Sharded Table Management

Last updated: 2019-12-06 16:41:57

    This documents takes a sharded table as an example to describe some simple database operations in TDSQL.

    Creating a Table

    • For more information on the differences between sharded, non-sharded, and broadcast tables, see Table Overview.
    • For selection restrictions on the shardkey, see Shardkey Overview.
    • When creating a sharded table, the shardkey needs to be specified. Below is the sample code:
      mysql> create table test1(id int primary key,name varchar(20),addr varchar(20))shardkey=id;
      Query OK,0 rows affected(0.15 sec)

    Inserting Data

    The insert field must include the shardkey; otherwise, the operation will be refused.

    Insert data into the table just created. Below is the sample code:

    mysql> insert into test1(id,name);
    Query OK,1 rows affected(0.08 sec)
    mysql> insert into test3(name,addr) values('example','shenzhen');
    ERROR 7013 (HY000): Proxy ERROR:get_shardkeys return error

    Querying Data

    When you query data, you are recommended to include the shardkey, so that the distributed route will be automatically redirected to the corresponding shard, achieving the highest efficiency; otherwise, the distributed system will automatically scan the entire table and then aggregate the results at the gateway, which compromises the efficiency.

    Below is the sample code for data query:

    mysql> select id from test1 where id=1;

    Deleting Data

    A "where" condition must be included in a "DELETE" operation, and you are recommended to include the shardkey in the "where" condition.

    Below is the sample code for data deletion:

    mysql> delete from test1 where id=1;
    Query OK, 1 row affected (0.02 sec)

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