EF MySql:Specified key was too long; max key length is 767 bytes解决方案

[DbConfigurationType(typeof(MySqlEFConfiguration))]//添加特性
public partial class Model1 : DbContext
{
    public Model1()
        : base("name=Model1")
    {
    } 
    public DbSet<text123> text123 { get; set; } 
}