14.21. MySQL Connector
The MySQL connector allows querying and creating tables in an external MySQL database. This can be used to join data between different systems like MySQL and Hive, or between two different MySQL instances.
To configure the MySQL connector, create a catalog properties file
etc/catalog named, for example,
mount the MySQL connector as the
Create the file with the following contents, replacing the
connection properties as appropriate for your setup:
connector.name=mysql connection-url=jdbc:mysql://example.net:3306 connection-user=root connection-password=secret
Multiple MySQL Servers
You can have as many catalogs as you need, so if you have additional
MySQL servers, simply add another properties file to
with a different name (making sure it ends in
example, if you name the property file
will create a catalog named
sales using the configured connector.
The MySQL connector provides a schema for every MySQL database.
You can see the available MySQL databases by running
SHOW SCHEMAS FROM mysql;
If you have a MySQL database named
web, you can view the tables
in this database by running
SHOW TABLES FROM mysql.web;
You can see a list of the columns in the
clicks table in the
using either of the following:
DESCRIBE mysql.web.clicks; SHOW COLUMNS FROM mysql.web.clicks;
Finally, you can access the
clicks table in the
SELECT * FROM mysql.web.clicks;
If you used a different name for your catalog properties file, use
that catalog name instead of
mysql in the above examples.
MySQL connector supports table and column statistics. The table-level statistics
are based on MySQL’s
INFORMATION_SCHEMA.TABLES table. The column-level
statistics are based on MySQL’s index statistics
table. The connector can return column-level statistics only when the column is
the first column in some index.
MySQL Database can automatically update its table and index statistics. In some cases, you may want to force statistics update (e.g. after creating new index or after changing data in the table). You can do that by executing the following statement in MySQL Database.
ANALYZE TABLE table_name;
MySQL and Presto may use statistics information in different ways. For this reason, the accuracy of table and column statistics returned by the MySQL connector might be lower than than that of others connectors.
Improving Statistics Accuracy
You can improve statistics accuracy with histogram statistics (available since MySQL 8.0). To create histogram statistics execute the following statement in MySQL Database.
ANALYZE TABLE table_name UPDATE HISTOGRAM ON column_name1, column_name2, ...;
Please refer to MySQL documentation for information about options, limitations and additional considerations.
Table Statistics Configuration Properties
||Enables table and column statistics.||
||Duration for which table and column statistics are cached.||
||Cache the fact that table statistics were not available.||