生成大量数据来测试：
create table t1 (id int not null primary key auto_increment,age int,name varchar(20),createtime date);
create index idx_age_name_create on t1(age,name,createtime);
vi create-data.sh
#!/bin/bash
i=1;
MAX_INSERT_ROW_COUNT=$1;
while [ $i -le $MAX_INSERT_ROW_COUNT ]
do mysql -uroot -p123456 test -e "insert into t1 (name,age,createtime) values ('HELLO$i',$i % 99,NOW());"
d=$(date +%M-%d\ %H\:%m\:%S)
echo "INSERT HELLO $i @@ $d"
i=$(($i+1))
sleep 0.05
done
