工具似乎不适用于旧版本，这至少有效：
regress=> CREATE TABLE t AS VALUES ('c13b'), ('a'), ('f');
regress=> SELECT hex2dec(column1) FROM t;
hex2dec
---------
49467
10
15
(3 rows)
如果您可以使用regexp_split_to_array 和generate_subscripts，它可能会更快。或者更慢。我没试过。另一个可能的技巧是使用数字映射数组而不是CASE，例如：
'[48:102]={0,1,2,3,4,5,6,7,8,9,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,10,11,12,13,14,15}'::integer[]
您可以使用：
CREATE OR REPLACE FUNCTION hex2dec(text) RETURNS bigint AS $$
SELECT sum(
('[48:102]={0,1,2,3,4,5,6,7,8,9,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,10,11,12,13,14,15}'::integer[])[ v ]
* 16^ordpos
)::bigint
FROM (
SELECT n-1, ascii(substring(reverse($1), n, 1))
FROM generate_series(1, length($1)) n
) AS x(ordpos, v);
$$ LANGUAGE sql IMMUTABLE;
就我个人而言，我宁愿在客户端做，而不是争论旧 PostgreSQL 分支的有限功能，尤其是你不能加载自己的明智的用户定义的 C 函数或使用 PL/Perl，等等
在真正的 PostgreSQL 中，我只使用这个：
hex2dec.c：
#include "postgres.h"
#include "fmgr.h"
#include "utils/builtins.h"
#include "errno.h"
#include "limits.h"
#include <stdlib.h>
PG_MODULE_MAGIC;
Datum from_hex(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(hex2dec);
Datum
hex2dec(PG_FUNCTION_ARGS)
{
char *endpos;
const char *hexstr = text_to_cstring(PG_GETARG_TEXT_PP(0));
long decval = strtol(hexstr, &endpos, 16);
if (endpos[0] != '\0')
{
ereport(ERROR, (ERRCODE_INVALID_PARAMETER_VALUE, errmsg("Could not decode input string %s as hex", hexstr)));
}
if (decval == LONG_MAX && errno == ERANGE)
{
ereport(ERROR, (ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE, errmsg("Input hex string %s overflows int64", hexstr)));
}
PG_RETURN_INT64(decval);
}
生成文件：
MODULES = hex2dec
DATA = hex2dec--1.0.sql
EXTENSION = hex2dec
PG_CONFIG = pg_config
PGXS := $(shell $(PG_CONFIG) --pgxs)
include $(PGXS)
hex2dec.control：
comment = 'Utility function to convert hex strings to decimal'
default_version = '1.0'
module_pathname = '$libdir/hex2dec'
relocatable = true
hex2dec--1.0.sql：
CREATE OR REPLACE FUNCTION hex2dec(hexstr text) RETURNS bigint
AS 'hex2dec','hex2dec'
LANGUAGE c IMMUTABLE STRICT;
COMMENT ON FUNCTION hex2dec(hexstr text)
IS 'Decode the hex string passed, which may optionally have a leading 0x, as a bigint. Does not attempt to consider negative hex values.';
用法：
CREATE EXTENSION hex2dec;
postgres=# SELECT hex2dec('7fffffffffffffff');
hex2dec
---------------------
9223372036854775807
(1 row)
postgres=# SELECT hex2dec('deadbeef');
hex2dec
------------
3735928559
(1 row)
postgres=# SELECT hex2dec('12345');
hex2dec
---------
74565
(1 row)
postgres=# select hex2dec(to_hex(-1));
hex2dec
------------
4294967295
(1 row)
postgres=# SELECT hex2dec('8fffffffffffffff');
ERROR: Input hex string 8fffffffffffffff overflows int64
postgres=# SELECT hex2dec('0x7abcz123');
ERROR: Could not decode input string 0x7abcz123 as hex
性能差异......值得注意。给定样本数据：
CREATE TABLE randhex AS
SELECT '0x'||to_hex( abs(random() * (10^((random()-.5)*10)) * 10000000)::bigint) AS h
FROM generate_series(1,1000000);
从使用 C 扩展名的暖缓存中从十六进制转换为十进制大约需要 1.3，这对于一百万行来说并不是很好。无需任何转换即可读取它们需要 0.95 秒。基于 SQL 的 hex2dec 方法处理相同的行需要 36 秒。坦率地说，SQL 方法的速度如此之快让我印象深刻，而 C ext 的速度如此之慢让我感到惊讶。