| Bug #69117 | Wasted work in method myisamchk | ||
|---|---|---|---|
| Submitted: | 2 May 2013 2:07 | Modified: | 1 Jul 2013 16:38 |
| Reporter: | Po-Chun Chang (OCA) | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: Command-line Clients | Severity: | S5 (Performance) |
| Version: | 5.6, 5.7 | OS: | Any |
| Assigned to: | CPU Architecture: | Any | |
| Tags: | patch, performance | ||
[2 May 2013 2:07]
Po-Chun Chang
Suggested patch
Attachment: patch.diff (text/plain), 602 bytes.
[26 Jun 2013 3:00]
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), 602 bytes.
[27 Jun 2013 13:40]
Ståle Deraas
Thank you for your contribution. We will include it in a coming release.
[1 Jul 2013 16:38]
Paul DuBois
Noted in 5.7.2 changelog. Several inefficiencies were corrected: A loop in Item_in_subselect::single_value_transformer() could execute too many times. The myisamchk(), my_test_if_sort_rep(), and recreate_table() functions in MyISAM code could execute too many times. Thanks to Po-Chun Chang for the patches to correct these issues.
Description: The problem appears in version 5.6 and in the latest revision 5216 in version 5.7. I attached a one-line patch that fixes it. In method "myisamchk" in myisamchk.c, the loop on "share->keyinfo" (line 1032) should break immediately after "update_index" is set to 0. All the iterations after "update_index" is set to 0 do not perform any useful work, at best they just set "update_index" again to 0. How to repeat: As long as myisamchk() is executed. Suggested fix: === modified file 'storage/myisam/myisamchk.c' --- storage/myisam/myisamchk.c 2013-02-26 06:21:48 +0000 +++ storage/myisam/myisamchk.c 2013-05-01 22:55:40 +0000 @@ -1029,8 +1029,10 @@ */ my_bool update_index=1; for (key=0 ; key < share->base.keys; key++) - if (share->keyinfo[key].flag & (HA_BINARY_PACK_KEY|HA_FULLTEXT)) + if (share->keyinfo[key].flag & (HA_BINARY_PACK_KEY|HA_FULLTEXT)) { update_index=0; + break; + } error=mi_sort_records(param,info,filename,param->opt_sort_key, /* what is the following parameter for ? */