1、Handling of NULL with RANGE partitioning
CREATE TABLE t1 (
c1 INT,
c2 VARCHAR(20)
)
PARTITION BY RANGE(c1) (
PARTITION p0 VALUES LESS THAN (0),
PARTITION p1 VALUES LESS THAN (10),
PARTITION p2 VALUES LESS THAN MAXVALUE
);
CREATE TABLE t2 (
c1 INT,
c2 VARCHAR(20)
)
PARTITION BY RANGE(c1) (
PARTITION p0 VALUES LESS THAN (-5),
PARTITION p1 VALUES LESS THAN (0),
PARTITION p2 VALUES LESS THAN (10),
PARTITION p3 VALUES LESS THAN MAXVALUE);
(root@33306) [test]> SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
-> FROM INFORMATION_SCHEMA.PARTITIONS
-> WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME LIKE 't_';
+------------+----------------+------------+----------------+-------------+
| TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
+------------+----------------+------------+----------------+-------------+
| t1 | p0 | 0 | 0 | 16384 |
| t1 | p1 | 0 | 0 | 16384 |
| t1 | p2 | 0 | 0 | 16384 |
| t2 | p0 | 0 | 0 | 16384 |
| t2 | p1 | 0 | 0 | 16384 |
| t2 | p2 | 0 | 0 | 16384 |
| t2 | p3 | 0 | 0 | 16384 |
(root@33306) [test]> INSERT INTO t1 VALUES (NULL, 'mothra');
Query OK, 1 row affected (0.01 sec)
(root@33306) [test]> INSERT INTO t2 VALUES (NULL, 'mothra');
Query OK, 1 row affected (0.01 sec)
(root@33306) [test]> SELECT * FROM t1;
+------+--------+
| c1 | c2 |
+------+--------+
| NULL | mothra |
+------+--------+
1 row in set (0.00 sec)
(root@33306) [test]> SELECT * FROM t2;
+------+--------+
| c1 | c2 |
+------+--------+
| NULL | mothra |
+------+--------+
1 row in set (0.00 sec)
(root@33306) [test]> SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
-> FROM INFORMATION_SCHEMA.PARTITIONS
-> WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME LIKE 't_';
+------------+----------------+------------+----------------+-------------+
| TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
+------------+----------------+------------+----------------+-------------+
| t1 | p0 | 1 | 16384 | 16384 |
| t1 | p1 | 0 | 0 | 16384 |
| t1 | p2 | 0 | 0 | 16384 |
| t2 | p0 | 1 | 16384 | 16384 |
| t2 | p1 | 0 | 0 | 16384 |
| t2 | p2 | 0 | 0 | 16384 |
| t2 | p3 | 0 | 0 | 16384 |
可以发现是NULL值放在p0 分区里面了
如果是date类型的列呢，再次测试
(root@33306) [test]> CREATE TABLE tndate (
-> id INT,
-> dt DATE
-> )
-> PARTITION BY RANGE( YEAR(dt) ) (
-> PARTITION p0 VALUES LESS THAN (1990),
-> PARTITION p1 VALUES LESS THAN (2000),
-> PARTITION p2 VALUES LESS THAN MAXVALUE
-> );
(root@33306) [test]> insert into tndate VALUES(1,NULL);
Query OK, 1 row affected (0.00 sec)
(root@33306) [test]> SELECT *FROM TNDATE;
+------+------+
| id | dt |
+------+------+
| 1 | NULL |
+------+------+
1 row in set (0.00 sec)
(root@33306) [test]> SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
-> FROM INFORMATION_SCHEMA.PARTITIONS
-> WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME ='tndate';
+------------+----------------+------------+----------------+-------------+
| TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
+------------+----------------+------------+----------------+-------------+
| tndate | p0 | 1 | 16384 | 16384 |
| tndate | p1 | 0 | 0 | 16384 |
| tndate | p2 | 0 | 0 | 16384 |
+------------+----------------+------------+----------------+-------------+
3 rows in set (0.00 sec)
结果：可以发现数据存储在P0的分区里面
2、Handling of NULL with LIST partitioning
mysql> CREATE TABLE ts1 (
c1 INT,
c2 VARCHAR(20)
)
PARTITION BY LIST(c1) (
PARTITION p0 VALUES IN (0, 3, 6),
PARTITION p1 VALUES IN (1, 4, 7),
PARTITION p2 VALUES IN (2, 5, 8)
);
(root@33306) [test]> INSERT INTO ts1 VALUES (9, 'mothra');
ERROR 1526 (HY000): Table has no partition for value 9
(root@33306) [test]>
(root@33306) [test]>
(root@33306) [test]> INSERT INTO ts1 VALUES (NULL, 'mothra');
ERROR 1526 (HY000): Table has no partition for value NULL
(root@33306) [test]>
从上面可以看出只有0-8 可以插入到表ts1中，对于0-8以外和NULL值是无法插入其中
NULL值可以作为一个list 值放在list表中
CREATE TABLE ts2 (
c1 INT,
c2 VARCHAR(20)
)
PARTITION BY LIST(c1) (
PARTITION p0 VALUES IN (0, 3, 6),
PARTITION p1 VALUES IN (1, 4, 7),
PARTITION p2 VALUES IN (2, 5, 8),
PARTITION p3 VALUES IN (NULL)
);
CREATE TABLE ts3 (
c1 INT,
c2 VARCHAR(20)
)
PARTITION BY LIST(c1) (
PARTITION p0 VALUES IN (0, 3, 6),
PARTITION p1 VALUES IN (1, 4, 7, NULL),
PARTITION p2 VALUES IN (2, 5, 8)
);
(root@33306) [test]> INSERT INTO ts2 VALUES (NULL, 'mothra');
Query OK, 1 row affected (0.00 sec)
(root@33306) [test]> INSERT INTO ts3 VALUES (NULL, 'mothra');
Query OK, 1 row affected (0.01 sec)
SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
FROM INFORMATION_SCHEMA.PARTITIONS
WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME ='tndate';
(root@33306) [test]> SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
-> FROM INFORMATION_SCHEMA.PARTITIONS
-> WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME LIKE 'ts_';
+------------+----------------+------------+----------------+-------------+
| TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
+------------+----------------+------------+----------------+-------------+
| ts1 | p0 | 0 | 0 | 16384 |
| ts1 | p1 | 0 | 0 | 16384 |
| ts1 | p2 | 0 | 0 | 16384 |
| ts2 | p0 | 0 | 0 | 16384 |
| ts2 | p1 | 0 | 0 | 16384 |
| ts2 | p2 | 0 | 0 | 16384 |
| ts2 | p3 | 1 | 16384 | 16384 |
| ts3 | p0 | 0 | 0 | 16384 |
| ts3 | p1 | 1 | 16384 | 16384 |
| ts3 | p2 | 0 | 0 | 16384 |
+------------+----------------+------------+----------------+-------------+
10 rows in set (0.00 sec)
空值插入到对应的分区表中区
3、Handling of NULL with HASH and KEY partitioning
CREATE TABLE th (
c1 INT,
c2 VARCHAR(20)
)
PARTITION BY HASH(c1)
PARTITIONS 2;
INSERT INTO th VALUES (NULL, 'mothra'), (0, 'gigan');
(root@33306) [test]> SELECT * FROM th;
+------+--------+
| c1 | c2 |
+------+--------+
| NULL | mothra |
| 0 | gigan |
+------+--------+
2 rows in set (0.00 sec)
SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
FROM INFORMATION_SCHEMA.PARTITIONS
WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME ='th';
(root@33306) [test]> SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
-> FROM INFORMATION_SCHEMA.PARTITIONS
-> WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME ='th';
+------------+----------------+------------+----------------+-------------+
| TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
+------------+----------------+------------+----------------+-------------+
| th | p0 | 2 | 8192 | 16384 |
| th | p1 | 0 | 0 | 16384 |
+------------+----------------+------------+----------------+-------------+
2 rows in set (0.00 sec)
可以看到对于hash 分区表，NULL值是放在p0里面
结论：对于range 和hash分区，null值会放在分区表的首个分区p0里面
对于list 分区，NULL值是作为一个list值 放在分区列表中