The ClickHouse connector allows querying tables in an external Yandex ClickHouse server. This can be used to query data in the databases on that server, or combine it with other data from different catalogs accessing ClickHouse or any other supported data source.
To connect to a ClickHouse server, you need:
ClickHouse version 20.8 or higher.
Network access from the Trino coordinator and workers to the ClickHouse server. Port 8123 is the default port.
The connector can query a ClickHouse server. Create a catalog properties file
that specifies the ClickHouse connector by setting the
For example, to access a server 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 servers you need to configure one catalog for each server. To add another catalog:
Add another properties file to
Save it with a different name that ends in
For example, if you name the property file
sales.properties, Trino uses the
configured connector to create a catalog named
The ClickHouse connector provides a schema for every ClickHouse database.
SHOW SCHEMAS to see the available ClickHouse databases:
SHOW SCHEMAS FROM myclickhouse;
If you have a ClickHouse database named
SHOW TABLES to view the
tables in this database:
SHOW TABLES FROM myclickhouse.web;
SHOW COLUMNS to list the columns in the
DESCRIBE myclickhouse.web.clicks; SHOW COLUMNS FROM clickhouse.web.clicks;
SELECT to access the
clicks table in the
SELECT * FROM myclickhouse.web.clicks;
If you used a different name for your catalog properties file, use
that catalog name instead of
myclickhouse in the above examples.
Table property usage example:
CREATE TABLE default.trino_ck ( id int NOT NULL, birthday DATE NOT NULL, name VARCHAR, age BIGINT, logdate DATE NOT NULL ) WITH ( engine = 'MergeTree', order_by = ARRAY['id', 'birthday'], partition_by = ARRAY['toYYYYMM(logdate)'], primary_key = ARRAY['id'], sample_by = 'id' );
The following are supported ClickHouse table properties from https://clickhouse.tech/docs/en/engines/table-engines/mergetree-family/mergetree/
Name and parameters of the engine.
Array of columns or expressions to concatenate to create the sorting key. Required if
Array of columns or expressions to use as nested partition keys. Optional.
Array of columns or expressions to concatenate to create the primary key. Optional.
An expression to use for sampling. Optional.
Currently the connector only supports
MergeTree table engines
in create table statement.
ReplicatedMergeTree engine is not yet supported.
The connector supports pushdown for a number of operations:
Aggregate pushdown for the following functions:
The connector provides read and write access to data and metadata in a ClickHouse catalog. In addition to the globally available and read operation statements, the connector supports the following features: