一、MySql官网文档解释
在**mysql5.***中描述如下
Different limits related to tables and indexes. For example, the maximum number of ordered indexes in the cluster is determined by MaxNoOfOrderedIndexes, and the maximum number of ordered indexes per table is 16.
**mysql8.***中描述如下
A table can contain a maximum of 64 secondary indexes.A maximum of 16 columns is permitted for multicolumn indexes. Exceeding the limit returns an error.
ERROR 1070 (42000): Too many key parts specified; max 16 parts allowed