title: 'ClickHouse Data Connector' sidebar_label: 'ClickHouse Data Connector' description: 'ClickHouse Data Connector Documentation'

ClickHouse is a fast, open-source columnar database management system designed for online analytical processing (OLAP) and real-time analytics. This connector enables federated SQL queries from a ClickHouse server.

datasets:
  - from: clickhouse:my.dataset
    name: my_dataset

datasets:
  - from: clickhouse:my.dataset
    name: my_dataset

Configuration

from

The from field for the ClickHouse connector takes the form of from:db.dataset where db.dataset is the path to the Dataset within ClickHouse. In the example above it would be my.dataset.

The clickhouse_db parameter is required when not using clickhouse_connection_string. When using a connection string without a database path, it defaults to the default database.

:::info Unquoted identifiers are normalized to lowercase. To reference a table or database with mixed-case characters, wrap each case-sensitive part in double quotes: clickhouse:my_db."MixedCaseTable". See Identifier Case Sensitivity (opens in a new tab). :::

name

The dataset name. This will be used as the table name within Spice.

datasets:
  - from: clickhouse:my.dataset
    name: cool_dataset

datasets:
  - from: clickhouse:my.dataset
    name: cool_dataset

SELECT COUNT(*) FROM cool_dataset;

SELECT COUNT(*) FROM cool_dataset;

+----------+
| count(*) |
+----------+
| 6001215  |
+----------+

+----------+
| count(*) |
+----------+
| 6001215  |
+----------+

The dataset name cannot be a reserved keyword (opens in a new tab) or any of the following keywords that are reserved by ClickHouse:

• PREWHERE
• SETTINGS
• FORMAT

params

The ClickHouse data connector can be configured by providing the following params:

Types

The table below shows the ClickHouse data types supported, along with the type mapping to Apache Arrow types in Spice.

DateTime64(P) maps to the coarsest Arrow timestamp unit that holds its precision exactly. Timestamps have no Arrow timezone: values are UTC instants, including for columns declared with a timezone such as DateTime('UTC') or DateTime64(3, 'Asia/Tokyo'). Arrow nanosecond timestamps end at 2262-04-11, so reading a DateTime64(7) or DateTime64(8) value after that date returns an error that names the value rather than a truncated timestamp.

A named Tuple element keeps its name as the Struct field name. An unnamed element is named by its 1-based position (1, 2, and so on), matching how ClickHouse addresses tuple elements.

LowCardinality is supported as a top-level column type, including LowCardinality(Nullable(T)). A LowCardinality type nested inside an Array, Map, or Tuple, such as Array(LowCardinality(String)), is not supported and returns an Unsupported Clickhouse type error. SimpleAggregateFunction columns are not supported.

Examples

Connecting to localhost

datasets:
  - from: clickhouse:my.dataset
    name: my_dataset
    params:
      clickhouse_host: localhost
      clickhouse_tcp_port: 9000
      clickhouse_db: my_database
      clickhouse_user: my_user
      clickhouse_pass: ${secrets:my_clickhouse_pass}
      connection_timeout: 10000
      clickhouse_secure: false

datasets:
  - from: clickhouse:my.dataset
    name: my_dataset
    params:
      clickhouse_host: localhost
      clickhouse_tcp_port: 9000
      clickhouse_db: my_database
      clickhouse_user: my_user
      clickhouse_pass: ${secrets:my_clickhouse_pass}
      connection_timeout: 10000
      clickhouse_secure: false

Specifying a connection timeout

datasets:
  - from: clickhouse:my.dataset
    name: my_dataset
    params:
      clickhouse_connection_string: tcp://my_user:${secrets:my_clickhouse_pass}@localhost:9000/my_database
      connection_timeout: 10000
      clickhouse_secure: true

datasets:
  - from: clickhouse:my.dataset
    name: my_dataset
    params:
      clickhouse_connection_string: tcp://my_user:${secrets:my_clickhouse_pass}@localhost:9000/my_database
      connection_timeout: 10000
      clickhouse_secure: true

Using a connection string

datasets:
  - from: clickhouse:my.dataset
    name: my_dataset
    params:
      clickhouse_connection_string: tcp://my_user:${secrets:my_clickhouse_pass}@localhost:9000/my_database?connection_timeout=10000ms&secure=true

datasets:
  - from: clickhouse:my.dataset
    name: my_dataset
    params:
      clickhouse_connection_string: tcp://my_user:${secrets:my_clickhouse_pass}@localhost:9000/my_database?connection_timeout=10000ms&secure=true

Secrets

Spice integrates with multiple secret stores to help manage sensitive data securely. For detailed information on supported secret stores, refer to the secret stores documentation (opens in a new tab). Additionally, learn how to use referenced secrets in component parameters by visiting the using referenced secrets guide (opens in a new tab).

Cookbook

• A cookbook recipe to configure ClickHouse as data connector in Spice. Clickhouse Data Connector (opens in a new tab)