14. HASH & amp; KEY and mysqlhash of mysql partitions

14. mysql partition HASH & KEY, mysqlhash

1. hash partition ps: I personally think the HASH PARTITION is very good and powerful, and the simple distribution is extremely even to CREATE an instance: CREATE TABLE HASH_EMP (tid int, tname char (255) PARTITION BY HASH (tid) PARTITIONS 8; Perform hash partitioning on the tid of hash_emp, and query the data distribution of the partition in eight zones: select partition_name, partition_expression, partition_description, table_rows from partition where table_schema = schema () and table_name = 'hash _ emp'; + ------------------ + ---------------------- + ------------ ----------- + ------------ + | Partition_name | partition_expression | partition_description | table_rows | + ---------------- + tables + ------------ + | p0 | tid | NULL | 0 | p1 | tid | NULL | 0 | | p2 | tid | NULL | 0 | p3 | tid | NULL | 0 | p4 | tid | NULL | 0 | p5 | tid | NULL | 0 | p6 | tid | NULL | 0 | p7 | tid | NULL | 0 | + -------------- + ------ ---------------- + --------------------- + ------------ + Create an event to continuously write data. Test distribution: create event hash_emp_event on scheduler every 1 second do insert into hash_emp values (NULL, now (); set GLOBAL event_scheduler = 1; // enable the scheduler to view the partition data distribution again: + ---------------- + ---------------------- + ----------------------- + ------------ + | partition_name | partition_expression | partition_description | table_rows | + --- ------------- + ---------------------- + ----------------------- + ------------ + | P0 | tid | NULL | 41 | p1 | tid | NULL | 42 | p2 | tid | NULL | 42 | p3 | tid | NULL | 42 | p4 | tid | NULL | 42 | p5 | tid | NULL | 42 | p6 | tid | NULL | 42 | p7 | tid | NULL | 42 | + ---------------- + ---------------------- + ------------------------- + ------------ + can be seen, hash distribution is extremely even:; 2. key partition PS: the so-called key partition refers to mysql Use the primary KEY or unique TABLE creation for PARTITION management to CREATE an instance: create table KEY_EMP (tid int, tname char (255) partition by key (tid) PARTITIONS 8; PS :: because it is similar to hash, too many tests will not be conducted !!! 3. sub-partition PS: As the name implies, it is to re-create a partition on the partition PS: supports the sub-partition mode range | list, both of them can support creating instances BY hash or list subpartitions: create table ZI_EMP (tid int, tname char (255) partition by range (tid) subpartition by hash (tid) SUBPARTITIONS 2 (PARTITION p0 values less than (1990), PARTITION p1 values less than (2028), PARTITION p2 values less than (MAXVALUE )); divide zi_emp into three range partitions. Each partition is divided into two subpartitions. If so, the following partition structure is available: + partition + ------------ + | partition_name | partition_expression | partition_description | table_rows | + ---------------- + partition + ---------- + | p0 | tid | 1990 | 0 | p0 | tid | 1990 | 0 | p1 | tid | 2028 | 0 | p1 | tid | 2028 | 0 | p2 | tid | MAXVALUE | 0 | p2 | tid | MAXVALUE | 0 | + ---------------- + ---------------------- + ----------------------- + ------------ + that is to say, if tid is less than 1990, the data is allocated to the p0 subpartition by hash.

 

MYSQL hash decryption root: iammysqladmin
For details about how to use hash in mysql, see MySQL help file. chm

MD5 (string)
Calculate the MD5 checksum value of a string as a 32-length hexadecimal number. The return example is used as the hash key.
Mysql> select MD5 ("testing ")
-> 'Ae2b1fca515949e5d54fb22b8ed95575'

RSA Data Security Company MD5 message digest algorithm