ClickHouse connector#

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 to clickhouse.

For example, to access a server as clickhouse, create the file etc/catalog/ Replace the connection properties as appropriate for your setup:

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 etc/catalog

  • Save it with a different name that ends in .properties

For example, if you name the property file, Trino uses the configured connector to create a catalog named sales.

General configuration properties#

The following table describes general configuration properties for the connector:

Property name


Default value


Match schema and table names case insensitively



1 minute


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

0 (disabled caching)


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



Maximum number of objects stored in the metadata cache



Maximum number of statements in a batched execution. Do not change this setting from the default. Non-default values may negatively impact performance.



Enable join pushdown. Equivalent catalog session property is join_pushdown_enabled. Enabling this may negatively impact performance for some queries.


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.

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;


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

Table properties#

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
  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

Property Name

Default Value




Name and parameters of the engine.



Array of columns or expressions to concatenate to create the sorting key. Required if engine is MergeTree.



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 Log and MergeTree table engines in create table statement. ReplicatedMergeTree engine is not yet supported.

Type mapping#

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


Default value


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.



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


The connector supports pushdown for a number of operations:

Aggregate pushdown for the following functions:

SQL support#

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: