ClickHouse Connector

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

Configuration

To configure the ClickHouse connector, create a catalog properties fileetc/catalog/clickhouse.properties, replace the connection properties as needed for your setup:

connector.name=clickhouse
connection-url=jdbc:clickhouse:host1:8123:/default
connection-user=default
connection-password=

Multiple ClickHouse servers

The ClickHouse connector can't access more than one database using a single catalog. If you have multiple ClickHouse servers you need to configure one catalog for each instance. To add another catalog:

Add another properties file to etc/catalog
Save it with a different name that ends in .properties

For example, if you name the property file sales.properties, Presto 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 clichouse;

If you have a ClickHouse database named web, run SHOW TABLES to view the tables in this database:

SHOW TABLES FROM clichouse.web;

Run DESCRIBE or SHOW COLUMNS to list the columns in the clicks table in the web databases:

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

Run SELECT to access the clicks table in the web database:

SELECT * FROM clichouse.web.clicks;

Note:

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