MySQL connector

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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, example.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:

text

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 require encrypted connections to the MySQL server:

text

connection-url=jdbc:mysql://example.net:3306?sslMode=REQUIRED

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

(mysql-tls)=

Connection security

If you have TLS configured with a globally-trusted certificate installed on your data source, you can enable TLS between your cluster and the data source by appending a parameter to the JDBC connection string set in the connection-url catalog configuration property.

For example, with version 8.0 of MySQL Connector/J, use the sslMode parameter to secure the connection with TLS. By default the parameter is set to PREFERRED which secures the connection if enabled by the server. You can also set this parameter to REQUIRED which causes the connection to fail if TLS is not established.

You can set the sslMode parameter in the catalog configuration file by appending it to the connection-url configuration property:

properties

connection-url=jdbc:mysql://example.net:3306/?sslMode=REQUIRED

For more information on TLS configuration options, see the MySQL JDBC security documentation.

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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.

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(mysql-fte-support)=

Fault-tolerant execution support

The connector supports {doc}/admin/fault-tolerant-execution of query processing. Read and write operations are both supported with any retry policy.

Table properties

Table property usage example:

CREATE TABLE person (
  id INT NOT NULL,
  name VARCHAR,
  age INT,
  birthday DATE 
)
WITH (
  primary_key = ARRAY['id']
);

The following are supported MySQL table properties:

:::{list-table} :widths: 30, 10, 60 :header-rows: 1

- Property name
- Required
- Description
- primary_key
- No
- The primary key of the table, can choose multi columns as the table primary key. All key columns must be defined as NOT NULL. :::

(mysql-type-mapping)=

Type mapping

Because Trino and MySQL each support types that the other does not, this connector {ref}modifies some types <type-mapping-overview> when reading or writing data. Data types may not map the same way in both directions between Trino and the data source. Refer to the following sections for type mapping in each direction.

MySQL to Trino type mapping

The connector maps MySQL types to the corresponding Trino types following this table:

:::{list-table} MySQL to Trino type mapping :widths: 30, 30, 40 :header-rows: 1

- MySQL database type
- Trino type
- Notes
- BIT
- BOOLEAN
- BOOLEAN
- TINYINT
- TINYINT
- TINYINT
- TINYINT UNSIGNED
- SMALLINT
- SMALLINT
- SMALLINT
- SMALLINT UNSIGNED
- INTEGER
- INTEGER
- INTEGER
- INTEGER UNSIGNED
- BIGINT
- BIGINT
- BIGINT
- BIGINT UNSIGNED
- DECIMAL(20, 0)
- DOUBLE PRECISION
- DOUBLE
- FLOAT
- REAL
- REAL
- REAL
- DECIMAL(p, s)
- DECIMAL(p, s) or NUMBER
- Maps to Trino DECIMAL when p ≤ 38. Otherwise, maps to NUMBER.
- CHAR(n)
- CHAR(n)
- VARCHAR(n)
- VARCHAR(n)
- TINYTEXT
- VARCHAR(255)
- TEXT
- VARCHAR(65535)
- MEDIUMTEXT
- VARCHAR(16777215)
- LONGTEXT
- VARCHAR
- ENUM(n)
- VARCHAR(n)
- BINARY, VARBINARY, TINYBLOB, BLOB, MEDIUMBLOB, LONGBLOB
- VARBINARY
- JSON
- JSON
- DATE
- DATE
- TIME(n)
- TIME(n)
- DATETIME(n)
- TIMESTAMP(n)
- TIMESTAMP(n)
- TIMESTAMP(n) WITH TIME ZONE

:::

No other types are supported.

Trino to MySQL type mapping

The connector maps Trino types to the corresponding MySQL types following this table:

:::{list-table} Trino to MySQL type mapping :widths: 30, 30, 40 :header-rows: 1

- Trino type
- MySQL type
- Notes
- BOOLEAN
- TINYINT
- TINYINT
- TINYINT
- SMALLINT
- SMALLINT
- INTEGER
- INTEGER
- BIGINT
- BIGINT
- REAL
- REAL
- DOUBLE
- DOUBLE PRECISION
- DECIMAL(p, s)
- DECIMAL(p, s)
- CHAR(n)
- CHAR(n)
- VARCHAR(n)
- VARCHAR(n)
- JSON
- JSON
- DATE
- DATE
- TIME(n)
- TIME(n)
- TIMESTAMP(n)
- DATETIME(n)
- TIMESTAMP(n) WITH TIME ZONE
- TIMESTAMP(n)

:::

No other types are supported.

Timestamp type handling

MySQL TIMESTAMP types are mapped to Trino TIMESTAMP WITH TIME ZONE. To preserve time instants, Trino sets the session time zone of the MySQL connection to match the JVM time zone. As a result, error messages similar to the following example occur when a timezone from the JVM does not exist on the MySQL server:

com.mysql.cj.exceptions.CJException: Unknown or incorrect time zone: 'UTC'

To avoid the errors, you must use a time zone that is known on both systems, or install the missing time zone on the MySQL server.

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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 example;

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

SHOW TABLES FROM example.web;

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

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

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

SELECT * FROM example.web.clicks;

If you used a different name for your catalog properties file, use that catalog name instead of example in the above examples.

(mysql-sql-support)=

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 features:

, see also
, see also
, see also
, see also

(mysql-insert)=

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(mysql-update)=

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(mysql-delete)=

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(mysql-merge)=

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(mysql-procedures)=

Procedures

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(mysql-table-functions)=

Table functions

The connector provides specific {doc}table functions </functions/table> to access MySQL.

(mysql-query-function)=

`query(varchar) -> table`

The query function allows you to query the underlying database directly. It requires syntax native to MySQL, because the full query is pushed down and processed in MySQL. This can be useful for accessing native features which are not available in Trino or for improving query performance in situations where running a query natively may be faster.

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For example, query the example catalog and group and concatenate all employee IDs by manager ID:

SELECT
  *
FROM
  TABLE(
    example.system.query(
      query => 'SELECT
        manager_id, GROUP_CONCAT(employee_id)
      FROM
        company.employees
      GROUP BY
        manager_id'
    )
  );

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Performance

The connector includes a number of performance improvements, detailed in the following sections.

(mysql-table-statistics)=

Table statistics

The MySQL connector can use {doc}table and column statistics </optimizer/statistics> for {doc}cost based optimizations </optimizer/cost-based-optimizations>, to improve query processing performance based on the actual data in the data source.

The statistics are collected by MySQL and retrieved by the connector.

The table-level statistics are based on MySQL's INFORMATION_SCHEMA.TABLES table. The column-level statistics are based on MySQL's index statistics INFORMATION_SCHEMA.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, for example after creating new index, or after changing data in the table. You can do that by executing the following statement in MySQL Database.

text

ANALYZE TABLE table_name;

:::{note} MySQL and Trino 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 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.

text

ANALYZE TABLE table_name UPDATE HISTOGRAM ON column_name1, column_name2, ...;

Refer to MySQL documentation for information about options, limitations and additional considerations.

(mysql-pushdown)=

Pushdown

The connector supports pushdown for a number of operations:

{ref}join-pushdown
{ref}limit-pushdown
{ref}topn-pushdown

{ref}Aggregate pushdown <aggregation-pushdown> for the following functions:

{func}avg
{func}count
{func}max
{func}min
{func}sum
{func}stddev
{func}stddev_pop
{func}stddev_samp
{func}variance
{func}var_pop
{func}var_samp

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