| Bug #69561 | Wasted work in method recreate_table() | ||
|---|---|---|---|
| Submitted: | 25 Jun 2013 2:33 | Modified: | 1 Jul 2013 16:37 |
| Reporter: | Po-Chun Chang (OCA) | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: MyISAM storage engine | Severity: | S5 (Performance) |
| Version: | 5.6, 5.7 | OS: | Any |
| Assigned to: | CPU Architecture: | Any | |
| Tags: | patch, performance | ||
[25 Jun 2013 2:36]
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), 943 bytes.
[25 Jun 2013 5:42]
MySQL Verification Team
Hello Chang, Thank you for the report and contribution. Thanks, Umesh
[27 Jun 2013 13:42]
Ståle Deraas
Thank you for your contribution. We will include it in a coming release.
[1 Jul 2013 16:37]
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 revision 5216 in version 5.7. I attached a patch that fixes it. In method "recreate_table" in mi_check.c, the loop on line 4273 should not be executed when "pack" is FALSE. When "pack" is FALSE, all the iterations do not perform any useful work. How to repeat: Once recreate_table() is executed. Suggested fix: === modified file 'storage/myisam/mi_check.c' --- storage/myisam/mi_check.c 2013-02-27 15:33:55 +0000 +++ storage/myisam/mi_check.c 2013-06-25 02:31:36 +0000 @@ -4270,13 +4270,15 @@ /* Copy the column definitions */ memcpy((uchar*) recdef,(uchar*) share.rec, (size_t) (sizeof(MI_COLUMNDEF)*(share.base.fields+1))); - for (rec=recdef,end=recdef+share.base.fields; rec != end ; rec++) + if (unpack && !(share.options & HA_OPTION_PACK_RECORD)) { - if (unpack && !(share.options & HA_OPTION_PACK_RECORD) && - rec->type != FIELD_BLOB && - rec->type != FIELD_VARCHAR && - rec->type != FIELD_CHECK) - rec->type=(int) FIELD_NORMAL; + for (rec=recdef,end=recdef+share.base.fields; rec != end ; rec++) + { + if (rec->type != FIELD_BLOB && + rec->type != FIELD_VARCHAR && + rec->type != FIELD_CHECK) + rec->type=(int) FIELD_NORMAL; + } } /* Change the new key to point at the saved key segments */