| Bug #10184 | auto-increment key not checked for value if in composite key | ||
|---|---|---|---|
| Submitted: | 26 Apr 2005 16:32 | Modified: | 13 May 2005 12:29 |
| Reporter: | Sinisa Milivojevic | Email Updates: | |
| Status: | Not a Bug | Impact on me: | |
| Category: | MySQL Server: MyISAM storage engine | Severity: | S3 (Non-critical) |
| Version: | 4.0 and higher | OS: | Any (any) |
| Assigned to: | Michael Widenius | CPU Architecture: | Any |
[13 May 2005 12:29]
Michael Widenius
Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.mysql.com/documentation/ and the instructions on how to report a bug at http://bugs.mysql.com/how-to-report.php Additional info: This is correct behaviour as the auto-increment part is not the first part of the key. In this case the value for the auto-increment key is calculated on insert based on the existing values in the table.
Description: If auto-incremented column is present in they segmented key, but not as a first part of it, then after each INSERT / UPDATE no checks are made for the integrity of the value. No checks are made against the highest auto-inc value in the table. A cause of it is that share->base.auto_key is 0 , instead of 1 !!! Then in mi_check.c , this branch is skipped: if ((uint) share->base.auto_key -1 == key) and this branch has this important check: if (info->s->state.auto_increment > save_auto_value) This bug is MyISAM specific. How to repeat: DROP TABLE IF EXISTS t1; CREATE TABLE t1 ( a INT AUTO_INCREMENT, b BLOB, PRIMARY KEY (b(10),a)); INSERT INTO t1 (b) VALUES ('aaaa'); CHECK TABLE t1; INSERT INTO t1 (b) VALUES (''); CHECK TABLE t1; INSERT INTO t1 (b) VALUES ('bbbb'); CHECK TABLE t1; DROP TABLE IF EXISTS t1;