| Bug #69377 | Wasted work in method row_check_index_for_mysql() | ||
|---|---|---|---|
| Submitted: | 1 Jun 2013 23:25 | Modified: | 4 Jul 2013 12:07 |
| Reporter: | Po-Chun Chang (OCA) | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: InnoDB storage engine | Severity: | S5 (Performance) |
| Version: | 5.6, 5.7 | OS: | Any |
| Assigned to: | CPU Architecture: | Any | |
| Tags: | patch, performance | ||
[1 Jun 2013 23:25]
Po-Chun Chang
Suggested patch
Attachment: patch.diff (text/plain), 308 bytes.
[2 Jun 2013 10:26]
MySQL Verification Team
thank you for the report. fwiw, in 5.7.2, the function is row_scan_index_for_mysql
[26 Jun 2013 2:57]
Po-Chun Chang
Suggested patch (*) I confirm the code being submitted is offered under the terms of the OCA, and that I am authorized to contribute it.
Contribution: patch.diff (text/plain), 308 bytes.
[27 Jun 2013 8:15]
Ståle Deraas
Thanks a lot. We will include you contribution.
[4 Jul 2013 12:07]
Bugs System
Added a changelog entry to 5.6.13, 5.7.2: "The "row_check_index_for_mysql" method, which checks for NULL fields during an index scan or "CHECK TABLE" operation, would iterate unnecessarily." Thank you for the bug report.
[24 Jul 2013 14:43]
Paul DuBois
Addition to changelog entry: Thanks to Po-Chun Chang for the patch to correct this issue.
Description: The problem appears in version 5.6 and in the latest revision 5216 in version 5.7. I have attached a simple one-line patch (patch.diff) that fixes it. In method "row_check_index_for_mysql()" in row0mysql.cc, the loop on line 5418 should break immediately after "contains_null" is set to "TRUE". All the iterations after "contains_null" is set to "TRUE" do not perform any useful work, at best they just set "contains_null" again to "TRUE". How to repeat: Once row_check_index_for_mysql() is executed. Suggested fix: === modified file 'storage/innobase/row/row0mysql.cc' --- storage/innobase/row/row0mysql.cc 2013-03-26 13:01:45 +0000 +++ storage/innobase/row/row0mysql.cc 2013-06-01 23:18:32 +0000 @@ -5422,6 +5422,7 @@ dtuple_get_nth_field(prev_entry, i))) { contains_null = TRUE; + break; } }