| Bug #60227 | Much overhead for MD5() and SHA1() on short strings | ||
|---|---|---|---|
| Submitted: | 23 Feb 2011 21:56 | Modified: | 11 Jun 2012 16:37 |
| Reporter: | Linhai Song | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: DDL | Severity: | S5 (Performance) |
| Version: | 5.1.54, 5.5.26 | OS: | Any |
| Assigned to: | CPU Architecture: | Any | |
| Tags: | Contribution, md5, performance, sha1 | ||
[12 Mar 2011 20:06]
Linhai Song
What does tag "contribution" mean? I have done some unit tests, and results show that the patch will work better than calling sprintf. But code fragment I report is only executed once when executing "ALTER VIEW" command. I think using patch may make the performance only a little better.
[26 May 2012 10:38]
Valeriy Kravchuk
Still same suboptimal code is used in 5.5.26. Time to fix this.
[11 Jun 2012 16:37]
Paul DuBois
Noted in 5.6.6 changelog. The MD5() and SHA1() functions had excessive overhead for short strings.
Description: After reading report of mysqlbug49491, I find a place which is exact the same situation as mysqlbug49491, but it is not reported in the original bug report, and it is not fixed in the latest mysql-5.1.54 version. The place I find is: mysql-5.1.54/sql/table.cc:3020 void TABLE_LIST::calc_md5(char *buffer) { uchar digest[16]; MY_MD5_HASH(digest, (uchar *) select_stmt.str, select_stmt.length); sprintf((char *) buffer, "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x", digest[0], digest[1], digest[2], digest[3], digest[4], digest[5], digest[6], digest[7], digest[8], digest[9], digest[10], digest[11], digest[12], digest[13], digest[14], digest[15]); } I think this place should also be patched the same way as mysqlbug49491 BTW. mysqlbug49491 is not fixed in latest mysql-5.0.91 version. The place I find is also in the latest mysql-5.0.91 version and latest mysql-5.5.8 version. How to repeat: code review Suggested fix: I put the patch for mysqlbug49491 here: static void array_to_hex(char *to, const unsigned char *str, uint len) { const unsigned char *str_end= str + len; for (; str != str_end; ++str) { *to++= _dig_vec_lower[((uchar) *str) >> 4]; *to++= _dig_vec_lower[((uchar) *str) & 0x0F]; } }