Comments on: TMP_TABLE_SIZE and MAX_HEAP_TABLE_SIZE http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/ Everything about MySQL Performance Tue, 02 Dec 2008 12:43:26 +0000 http://wordpress.org/?v=2.5.1 By: rajeesh http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-193871 rajeesh Thu, 15 Nov 2007 10:36:20 +0000 http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-193871 tmp_table_size=45M , if its increse or decrese what will the effect of mysql database tmp_table_size=45M , if its increse or decrese what will the effect of mysql database

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]]> By: peter http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-35418 peter Tue, 23 Jan 2007 20:03:23 +0000 http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-35418 Thank you James, I see it got added there. As MySQL old timer I did not get back to that page for other than new variables as I remember meaning about them. The quote I gave was from this url: http://dev.mysql.com/doc/refman/5.0/en/memory-storage-engine.html I guess I would expect working do be different in this place to. It is probably hard to keep such large document synchronized. Thank you James,

I see it got added there. As MySQL old timer I did not get back to that page for other than new variables as I remember meaning about them.

The quote I gave was from this url:

http://dev.mysql.com/doc/refman/5.0/en/memory-storage-engine.html

I guess I would expect working do be different in this place to.

It is probably hard to keep such large document synchronized.

]]> By: James Holt http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-35416 James Holt Tue, 23 Jan 2007 19:48:31 +0000 http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-35416 Peter, reading this I thought I recalled reading about it in the docs somewhere. I looked around and found it here: http://dev.mysql.com/doc/refman/5.1/en/server-system-variables.html (scroll down to tmp_table_size) Not defending the behavior by any stretch; it is highly anti-intuitive. -James Holt Peter, reading this I thought I recalled reading about it in the docs somewhere.
I looked around and found it here:

http://dev.mysql.com/doc/refman/5.1/en/server-system-variables.html
(scroll down to tmp_table_size)

Not defending the behavior by any stretch; it is highly anti-intuitive.

-James Holt

]]> By: James Day http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-34553 James Day Mon, 22 Jan 2007 06:51:47 +0000 http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-34553 Peter, thanks for mentioning this. I expect that the plan will be changed now Sergei knows that it would break backwards compatibility. A new synonym for tmp_table_size that is the memory limit and a new variable for disk size would do the job without breaking existing setups. Then tmp_table_size can be deprecated. Peter, thanks for mentioning this. I expect that the plan will be changed now Sergei knows that it would break backwards compatibility. A new synonym for tmp_table_size that is the memory limit and a new variable for disk size would do the job without breaking existing setups. Then tmp_table_size can be deprecated.

]]> By: peter http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-34308 peter Sun, 21 Jan 2007 22:44:10 +0000 http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-34308 Thank you for looking into in Sergei While fixing bug I just would make sure there are limited behavior changes compared to old timers expectations. Thank you for looking into in Sergei

While fixing bug I just would make sure there are limited behavior changes compared to old timers expectations.

]]> By: Sergei Golubchik http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-34307 Sergei Golubchik Sun, 21 Jan 2007 22:41:45 +0000 http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-34307 I saw that in the code. But now, after testing, I see that, indeed, tmp_table_size doesn't limit the size of on-disk tables (table->s->max_rows is set to limit it, but it's not copied to ci->max_rows for mi_create to see it) - it must be a bug too. I saw that in the code. But now, after testing, I see that, indeed, tmp_table_size doesn’t limit the size of on-disk tables (table->s->max_rows is set to limit it, but it’s not copied to ci->max_rows for mi_create to see it) - it must be a bug too.

]]> By: peter http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-34300 peter Sun, 21 Jan 2007 21:11:05 +0000 http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-34300 Sergei, Yes I know lower value was used but it was not documented - I quoted the manual and config files give you the same idea - want larger in memory tables increase tmp_table_size. Now regarding "Also tmp_table_size was used to limit the size of the temporary table - no matter whether it’s in memory or on disk." Where does this come from ? I constantly see temporary tables sized in gigabytes while tmp_table_size is set to 32M or similar. If that would be correct fix would be reasonable but it is not. Simply test it :) Sergei,

Yes I know lower value was used but it was not documented - I quoted the manual and config files give you the same idea - want larger in memory tables increase tmp_table_size.

Now regarding “Also tmp_table_size was used to limit the size of the temporary table - no matter whether it’s in memory or on disk.” Where does this come from ?

I constantly see temporary tables sized in gigabytes while tmp_table_size is set to 32M or similar.

If that would be correct fix would be reasonable but it is not. Simply test it :)

]]> By: Sergei Golubchik http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-34165 Sergei Golubchik Sun, 21 Jan 2007 12:18:21 +0000 http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-34165 The description is slightly wrong. The lower value from tmp_table_size and use max_heap_table_size was used to define when temporary table was converted from memory to disk. Also tmp_table_size was used to limit the size of the temporary table - no matter whether it's in memory or on disk. And max_heap_table_size was also used to limit the size of explicitly created HEAP tables. The fix is to introduce another variable memory_tmp_table_size and use it instead of the "lower value ...", to define when a temporary table is converted to MyISAM. Thus max_heap_table_size will have no effect on temporary tables, and tmp_table_size keeps its "upper boundary" meaning. The description is slightly wrong.
The lower value from tmp_table_size and use max_heap_table_size was used to define when temporary table was converted from memory to disk.
Also tmp_table_size was used to limit the size of the temporary table - no matter whether it’s in memory or on disk.
And max_heap_table_size was also used to limit the size of explicitly created HEAP tables.

The fix is to introduce another variable memory_tmp_table_size and use it instead of the “lower value …”, to define when a temporary table is converted to MyISAM. Thus max_heap_table_size will have no effect on temporary tables, and tmp_table_size keeps its “upper boundary” meaning.

]]> By: peter http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-33914 peter Sun, 21 Jan 2007 00:20:27 +0000 http://www.mysqlperformanceblog.com/2007/01/19/tmp_table_size-and-max_heap_table_size/#comment-33914 Yes quite possible. In fact I remember there were few other cases when non documented parameters are taken into consideration Yes quite possible.

In fact I remember there were few other cases when non documented parameters are taken into consideration

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