Store: add persistent dependency registry and notify hook

[sejalpunwatkar]

Summary

This PR introduces a persistent dependency mechanism for AttributeFunctions within the Store, enabling a foundation for observer-style updates across sessions.

What’s implemented

• Added a dependency registry stored inside the existing SqliteDict using a reserved key
• Implemented register_dependency(key, dependent_id) to track relationships between AttributeFunctions
• Hooked into Store.put() to trigger notifications for dependent AttributeFunctions
• Ensured registry persistence across Store reloads

Design decisions

• Used a single-store approach (same SqliteDict) for both data and metadata to avoid cross-store consistency issues
• Kept the implementation minimal and non-intrusive, without modifying existing AttributeFunction or observer semantics
• Did not assume a fixed signature for update() methods to maintain compatibility with current implementations

Tests

• Added test to verify dependency registration and persistence
• Added test to ensure notification hook executes without breaking existing behavior

Scope

This PR focuses on establishing a persistent observer foundation. It does not enforce or redefine observer/update behavior, leaving room for future API design and refinement.

[jensdittrich]

so this is basically a dependency mechanism independent from observable/observers, this means it is up to the user to additonally register those dependencies? That sounds error-prone to me.

In general, this unit test is very short.

[jensdittrich]

please make sure to follow the contribution guideline

[jensdittrich]

what is the purpose of this string?

[jensdittrich]

You are suppressing a possible exception here? Why?

[sejalpunwatkar]

Hi @jensdittrich ,
Thank you for the feedback. I have updated the code to address your concerns:

• Automated Notifications: I moved the notification logic into Store.put(). This means dependencies are updated automatically when an object is saved, so the user doesn't have to do it manually.
• Purpose of the String: The dependency_registry string is used as a private key to save the dependency map inside the SqliteDict. This allows the relationships to be persistent and survive a store restart.
• Exception Handling: I removed the try/except block. The test now uses a proper mock function that handles the expected arguments, so it no longer suppresses errors.
• Improved Testing: I expanded the unit test to verify the full cycle: registering a dependency, triggering an automatic update, and checking that the data persists after closing and reopening the store.
• Guidelines: I updated the variable names to use uuid.UUID and added docstrings to match the project's contribution guidelines.
  Please let me know if you have further suggestions.

[sejalpunwatkar]

@jensdittrich I've updated the code to address your feedback, including the automated notifications and expanded tests. Please take a look whenever you have a moment!
Since you mentioned you're currently focusing on the FQL operators and the query push-down challenge, I’d love to help out there as well. Would you like me to look into the group_by rewrites or start exploring how to improve the where() API for the store?

[jensdittrich]

I am currently returnign from EDBT, I will take a look at your code next week.

[sejalpunwatkar]

Thank you for the update. I hope the conference was successful and look forward to your feedback next week. In the meantime, I’ll continue reviewing the FQL operators and the group_by logic to see where I can best assist with the next steps.