Update schema_migration_tools.md

[d-ganchar]

Summary

Python tools, link to Thedus

[CLAassistant]

All committers have signed the CLA.

[SpencerTorres]

Thanks for making a migration tool for ClickHouse!

I'm not sure the official policy for adding new tools to this list, but I would like to see some more documentation on how to use this project. It looks like the first commit/release was only a couple days ago. For the sake of security and QA, maybe this should wait a bit until the project matures.

I see you've also contributed to Houseplant. What is the difference between these two tools? I see Houseplant is also new (about a month old), but seems to have some decent documentation available as well as some downloads/stars showing people using/contributing to it.

Could you provide some more info about your project? Thanks!

[d-ganchar]

Thanks for making a migration tool for ClickHouse!

I'm not sure the official policy for adding new tools to this list, but I would like to see some more documentation on how to use this project. It looks like the first commit/release was only a couple days ago. For the sake of security and QA, maybe this should wait a bit until the project matures.

I see you've also contributed to Houseplant. What is the difference between these two tools? I see Houseplant is also new (about a month old), but seems to have some decent documentation available as well as some downloads/stars showing people using/contributing to it.

Could you provide some more info about your project? Thanks!

Hey!

Thank you for your response.
The reasons why I created another package:

• Houseplant may have stars and downloads, but if you follow the documentation, it doesn’t work ( 33, 34, 35 )
• Houseplant uses mocks for interface tests. Thedus runs tests on the built and installed package, ensuring that the interface works fine.
• Houseplant uses the YAML format for migrations. This is not always a good solution for writing SQL. Thedus uses Python for executing migrations, which provides more flexibility and capabilities. See demo files.
• Houseplant relies on ReplicatedReplacingMergeTree, FINAL, and OPTIMIZE TABLE to store state. Thedus has no state - it keeps a log of executed migrations and runs.
• Thedus allows you to see if a migration was skipped due to environment settings. With Houseplant, you will see that the migration was executed, but in reality, no changes were made to the database.

To be honest, I wouldn’t add this to the documentation without cli tests verifying logs and database state(using multiple Py versions)
I think this could be really useful for someone. Moreover, I'll use Thedus in production myself when finish with requirements, cluster design and setup.