mysql SQL SERVER 的算法

Filesort Probes

http://dev.mysql.com/doc/refman/5.7/en/dba-dtrace-ref-filesort.html

http://dev.mysql.com/doc/refman/5.7/en/order-by-optimization.html

index-merge

http://dev.mysql.com/doc/refman/5.7/en/index-merge-optimization.html