ClickHouse/clickhouse-connect

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## ClickHouse Connect [![clickhouse-connect on PyPI](https://img.shields.io/pypi/v/clickhouse-connect?label=clickhouse-connect)](https://pypi.org/project/clickhouse-connect/) [![clickhouse-connect-core on PyPI](https://img.shields.io/pypi/v/clickhouse-connect-core?label=clickhouse-connect-core)](https://pypi.org/project/clickhouse-connect-core/) A high performance core database driver for connecting ClickHouse to Python, Pandas, and Superset * Pandas DataFrames (numpy and arrow-backed). Requires pandas 2.0 or later. * Numpy Arrays * PyArrow Tables * Polars DataFrames * Superset Connector * SQLAlchemy Core (select, joins, lightweight deletes; limited feature set) ClickHouse Connect works with both ClickHouse Cloud and self-hosted ClickHouse. You can [start a free Cloud trial](https://console.clickhouse.cloud/signUp?utm_medium=referral&utm_source=github&utm_campaign=readme&utm_content=clickhouse-connect) or [install ClickHouse](https://clickhouse.com/docs/get-started/setup/install) locally. For local development, you can also start ClickHouse with the included [Docker Compose configuration](CONTRIBUTING.md#start-clickhouse-in-docker). ClickHouse Connect uses the ClickHouse HTTP interface for maximum compatibility. An experimental [chDB](https://clickhouse.com/docs/chdb) backend is also available for running queries against an embedded in-process engine with `get_client(interface='chdb')`. Install it with `pip install clickhouse-connect[chdb]`. ### Installation ``` pip install clickhouse-connect ``` ClickHouse Connect requires Python 3.10 or higher. #### Upgrading from 0.x The 1.0 release includes breaking changes. If you are upgrading from a 0.15.x or earlier release, see [MIGRATION.md](MIGRATION.md) for a guide to the changes and their replacements. ### Releases `clickhouse-connect` and the optional `clickhouse-connect-core` Rust binding are versioned independently. The badges above show their latest published PyPI versions. [GitHub Releases](https://github.com/ClickHouse/clickhouse-connect/releases) track `clickhouse-connect`. See the [driver changelog](CHANGELOG.md) and the [core binding changelog](rust/ch-core-py/CHANGELOG.md) for release notes. ### Superset Connectivity ClickHouse Connect is fully integrated with Apache Superset. Previous versions of ClickHouse Connect utilized a dynamically loaded Superset Engine Spec, but as of Superset v2.1.0 the engine spec was incorporated into the main Apache Superset project and removed from clickhouse-connect in v0.6.0. If you have issues connecting to earlier versions of Superset, please use clickhouse-connect v0.5.25. When creating a Superset Data Source, either use the provided connection dialog, or a SqlAlchemy DSN in the form `clickhousedb://{username}:{password}@{host}:{port}`. ### SQLAlchemy Implementation ClickHouse Connect includes a lightweight SQLAlchemy dialect implementation focused on compatibility with **Superset** and **SQLAlchemy Core**. The synchronous dialect supports SQLAlchemy 1.4 and 2.x. SQLAlchemy 1.4 compatibility is maintained because Apache Superset currently requires `sqlalchemy>=1.4,<2`. Use `clickhousedb://` or `clickhousedb+connect://` for synchronous connections. When `clickhouse-sqlalchemy` is also installed, importing our dialect preserves its `clickhouse://` registration. See the [migration guide](clickhouse_connect/cc_sqlalchemy/MIGRATING_FROM_CLICKHOUSE_SQLALCHEMY.md) for URL and schema-option compatibility. Async SQLAlchemy usage is available with SQLAlchemy 2.0.44 and later. Install `clickhouse-connect[sqlalchemy-async]` and use `clickhousedb+async://` with `create_async_engine()`. Results are buffered. Server-side cursors are not supported. Always await the async engine's `dispose()` method during shutdown instead of calling `engine.sync_engine.dispose()`. Supported features include: - Basic query execution via SQLAlchemy Core - `SELECT` queries with `JOIN`s (including ClickHouse-specific strictness, `USING`, and `GLOBAL` modifiers), `ARRAY JOIN` (single and multi-column), `FINAL`, `SAMPLE`, compound selects, and materialized CTEs - `VALUES` table function syntax - Lightweight `DELETE` statements - **Alembic** schema migrations (autogenerate, upgrade/downgrade, ClickHouse engine support) A small number of features require SQLAlchemy 2.x. `Values.cte()` specifically requires SQLAlchemy 2.0.42 or later. Certain literal-rendering behaviors also require SQLAlchemy 2.x. All other dialect features, including those used by Superset, work on both 1.4 and 2.x. Basic ORM usage works for insert-heavy, read-focused workloads: declarative model definitions, `CREATE TABLE`, `session.add()`, `bulk_save_objects()`, and read queries all function correctly. However, full ORM support is not provided. UPDATE compilation, foreign key/relationship reflection, autoincrement/RETURNING, and cascade operations are not implemented. The dialect is best suited for SQLAlchemy Core usage and Superset connectivity. #### Alembic Migrations ClickHouse Connect supports [Alembic](https://alembic.sqlalchemy.org/) for schema migrations, including autogeneration of migration scripts from SQLAlchemy metadata. ClickHouse table engines (`MergeTree`, `ReplacingMergeTree`, etc.) and dictionaries are preserved through the migration lifecycle. Supported operations include create/drop table, add/alter/drop/rename column, type and nullability changes, defaults, comments, and ClickHouse-specific features like `IF EXISTS` guards, column placement with `AFTER`, and operation-level `clickhouse_settings` on column add/alter/drop. To get started, install the Alembic extra: ```bash pip install clickhouse-connect[alembic] ``` For Alembic with the async SQLAlchemy dialect, install `clickhouse-connect[alembic,sqlalchemy-async]`, run `alembic init -t async alembic`, and replace the generated `alembic/env.py` with the checked-in [async Alembic environment](examples/alembic_async/env.py). Keep the generated `script_location = %(here)s/alembic`, or update it if you chose a different migration directory. The example includes the ClickHouse Alembic hooks and options, runs online migrations through `AsyncConnection.run_sync()`, and compiles offline migrations without creating an engine. See the [Alembic worked example](clickhouse_connect/cc_sqlalchemy/alembic/WORKED_EXAMPLE.md) for a full end-to-end walkthrough covering setup, autogeneration, upgrades, downgrades, and manual migration operations. ### Asyncio Support ClickHouse Connect provides native async support using aiohttp. To use the async client, install the optional async dependency: ``` pip install clickhouse-connect[async] ``` Then create a client with `clickhouse_connect.get_async_client()`. See the [run_async example](./examples/run_async.py) for more details. ### Complete Documentation The documentation for ClickHouse Connect has moved to [ClickHouse Docs](https://clickhouse.com/docs/integrations/python)

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