ClickHouse connector#
The ClickHouse connector allows querying tables in an external Yandex ClickHouse instance. This can be used to query data in the databases on that instance, or combine it with other data from different catalogs accessing ClickHouse or any other supported data source.
Configuration#
The connector can query a ClickHouse instance. Create a catalog properties file
that specifies the ClickHouse connector by setting the connector.name to
clickhouse.
For example, to access an instance as myclickhouse, create the file
etc/catalog/myclickhouse.properties. Replace the connection properties as
appropriate for your setup:
connector.name=clickhouse
connection-url=jdbc:clickhouse://host1:8123/
connection-user=exampleuser
connection-password=examplepassword
Multiple ClickHouse servers#
If you have multiple ClickHouse instances you need to configure one catalog for each instance. To add another catalog:
Add another properties file to
etc/catalogSave it with a different name that ends in
.properties
For example, if you name the property file sales.properties, Trino uses the
configured connector to create a catalog named sales.
Querying ClickHouse#
The ClickHouse connector provides a schema for every ClickHouse database.
run SHOW SCHEMAS to see the available ClickHouse databases:
SHOW SCHEMAS FROM myclickhouse;
If you have a ClickHouse database named web, run SHOW TABLES to view the
tables in this database:
SHOW TABLES FROM myclickhouse.web;
Run DESCRIBE or SHOW COLUMNS to list the columns in the clicks table in the
web databases:
DESCRIBE myclickhouse.web.clicks;
SHOW COLUMNS FROM clickhouse.web.clicks;
Run SELECT to access the clicks table in the web database:
SELECT * FROM myclickhouse.web.clicks;
Note
If you used a different name for your catalog properties file, use
that catalog name instead of myclickhouse in the above examples.
Limitations#
The following SQL statements aren’t supported: