fix(db): fixes joined model comparison error

[whitdog47]

In our current implementation, we encountered an error when attempting to join models within our query construction logic. The error message indicated:

Mapped instance expected for relationship comparison to object. Classes, queries and other SQL elements are not accepted in this context; for comparison with a subquery, use Case.assignee.has(**criteria).

This issue arose because our logic was attempting to track joined models using InstrumentedAttribute objects, which led to incorrect comparisons based on object identity rather than logical identity.

Changes Made:

1. Tracking Models Directly:

   • Modified the logic to track the actual model or table objects instead of InstrumentedAttribute objects. This is done by using the parent attribute when available, and defaulting to the joined_model itself when parent is not present. This ensures that we are consistently tracking the logical entities being joined, regardless of whether they are accessed via ORM attributes or directly as tables.

2. Avoiding Duplicate Joins:

   • Implemented a check to determine whether a model or table has already been joined. This is achieved by maintaining a list of joined models or tables (joined_models) and checking for membership before appending new joins. This prevents redundant joins and helps maintain query efficiency.

[Copilot]

Pull Request Overview

This PR fixes issues with tracking joined models in query construction by unifying model identity and preventing redundant joins.

• Tracks the actual model/table via parent or itself to ensure consistent identity.
• Checks and skips already-joined entities to avoid duplicate joins.

Comments suppressed due to low confidence (2)

src/dispatch/database/service.py:489

• There’s no test coverage for the new deduplication logic. Add tests that verify both standard and alias-based joins are correctly added or skipped.

query = query.join(joined_model, isouter=is_outer)

src/dispatch/database/service.py:487

• [nitpick] The variable name model_or_table is generic. Consider renaming to join_target or entity_key to more clearly express its role in deduplication.

model_or_table = getattr(joined_model, "parent", joined_model)