.. Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

.. http://www.apache.org/licenses/LICENSE-2.0

.. Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

.. _howto/operator:ClickHouseOperator:

SQLExecuteQueryOperator for ClickHouse

Use the :class:~airflow.providers.common.sql.operators.sql.SQLExecuteQueryOperator to execute SQL commands in a ClickHouse <https://clickhouse.com/>__ database.

Because :class:~airflow.providers.clickhousedb.hooks.clickhouse.ClickHouseHook extends :class:~airflow.providers.common.sql.hooks.sql.DbApiHook, no dedicated ClickHouse operator is needed — the generic SQLExecuteQueryOperator handles DDL, DML, and analytical queries.

Using the Operator ^^^^^^^^^^^^^^^^^^

Set the conn_id argument to the ID of a :ref:ClickHouse connection <howto/connection:clickhouse>.

.. list-table:: ClickHouse Airflow Connection Metadata :widths: 25 25 :header-rows: 1

• • Parameter
  • Input
• • Host: string
  • ClickHouse server hostname
• • Port: integer
  • HTTP port (default: 8123, TLS: 8443)
• • Login: string
  • ClickHouse username (default: default)
• • Password: string
  • ClickHouse user password
• • Database (Schema): string
  • Default database (default: default)
• • Extra: JSON dict
  • secure, verify, connect_timeout, send_receive_timeout, compress, client_name

An example usage of the SQLExecuteQueryOperator to connect to ClickHouse:

.. exampleinclude:: /../../clickhousedb/tests/system/clickhouse/example_clickhouse.py :language: python :start-after: [START howto_operator_clickhouse] :end-before: [END howto_operator_clickhouse] :dedent: 4

Querying Data ^^^^^^^^^^^^^

Query results are fetched with the default handler (fetch_all_handler):

.. exampleinclude:: /../../clickhousedb/tests/system/clickhouse/example_clickhouse.py :language: python :start-after: [START howto_operator_clickhouse_query] :end-before: [END howto_operator_clickhouse_query] :dedent: 4

To return something other than the full result set, pass a custom handler. For example, fetch_one_handler to fetch only the first row.

.. note::

``session_settings`` passed to :class:`~airflow.providers.clickhousedb.hooks.clickhouse.ClickHouseHook`
directly (via ``hook_params``) take precedence over any ``session_settings`` defined in the
connection's ``extra`` JSON field. Conflicting keys are resolved in favor of the constructor argument.