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Displaying posts with tag: optimizer_switch (reset)

Back on disk temporary tables
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We already blog a lot on temporary tables on disk, how this could be bad for your workload and should be avoid.  Each temporary table will open a file descriptor,  external kernel call and by nature a well know file system slow operation.

We can point this benchmark simulating a working mail server


Monitoring of such queries can be trace via the status of

created_tmp_disk_tables 
Evidence of what is happening watching many Aria or MyISAM tables created on disk :

/usr/sbin/lsof …









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