使用如下sql語句創(chuàng)建表：

create table t(
name varchar(20) not null,
age tinyint unsigned,
created_at datetime
) partition by range(month(created_at))(
partition p1 values less than(2),
partition p2 values less than(3),
partition p3 values less than(4),
partition p4 values less than(5),
partition p5 values less than(6),
partition p6 values less than(7),
partition p7 values less than(8),
partition p8 values less than(9),
partition p9 values less than(10),
partition p10 values less than(11),
partition p11 values less than(12),
partition p12 values less than(13)
);

插入數(shù)據(jù)查看分區(qū)的存儲情況如下：

select partition_name, PARTITION_DESCRIPTION, PARTITION_EXPRESSION, table_rows from information_schema.partitions where table_name = 't'

但是在查詢數(shù)據(jù)時總是需要查詢所有分區(qū)

explain select * from t where created_at < '2018-04-01';

正常情況下不應(yīng)該只查詢前3個分區(qū)嗎，為什么在這里會掃描所有分區(qū)呢？