SQL Server数据迁移至PostgreSQL出错的解释以及解决方案

postgres=# create table text_test (id int,info text);
CREATE TABLE
postgres=# insert into text_test values (1,E'\0x00');
ERROR: invalid byte sequence for encoding "UTF8": 0x00

create table test_varchar(id int,name varchar(20));
insert into test_varchar values (1, 'name' + char(0));
insert into test_varchar values (1, 'name' + '');

invalid byte sequence for encoding "UTF8": 0x00

PostgreSQL doesn't support storing NULL (\0x00) characters in text fields (this is obviously different from the database NULL value, which is fully supported).

If you need to store the NULL character, you must use a bytea field - which should store anything you want, but won't support text operations on it.

Given that PostgreSQL doesn't support it in text values, there's no good way to get it to remove it. You could import your data into bytea and later convert it to text using a special function (in perl or something, maybe"border-bottom: #bbbbbb 1px solid; border-left: #bbbbbb 1px solid; padding-bottom: 0px; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Segoe UI', 'Lucida Grande', Verdana, Arial, Helvetica, sans-serif; color: #000000; font-size: 13px; border-top: #bbbbbb 1px solid; border-right: #bbbbbb 1px solid; padding-top: 0px">
  
    
      
      
Terminating character
      
      
      
Indicated by
      
    
    
      
      
Tab
      
      
      
\t
      
This is the default field terminator.
      
    
    
      
      
Newline character
      
      
      
\n
      
This is the default row terminator.
      
    
    
      
      
Carriage return/line feed
      
      
      
\r
      
    
    
      
      
Backslash1
      
      
      
\\
      
    
    
      
      
Null terminator (nonvisible terminator)2
      
      
      
\0
      
    
    
      
      
Any printable character (control characters are not printable, except null, tab, newline, and carriage return)
      
      
      
(*, A, t, l, and so on)
      
    
    
      
      
String of up to 10 printable characters, including some or all of the terminators listed earlier
      
      
      
(**\t**, end, !!!!!!!!!!, \t—\n, and so on)
      
    
  


Source:http://msdn.microsoft.com/en-us/library/ms191485.aspx
由此我们确定，是pg对null的处理和SQL Server处理是不相同的，所以在这里出现了错误。
而导致这一问题的PG具体代码如下（src/backend/utils/mb/wchar.c的pg_verify_mbstr_len）：


if (!IS_HIGHBIT_SET(*mbstr))
    {
      if (*mbstr != '\0')
      {
        mb_len++;
        mbstr++;
        len--;
        continue;
      }
      if (noError)
        return -1;
      report_invalid_encoding(encoding, mbstr, len);
    }






#define IS_HIGHBIT_SET(ch)   ((unsigned char)(ch) & HIGHBIT)
#define HIGHBIT         (0x80)




report_invalid_encoding函数是将错误信息返回，也就是
invalid byte sequence for encoding "UTF8": 0x00

而真正导致这一问题的就是：

!IS_HIGHBIT_SET(*mbstr)当*mbstr为0x00时进入判断，然后进而判断*mbstr是否为\0,当为\0时，直接进入函数report_invalid_encoding报错。
所以出现此问题的原因是PG和SQL Server对null的处理是不相同的。
处理方案 ：
1、将SQL Server源数据进行修改方法，


UPDATE: This seems to work:
 
Select * from TABLE
where UNICODE(SUBSTRING(naughtyField, LEN(naughtyField), 1)) = 0
So:
 
Update TABLE
SET naughtyField = SUBSTRING(naughtyField, 1, LEN(naughtyField) - 1)
where UNICODE(SUBSTRING(naughtyField, LEN(naughtyField), 1)) = 0
Source:http://stackoverflow.com/questions/3533320/sql-server-remove-end-string-character-0-from-data




2、对应用进行修改，获取到SQL Server数据时，将数据进行转化，和第一种方法异曲同工。