Support chDB as a driver

[ThomAub]

Summary

This is a first proposition for #297. It's currently working for our use case of embedded ClickHouse for unit tests with DBT.

It would be great to have some feedback in the direction of this feature implementation !
We would also be interested in how should we add Unit and integration tests or even a tutorial ?

Checklist

Delete items not relevant to your PR:

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

[CLAassistant]

All committers have signed the CLA.

[ThomAub]

also tagging @auxten if you have insight on the chDB part

[auxten]

It looks great. I'm here for any issue or question :)

[ThomAub]

This should be in dbt target provided folder

[ThomAub]

Maybe more granular and able to load single file or glob expression

[auxten]

@ThomAub There are some lint issues to fix, and we also need unit and integration tests.

You can "Allow edits from maintainers."

[BentsiLeviav]

Hi folks,

Thank you for your contribution!

Before reviewing your PR, please add the following:

• A short description with a link to this PR in the changelog (please keep the current format we have in the Changelog file).
• As this feature isn't minor, please add tests to cover the added functionality and documentation to the readme file.

Looking forward to reviewing this!

[auxten]

@ThomAub In the chdb v2.2.0b0, the chdb.dbapi is totally refactored. The API and behavior suppose to be not changed.
The good parts are:

• Stateful Query with long live clickhouse engine instance bind with connection
• Python DB-API reimplemented with new API. Both persist and memory engine supported
• ClickHouse memory engine support
• Some performance improvement (~43%)

[arun11299]

I am eagerly waiting for this so that I can use chDB instead of duckdb for doing local transformations (WIP). Our warehouse is clickhouse, so it would make a lot of sense for us to have a compatible SQL for the local processing as well.

@ThomAub Thanks for the great work. When do you think it would be generally available and maybe with some helpful doc or blog post?

[ThomAub]

We are actively testing this in house so we will soon make it a proper PR with documentation before end of year

[arun11299]

@ThomAub Can you please update us on the PR state ? Is there any more work required to get this merged ?

[ThomAub]

Hello @arun11299 We are facing some issues with using CHDB for testing purposes. We have a Clickhouse cluster, and CHDB is not working well for distributed or replicated tables.
Do you use Dictionaries or Replicated tables ?

[auxten]

@ThomAub Can you describe in detail the problem you have? And which version of chDB you are using, for the scenario of dbt I really recommend chDB v3.0.0

[arunmu-nx]

@ThomAub Maybe a dumb question, but why ChDb needs to worry about replicated merge tables ? Isn't it just embedded and hence single node?

Anyways, in my use case, I want to use ChDb for doing data pipeline implementation and testing in dev environment which is replaced by clickhouse cloud in production.