Question

我创建了一个mysql表，并将哈希分区如下。

      mysql> CREATE TABLE employees (
               id INT NOT NULL,
               fname VARCHAR(30),
               lname VARCHAR(30),
               hired DATE NOT NULL DEFAULT '1970-01-01',
               separated DATE NOT NULL DEFAULT '9999-12-31',
               job_code INT,
               store_id INT,
               PRIMARY KEY(id)
             )
             PARTITION BY HASH(id)
             PARTITIONS 10;

成功创建表后，我将值1（插入store_id）插入到下面的表中

  mysql>INSERT INTO employees (store_id) values (1);

现在我不明白这个1的值会在哪里进入？进入哪个分区（p0，p1，p2 ...... p10）store_id值为1？我以为它会进入p0。但事实并非如此。见下文我这样检查了

  mysql>SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH,DATA_LENGTH FROM INFORMATION_SCHEMA.PARTITIONS WHERE TABLE_NAME LIKE 'employees';

它已显示值已进入p1.see

   mysql>
        +------------+----------------+------------+----------------+-------------+
        | TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
        +------------+----------------+------------+----------------+-------------+
        | employees  | p0             |          0 |              0 |       16384 |
        | employees  | p1             |          1 |          16384 |       16384 |
        | employees  | p2             |          0 |              0 |       16384 |
        | employees  | p3             |          0 |              0 |       16384 |
        | employees  | p4             |          0 |              0 |       16384 |
        | employees  | p5             |          0 |              0 |       16384 |
        | employees  | p6             |          0 |              0 |       16384 |
        | employees  | p7             |          0 |              0 |       16384 |
        | employees  | p8             |          0 |              0 |       16384 |
        | employees  | p9             |          0 |              0 |       16384 |
        +------------+----------------+------------+----------------+-------------+

我不知道为什么它再次被插入p1.tested ..我这次插入值2 ...

       mysql> INSERT INTO employees (store_id) values (2);

它已进入p2。

         +------------+----------------+------------+----------------+-------------+
         | TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
         +------------+----------------+------------+----------------+-------------+
         | employees  | p0             |          0 |              0 |       16384 |
         | employees  | p1             |          1 |          16384 |       16384 |
         | employees  | p2             |          1 |          16384 |       16384 |
         | employees  | p3             |          0 |              0 |       16384 |
         | employees  | p4             |          0 |              0 |       16384 |
         | employees  | p5             |          0 |              0 |       16384 |
         | employees  | p6             |          0 |              0 |       16384 |
         | employees  | p7             |          0 |              0 |       16384 |
         | employees  | p8             |          0 |              0 |       16384 |
         | employees  | p9             |          0 |              0 |       16384 |
         +------------+----------------+------------+----------------+-------------+

为什么将值插入到不同的分区中？是否存在散列分区遵循的规则？有趣的是它离开p0并开始插入p1？解释

Answer 1

如果this解释适用于您的MySQL版本，则可以通过以下方式找到分区号：MOD([Your input],[Number of partitions])。

在你的情况下，第一行可能有id = 1，计算将是MOD(1,10) = 1.行进入分区1（id = 2进入分区2）

如何将值插入到Mysql散列分区表中？

1 个答案: