MySQL connector#

The MySQL connector allows querying and creating tables in an external MySQL instance. This can be used to join data between different systems like MySQL and Hive, or between two different MySQL instances.

Requirements#

To connect to MySQL, you need:

  • MySQL 5.7, 8.0 or higher.

  • Network access from the Trino coordinator and workers to MySQL. Port 3306 is the default port.

Configuration#

To configure the MySQL connector, create a catalog properties file in etc/catalog named, for example, mysql.properties, to mount the MySQL connector as the mysql catalog. 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

The connection-url defines the connection information and parameters to pass to the MySQL JDBC driver. The supported parameters for the URL are available in the MySQL Developer Guide.

For example, the following connection-url allows you to configure the JDBC driver to interpret time values based on UTC as a timezone on the server, and serves as a workaround for a known issue.

connection-url=jdbc:mysql://example.net:3306?serverTimezone=UTC

The connection-user and connection-password are typically required and determine the user credentials for the connection, often a service user. You can use secrets to avoid actual values in the catalog properties files.

General configuration properties#

The following table describes general configuration properties for the connector:

Property name

Description

Default value

case-insensitive-name-matching

Support case insensitive database and collection names

False

case-insensitive-name-matching.cache-ttl

1 minute

metadata.cache-ttl

Duration for which metadata, including table and column statistics, is cached

0 (disabled caching)

metadata.cache-missing

Cache the fact that metadata, including table and column statistics, is not available

False

Non-transactional INSERT#

The connector supports adding rows using INSERT statements. By default, data insertion is performed by writing data to a temporary table. You can skip this step to improve performance and write directly to the target table. Set the insert.non-transactional-insert.enabled catalog property or the corresponding non_transactional_insert catalog session property to true.

Note that with this property enabled, data can be corrupted in rare cases where exceptions occur during the insert operation. With transactions disabled, no rollback can be performed.

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 etc/catalog with a different name, making sure it ends in .properties. For example, if you name the property file sales.properties, Trino creates a catalog named sales using the configured connector.

Type mapping#

Decimal type handling#

DECIMAL types with precision larger than 38 can be mapped to a Trino DECIMAL by setting the decimal-mapping configuration property or the decimal_mapping session property to allow_overflow. The scale of the resulting type is controlled via the decimal-default-scale configuration property or the decimal-rounding-mode session property. The precision is always 38.

By default, values that require rounding or truncation to fit will cause a failure at runtime. This behavior is controlled via the decimal-rounding-mode configuration property or the decimal_rounding_mode session property, which can be set to UNNECESSARY (the default), UP, DOWN, CEILING, FLOOR, HALF_UP, HALF_DOWN, or HALF_EVEN (see RoundingMode).

General configuration properties#

The following properties can be used to configure how data types from the connected data source are mapped to Trino data types and how the metadata is cached in Trino.

Property name

Description

Default value

unsupported-type-handling

Configure how unsupported column data types are handled:

  • IGNORE, column is not accessible.

  • CONVERT_TO_VARCHAR, column is converted to unbounded VARCHAR.

The respective catalog session property is unsupported_type_handling.

IGNORE

jdbc-types-mapped-to-varchar

Allow forced mapping of comma separated lists of data types to convert to unbounded VARCHAR

Querying MySQL#

The MySQL connector provides a schema for every MySQL database. You can see the available MySQL databases by running SHOW SCHEMAS:

SHOW SCHEMAS FROM mysql;

If you have a MySQL database named web, you can view the tables in this database by running SHOW TABLES:

SHOW TABLES FROM mysql.web;

You can see a list of the columns in the clicks table in the web database using either of the following:

DESCRIBE mysql.web.clicks;
SHOW COLUMNS FROM mysql.web.clicks;

Finally, you can access the clicks table in the web database:

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.

Pushdown#

The connector supports pushdown for a number of operations:

Aggregate pushdown for the following functions:

SQL support#

The connector provides read access and write access to data and metadata in the MySQL database. In addition to the globally available and read operation statements, the connector supports the following statements:

SQL DELETE#

If a WHERE clause is specified, the DELETE operation only works if the predicate in the clause can be fully pushed down to the data source.