Bug #5514 tmp_table_size limited by max_heap_table_size / maybe insufficent documentation
Submitted: 10 Sep 2004 10:13 Modified: 10 Sep 2004 12:25
Reporter: Martin Friebe (Gold Quality Contributor) (OCA) Email Updates:
Status: Duplicate Impact on me:
Category:MySQL Server Severity:S3 (Non-critical)
Version:4.0.18 OS:
Assigned to: Assigned Account CPU Architecture:Any

[10 Sep 2004 10:13] Martin Friebe
Not sure, if this is considerable a bug, if not maybe it should be explicitly mentioned in the docomentation?

temporary table (For large / complex queries) are heap (in memory) tables, so it is not necessarely wrong for them to be limited by both:
tmp_table_size and heap_table_size.

On the other hand that limits the flexibility of tmp_table_size, which you might want to set to a higher value than hap_table_size.

How to repeat:
create large enough tables and perform a querry that uses a tmp_table in memory
set your tmp_table_size high enough.

now set your heap_table_size lower than the amount of memory used, by the above query, rerun the query. Mysql will create a temp table on disk.
[10 Sep 2004 12:25] Sergei Golubchik
Please do not submit the same bug more than once. An existing
bug report already describes this very problem. Even if you feel
that your issue is somewhat different, the resolution is likely
to be the same. Because of this, we hope you add your comments
to the original bug instead.

Thank you for your interest in MySQL.

Additional info:

see http://bugs.mysql.com/4291