問題重現(xiàn)：
1、PG客戶端:
postgres=# create table text_test (id int,info text);CREATE TABLEpostgres=# insert into text_test values (1,E'/0x00');ERROR: invalid byte sequence for encoding "UTF8": 0x00
2、SQL Server產(chǎn)生數(shù)據(jù)
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' + '');
然后通過java程序進(jìn)行獲取數(shù)據(jù)并插入到PG，同樣會(huì)得到錯(cuò)誤信息：
invalid byte sequence for encoding "UTF8": 0x00
首先我們認(rèn)為此為gb2312轉(zhuǎn)化到UTF8時(shí)，發(fā)生了無法轉(zhuǎn)化的錯(cuò)誤。經(jīng)查UTF8是變長的, 1-6個(gè)字節(jié)。他的編碼規(guī)則如下：
| Bits | Last code point | Byte 1 | Byte 2 | Byte 3 | Byte 4 | Byte 5 | Byte 6 |
| 7 | U+007F | 0xxxxxxx | |||||
| 11 | U+07FF | 110xxxxx | 10xxxxxx | ||||
| 16 | U+FFFF | 1110xxxx | 10xxxxxx | 10xxxxxx | |||
| 21 | U+1FFFFF | 11110xxx | 10xxxxxx | 10xxxxxx | 10xxxxxx | ||
| 26 | U+3FFFFFF | 111110xx | 10xxxxxx | 10xxxxxx | 10xxxxxx | 10xxxxxx | |
| 31 | U+7FFFFFFF | 1111110x | 10xxxxxx | 10xxxxxx | 10xxxxxx | 10xxxxxx | 10xxxxxx |
而0x00是符合UTF8規(guī)則的。這就使我們非常詫異。然后我們發(fā)現(xiàn)有兩點(diǎn)繼而確認(rèn)了問題：
1、
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?), but it's likely going to be easier to do that in preprocessing before you load it.Source:http://stackoverflow.com/questions/1347646/postgres-error-on-insert-error-invalid-byte-sequence-for-encoding-utf8-0x0
2、
| 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
由此我們確定，是pg對(duì)null的處理和SQL Server處理是不相同的，所以在這里出現(xiàn)了錯(cuò)誤。
而導(dǎo)致這一問題的PG具體代碼如下（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函數(shù)是將錯(cuò)誤信息返回，也就是
invalid byte sequence for encoding "UTF8": 0x00
而真正導(dǎo)致這一問題的就是：
!IS_HIGHBIT_SET(*mbstr)當(dāng)*mbstr為0x00時(shí)進(jìn)入判斷，然后進(jìn)而判斷*mbstr是否為/0,當(dāng)為/0時(shí)，直接進(jìn)入函數(shù)report_invalid_encoding報(bào)錯(cuò)。
所以出現(xiàn)此問題的原因是PG和SQL Server對(duì)null的處理是不相同的。
處理方案 ：
1、將SQL Server源數(shù)據(jù)進(jìn)行修改方法，
UPDATE: This seems to work: Select * from TABLEwhere UNICODE(SUBSTRING(naughtyField, LEN(naughtyField), 1)) = 0So: Update TABLESET naughtyField = SUBSTRING(naughtyField, 1, LEN(naughtyField) - 1)where UNICODE(SUBSTRING(naughtyField, LEN(naughtyField), 1)) = 0Source:http://stackoverflow.com/questions/3533320/sql-server-remove-end-string-character-0-from-data
2、對(duì)應(yīng)用進(jìn)行修改，獲取到SQL Server數(shù)據(jù)時(shí)，將數(shù)據(jù)進(jìn)行轉(zhuǎn)化，和第一種方法異曲同工。
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