changes

[SFJohnson24]

This pull request improves the robustness and correctness of the Distinct operation, especially in handling empty datasets and grouped operations. It also adds comprehensive unit tests to cover these scenarios. The main changes are as follows:

Enhanced Handling of Empty Datasets in Grouped Operations

• The Distinct operation now correctly returns an empty grouped result with the appropriate columns when the input dataset is empty or when a filter produces zero rows, instead of failing or returning incorrect results. This is achieved by adding the _build_empty_grouped_result helper method and updating the execution logic to use it as needed. [1] [2] [3]

Improved Reference Column Handling

• The _check_column_exists_in_dataset function and its usage were updated to allow the referenced domain column name to be configurable (defaulting to "RDOMAIN"), increasing flexibility for different dataset schemas. [1] [2] [3]

Bug Fix in Result Expansion

• Fixed a bug in _expand_operation_results_in_grouping to handle the case when an operation column is empty, preventing errors during result expansion.

Testing Improvements

• Added new parameterized unit tests to verify correct behavior of the Distinct operation for both empty datasets and filtered grouped results that yield zero rows, for both Pandas and Dask backends.

Test Infrastructure

• Added missing pandas import in the test file to support new test cases.

PR addresses attached issue. I updated SCheduleDecisionInstance in the test data for core-000804 to test;

parent_entity,parent_id,parent_rel,rel_type,id,name,description,label,defaultConditionId,epochId,timelineId,timelineExitId,instanceType,conditionAssignments
ScheduleTimeline,ScheduleTimeline_4,instances,definition,ScheduledDecisionInstance_1,Meet requirements for WK6 or end,,,ScheduledActivityInstance_27,,,,ScheduledDecisionInstance,true
ScheduleTimeline,ScheduleTimeline_4,entryId,reference,ScheduledDecisionInstance_1,Meet requirements for WK6 or end,,,ScheduledActivityInstance_27,,,,ScheduledDecisionInstance,true

this produces a scheduledesicioninstance with no timing instance

worth noting: conditionAssignments is cast as a bool and the current data in the repo is not able to be cast as such since it is a string

I also tested CORE-000712 given it's distinct-specific operation logic

[pendingintent]

Looks good and all tests passing.