# clickhouse-connect

**Repository Path**: mirrors_ClickHouse/clickhouse-connect

## Basic Information

- **Project Name**: clickhouse-connect
- **Description**: Python driver/sqlalchemy/superset connectors
- **Primary Language**: Unknown
- **License**: Apache-2.0
- **Default Branch**: main
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2022-06-16
- **Last Updated**: 2026-08-01

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

## ClickHouse Connect

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 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.

### 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**. Both SQLAlchemy 1.4 and 2.x are supported. SQLAlchemy 1.4 compatibility is maintained
because Apache Superset currently requires `sqlalchemy>=1.4,<2`.

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`, and `SAMPLE`
- `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()` and certain literal-rendering behaviors.
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]
```

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)