| Bug #18875 | Default value of tmp_table_size is meaningless | ||
|---|---|---|---|
| Submitted: | 7 Apr 2006 5:00 | Modified: | 26 Sep 2006 19:52 |
| Reporter: | Jeremy Cole (Basic Quality Contributor) (OCA) | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server | Severity: | S3 (Non-critical) |
| Version: | 4.1/5.0/5.1 | OS: | n/a |
| Assigned to: | Chad MILLER | CPU Architecture: | Any |
[7 Apr 2006 5:27]
Jeremy Cole
Further, it would make sense to emit a warning (to the error file) when setting tmp_table_size higher than max_heap_table_size, and clip the value of tmp_table_size to that of max_heap_table_size. When setting it via the SET command it makes sense to do the same and emit the warning for SHOW WARNINGS instead.
[7 Apr 2006 18:30]
MySQL Verification Team
Thank you for the bug report.
[11 Aug 2006 13:25]
Chad MILLER
I'm wary of changing the default value of either for stable releases. This bug isn't causing faults, and if anyone is explicitly setting one of the variables then a change in default for the /other/ variable might cause failures. For stable releases, this is a documentation problem. I will lower the default tmp_table_size in a development version, 5.1 . Documenters: Please make it explicit that where tmp_table_size is used, it is maximally bounded by max_heap_table_size .
[11 Aug 2006 13:48]
Bugs System
A patch for this bug has been committed. After review, it may be pushed to the relevant source trees for release in the next version. You can access the patch from: http://lists.mysql.com/commits/10312 ChangeSet@1.2272, 2006-08-11 09:49:01-04:00, cmiller@zippy.cornsilk.net +1 -0 Bug#18875: Default value of tmp_table_size is meaningless It makes no sense to have a default tmp_table_size larger than the max_heap_table_size . In usage, the tmp is ever limited to the max value, so I lowered the default tmp to the default max value. A great idea would be to emit a warning when the tmp_table_size is set to greater than max_heap_table_size .
[12 Aug 2006 12:11]
Chad MILLER
This is in the Maint team-tree and should be available in 5.1.12-beta .
[13 Sep 2006 8:05]
Timothy Smith
Merged up to 5.1.12
[26 Sep 2006 19:52]
Paul DuBois
Noted in 5.1.12 changelog.
Description: The default value of tmp_table_size (32M) is meaningless, as it is less than max_heap_table_size (16M), which then becomes the real maximum for an in-memory temporary table. How to repeat: mysql> select @@global.tmp_table_size, @@global.max_heap_table_size \G *************************** 1. row *************************** @@global.tmp_table_size: 33554432 @@global.max_heap_table_size: 16777216 Suggested fix: Decrease the default of tmp_table_size to 16M, or increase the default of max_heap_table_size to 32M.