Add support for Snowflake `at timestamp` Time Travel in TableSegment

[alex-mirkin]

Is your feature request related to a problem? Please describe.

When comparing tables across databases that are continuously updated, we need the ability to “freeze” tables at a specific point in time to ensure accurate comparisons. In some cases, we can use the where, min_update, and max_update parameters to achieve a similar result, but there are cases when this is not possible - for example, when there is no updated_at column that tracks the last update date in the table.

Describe the solution you'd like

Snowflake offers a Time Travel feature that allows viewing a table as it existed at a specific timestamp. Example:

SELECT *
FROM my_table AT (TIMESTAMP => '2024-09-10 20:52:25'::timestamp);

By combining this with data-freezing methods from other databases (such as the cluster clone feature in AWS Aurora), we can ensure accurate data comparison.

Describe alternatives you've considered

A user-side alternative for Snowflake is to create a view for each table using the Time Travel syntax before running reladeff, then use these views for comparison instead of the original tables.

Additional context The implementation could include a parameter similar to where that restricts the search space. For example, a snowflake_at_timestamp parameter could be introduced, which would accept a timestamp to specify the point in time for the Snowflake Time Travel.

[erezsh]

I think this is a feature that would be relatively easy to add. I think it would only require changes to table_segment.py

Specifically, the table segment class should be modified to also accept an instance of sqeleton.queries.ast_classes.TimeTravel, in place of a TablePath.

Hopefully it won't require any modifications to sqeleton, although perhaps small adjustments would be required.

If you would like to submit a PR for this, I would be happy to guide you in the process. Once we have support for it in the Python API, we can consider if it's worth adding to the CLI too.

[alex-mirkin]

Great, I’ll work on figuring out the necessary changes and submit the initial work. We can then proceed from there.