前言

最近开始啃openGauss的兼容package了,先拿简单点的练练手。

UTL_URL这个包只有两个函数,“ESCAPE"和"UNESCAPE”,其实就是在其他开发语言中使用的URLENCODE和URLDECODE两个函数,主要用于对url字符串的一些特定字符进行处理,以便将url字符串作为数据传输时不引起歧义,还算是经常会用到的功能,目前已经有三方扩展支持这两个函数(https://github.com/okbob/url_encode),但是在openGauss里编译扩展有点不方便,我直接用plsql写一个,更容易安装及使用。

先尝试在oracle里还原这个包里两个函数的逻辑

ESCAPE

UTL_URL.ESCAPE (
   url                   IN VARCHAR2 CHARACTER SET ANY_CS,
   escape_reserved_chars IN BOOLEAN  DEFAULT  FALSE,
   url_charset           IN VARCHAR2 DEFAULT  utl_http.body_charset)
RETURN VARCHAR2;

ESCAPE有3个参数,分别是url字符串、是否替换保留字符(默认不替换)、url字符集
用法举例

--只传URL,另外两个参数默认
select utl_url.escape('https://www.darkathena.top/archives/我开博了') from dual;
--https://www.darkathena.top/archives/%BF%BF%BF%BF
--很明显,这里由于字符集未指定,导致转换出来的结果有误

--对于非ASCII字符以UTF8编码
select utl_url.escape('https://www.darkathena.top/archives/我开博了',url_charset=>'AL32UTF8') from dual;
--https://www.darkathena.top/archives/%E6%88%91%E5%BC%80%E5%8D%9A%E4%BA%86

--对于非ASCII字符以GBK进行编码
select utl_url.escape('https://www.darkathena.top/archives/我开博了',url_charset=>'ZHS16GBK') from dual;
--https://www.darkathena.top/archives/%CE%D2%BF%AA%B2%A9%C1%CB

--对于非ASCII字符以GBK进行编码,并替换所有保留字符
BEGIN
DBMS_OUTPUT.put_line( 
utl_url.escape('https://www.darkathena.top/archives/我开博了',TRUE,'ZHS16GBK') );
END;
/
--https%3A%2F%2Fwww.darkathena.top%2Farchives%2F%CE%D2%BF%AA%B2%A9%C1%CB

看上去不是很麻烦,只需要逐个字符进行判断,识别到需要进行转换的字符时,获取它的二进制数据,以十六进制字符串表示,并对这个十六进制字符串格式化成"%FF*n"的形式。
代码如下

CREATE OR REPLACE FUNCTION URLENCODE(url                   IN VARCHAR2 CHARACTER SET ANY_CS,
                                     escape_reserved_chars IN BOOLEAN DEFAULT FALSE,
                                     url_charset           IN VARCHAR2 DEFAULT 'al32utf8')
  RETURN VARCHAR2 AS
  L_TMP            VARCHAR2(6000);
  L_BAD            VARCHAR2(100) DEFAULT ' >%}\~];?@&<#{|^[`/:=$+''"';
  l_reserved_chars VARCHAR2(100) DEFAULT ';/?:@&=+$[]';
  L_CHAR           CHAR(1 CHAR);

BEGIN
  IF (url IS NULL) THEN
    RETURN NULL;
  END IF;
  if not escape_reserved_chars then
    L_BAD := translate(L_BAD, l_reserved_chars, '');
  end if;
  FOR I IN 1 .. LENGTH(url) LOOP
    L_CHAR := SUBSTR(url, I, 1);
    IF (INSTR(L_BAD, L_CHAR) > 0 or ascii(L_CHAR) > 255) THEN
      L_TMP := L_TMP || regexp_replace(rawtohex(utl_raw.cast_to_raw(convert(L_CHAR,
                                                                            url_charset))),
                                       '(.{2})',
                                       '%\1');
    ELSE
      L_TMP := L_TMP || L_CHAR;
    END IF;
  END LOOP;
  RETURN L_TMP;
END URLENCODE;
/

对于上面的用法举例,使用刚刚创建的URLENCODE这个函数对utl_url.escape进行替换,均可执行,且输出结果正确

UNESCAPE

UTL_URL.UNESCAPE (
   url            IN VARCHAR2 CHARACTER SET ANY_CS,
   url_charset    IN VARCHAR2 DEFAULT utl_http.body_charset)
RETURN VARCHAR2;

UNESCAPE有两个参数,分别是已经被urldecode的url字符串,和url字符集
用法举例

--以GBK字符集对URL进行还原
select utl_url.unescape('https://www.darkathena.top/archives/%CE%D2%BF%AA%B2%A9%C1%CB','ZHS16GBK') from dual;
--https://www.darkathena.top/archives/我开博了

--以UTF8字符集对URL进行还原
select utl_url.unescape('https://www.darkathena.top/archives/%E6%88%91%E5%BC%80%E5%8D%9A%E4%BA%86','AL32UTF8') from dual;
--https://www.darkathena.top/archives/我开博了

这个看上去比上面那个要难处理一点,因为我考虑到不同字符集的字节个数是不一样的,但是后来一想,可以先不用考虑字符集,普通字符转成二进制数据,十六进制字符去掉百分号直接作为十六进制形式的二进制数据,把所有的二进制数据拼起来,最后再根据指定的字符集转换成可显示字符串即可
代码如下

CREATE OR REPLACE FUNCTION URLDECODE(url         IN VARCHAR2 CHARACTER SET ANY_CS,
                                     url_charset IN VARCHAR2 DEFAULT 'AL32UTF8')
  RETURN VARCHAR2 IS
  L_RETURN VARCHAR2(2000);
BEGIN
  select CONVERT(UTL_RAW.cast_to_varchar2(LISTAGG(CASE
                                                    WHEN LENGTH(A) = 3 THEN
                                                     HEXTORAW(REPLACE(A, '%'))
                                                    ELSE
                                                     UTL_RAW.cast_to_raw(A)
                                                  END) --within group (order by 1) --18c以下取消本行注释
                                                  ),
                 url_charset)
    INTO L_RETURN
    from (select REGEXP_SUBSTR(url, '(%.{2}|.)', 1, LEVEL) A
            from DUAL
          CONNECT BY LENGTH(REGEXP_SUBSTR(url, '(%.{2}|.)', 1, LEVEL)) > 0) A;
  RETURN L_RETURN;
END;
/

同样,新建的这个函数URLDECODE可以完全替代utl_url.unescape使用

到此,逻辑已经梳理完毕,接下来就是移植到openGauss了

openGauss(postgresql)兼容代码

openGauss的语法及函数和oracle还是有不少差异的,但是既然逻辑已经写出来了,改改也不是什么麻烦事,只是要注意,编码时尽量使用内置函数以提升效率

https://gitee.com/darkathena/opengauss-oracle/blob/main/oracle-package/utl_url.sql

create schema UTL_URL;

CREATE OR REPLACE FUNCTION UTL_URL.escape(url IN TEXT, escape_reserved_chars IN BOOL DEFAULT FALSE, url_charset IN TEXT DEFAULT 'UTF8')
RETURNS TEXT
LANGUAGE plpgsql
IMMUTABLE NOT FENCED NOT SHIPPABLE
AS $$
declare
  L_TMP            TEXT DEFAULT '';
  L_BAD            TEXT DEFAULT ' >%}\~];?@&<#{|^[`/:=$+''"';
  l_reserved_chars TEXT DEFAULT ';/?:@&=+$[]';
  L_CHAR           TEXT;
BEGIN
  IF (url IS NULL) THEN
    RETURN NULL;
  END IF;

  if not escape_reserved_chars then
    L_BAD := translate(L_BAD, l_reserved_chars, '');
  end if;

  FOR I IN 1..LENGTH(url) LOOP
    L_CHAR := SUBSTR(url, I, 1);
    IF (INSTR(L_BAD, L_CHAR) > 0 or ascii(L_CHAR) > 255) THEN
      L_TMP := L_TMP || regexp_replace(upper(REPLACE(convert_TO(L_CHAR, url_charset)::TEXT,'\x','')),'(.{2})',
                                       '%\1','g');
    ELSE
      L_TMP := L_TMP || L_CHAR;
    END IF;
  END LOOP;
  RETURN L_TMP;
END; $$;
/
 
CREATE OR REPLACE FUNCTION UTL_URL.unescape(url IN TEXT, url_charset IN TEXT DEFAULT 'UTF8')
RETURNS TEXT
LANGUAGE sql
IMMUTABLE NOT FENCED NOT SHIPPABLE
AS $$
  select CONVERT_FROM(string_agg(CASE
                                   WHEN LENGTH(A) = 3 THEN
                                     decode(REPLACE(A, '%'), 'HEX')
                                   ELSE
                                     A :: bytea
                                 END, '' :: bytea), url_charset) 
    from (select a
            from (select (regexp_matches(url, '(%..|.)', 'g')) [ 1 ] a ) ) A;
$$;
/

测试

select utl_url.escape('https://www.darkathena.top/archives/我开博了',TRUE,url_charset=>'GBK') union all
select utl_url.escape('https://www.darkathena.top/archives/我开博了',url_charset=>'GBK')  union all
select utl_url.escape('https://www.darkathena.top/archives/我开博了',url_charset=>'UTF8')  union all
select utl_url.unescape('https://www.darkathena.top/archives/%CE%D2%BF%AA%B2%A9%C1%CB','GBK')  union all
select utl_url.unescape('https://www.darkathena.top/archives/%E6%88%91%E5%BC%80%E5%8D%9A%E4%BA%86','UTF8') ;

另外,如果是openGauss2.1.0以上版本,且安装数据库时选择了A兼容模式,那么也可以使用package的方式,不需要新建schema

CREATE OR REPLACE package pg_catalog.UTL_URL
as
  function escape(url IN TEXT, escape_reserved_chars IN BOOL DEFAULT FALSE, url_charset IN TEXT DEFAULT 'UTF8')
  RETURN TEXT;

  FUNCTION unescape(url IN TEXT, url_charset IN TEXT DEFAULT 'UTF8')
  RETURN TEXT;
end UTL_URL;
/

CREATE OR REPLACE package body pg_catalog.UTL_URL
as
  function escape(url IN TEXT, escape_reserved_chars IN BOOL DEFAULT FALSE, url_charset IN TEXT DEFAULT 'UTF8')
  RETURN TEXT
  IMMUTABLE NOT FENCED NOT SHIPPABLE
  AS
    L_TMP            TEXT DEFAULT '';
    L_BAD            TEXT DEFAULT ' >%}\~];?@&<#{|^[`/:=$+''"';
    l_reserved_chars TEXT DEFAULT ';/?:@&=+$[]';
    L_CHAR           TEXT;
  BEGIN
    IF (url IS NULL) THEN
      RETURN NULL;
    END IF;

    if not escape_reserved_chars then
      L_BAD := translate(L_BAD, l_reserved_chars, '');
    end if;

    FOR I IN 1.. LENGTH(url) LOOP
      L_CHAR := SUBSTR(url, I, 1);
      IF (INSTR(L_BAD, L_CHAR) > 0 or ascii(L_CHAR) > 255) THEN
        L_TMP := L_TMP || regexp_replace(upper(REPLACE(convert_TO(L_CHAR, url_charset)::TEXT,'\x','')),'(.{2})',
                                       '%\1','g');
      ELSE
        L_TMP := L_TMP || L_CHAR;
      END IF;
    END LOOP;
    RETURN L_TMP;
  END;

  FUNCTION unescape(url IN TEXT, url_charset IN TEXT DEFAULT 'UTF8')
  RETURN TEXT
  IMMUTABLE NOT FENCED NOT SHIPPABLE
  AS
    l_return text;
  begin
    select CONVERT_FROM(string_agg(CASE
                                     WHEN LENGTH(A) = 3 THEN
                                       decode(REPLACE(A, '%'), 'HEX')
                                     ELSE
                                       A :: bytea
                                   END, '' :: bytea), url_charset) into l_return
      from (select a
              from (select (regexp_matches(url, '(%..|.)', 'g')) [ 1 ] a ) ) A;
    return l_return;
  end;
end UTL_URL;
/

• 本文作者： DarkAthena
• 本文链接： https://www.darkathena.top/archives/opengauss-utl-url-pkg
• 版权声明： 本博客所有文章除特别声明外，均采用CC BY-NC-SA 3.0 许可协议。转载请注明出处！