Migrate Data from MySQL to TiDB

Use the mydumper/loader tool to export and import all the data

You can use mydumper to export data from MySQL and loader to import the data into TiDB.

Note:

Although TiDB also supports the official mysqldump tool from MySQL for data migration, it is not recommended to use it. Its performance is much lower than mydumper / loader and it takes much time to migrate large amounts of data. It is important to use the mydumper provided by TiDB and not the upstream mydumper version. See mydumper for more information.

Mydumper and loader can be downloaded as part of Enterprise Tools.

Export data from MySQL

Use the mydumper tool to export data from MySQL by using the following command:

./bin/mydumper -h 127.0.0.1 -P 3306 -u root -t 16 -F 64 -B test -T t1,t2 --skip-tz-utc -o ./var/test

In this command,

• -B test: means the data is exported from the test database.
• -T t1,t2: means only the t1 and t2 tables are exported.
• -t 16: means 16 threads are used to export the data.
• -F 64: means a table is partitioned into chunks and one chunk is 64MB.
• --skip-tz-utc: the purpose of adding this parameter is to ignore the inconsistency of time zone setting between MySQL and the data exporting machine and to disable automatic conversion.

Note:

On the Cloud platforms which require the super privilege, such as on the Amazon RDS, add the --no-locks parameter to the command. If not, you might get the error message that you don’t have the privilege.

Import data to TiDB

Use loader to import the data from MySQL to TiDB. See Loader instructions for more information.

./bin/loader -h 127.0.0.1 -u root -P 4000 -t 32 -d ./var/test

After the data is imported, you can view the data in TiDB using the MySQL client:

mysql -h127.0.0.1 -P4000 -uroot

mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t1             |
| t2             |
+----------------+

mysql> select * from t1;
+----+------+
| id | age  |
+----+------+
|  1 |    1 |
|  2 |    2 |
|  3 |    3 |
+----+------+

mysql> select * from t2;
+----+------+
| id | name |
+----+------+
|  1 | a    |
|  2 | b    |
|  3 | c    |
+----+------+

Best practice

To migrate data quickly, especially for huge amount of data, you can refer to the following recommendations.

• Keep the exported data file as small as possible and it is recommended keep it within 64M. You can use the -F parameter to set the value.
• You can adjust the -t parameter of loader based on the number and the load of TiKV instances. For example, if there are three TiKV instances, -t can be set to 3 * (1 ~ n). If the load of TiKV is too high and the log backoffer.maxSleep 15000ms is exceeded is displayed many times, decrease the value of -t; otherwise, increase it.

A sample and the configuration

• The total size of the exported files is 214G. A single table has 8 columns and 2 billion rows.
• The cluster topology:
  • 12 TiKV instances: 4 nodes, 3 TiKV instances per node
  • 4 TiDB instances
  • 3 PD instances
• The configuration of each node:
  • CPU: Intel Xeon E5-2670 v3 @ 2.30GHz
  • 48 vCPU [2 x 12 physical cores]
  • Memory: 128G
  • Disk: sda [raid 10, 300G] sdb[RAID 5, 2T]
  • Operating System: CentOS 7.3
• The -F parameter of mydumper is set to 16 and the -t parameter of loader is set to 64.

Results: It takes 11 hours to import all the data, which is 19.4G/hour.