See sort_buffer_size This parameter (the connect level parameter, MySQL5.7, the default value is 1048576 bytes, that is, 1MB) The default value is so small,
Think about whether it is possible to turn up a little bit, anyway the memory is dozens of GB, also do not care about this several MB.
Note: The author attempts to modify the value of this parameter, in the typical sort (large table, the sorting field without the index of the condition) query, Sort_buffer_size modification before and after, there appears to be no significant difference in performance,
In other words, the default configuration is sufficient, or the current value of this parameter to understand the values are not enough in place.
including MySQL in other parameters, looking at small, only a few MB size, want to try to adjust a little bit, it is not so, no wonder, "high-performance MySQL," the author said: "(certain premise) can even forget some configuration files exist"
Before listening to some veteran said: Some configurable parameters, no 100% grasp, do not go to arbitrary modification, modified results (side effects) is likely to be more serious than you think.
Http://bbs.chinaunix.net/thread-1805254-1-1.html
Setup issues with sort_buffer_size parameter size in MySQL