EPIC: Complete GroupValuesColumn for Faster Aggregation support #24268

• Follow on to EPIC: complete GroupValuesColumn type coverage (nested types + remaining primitives) #22715 (comment)

Is your feature request related to a problem or challenge?

When running a query like SELECT ... GROUP BY x, y the DataFusion grouping operator computes / stores the group keys using an instance of the GroupValuesColumn trait.

This trait is a column-wise provides type-specific specializations under multi_group_by

If any one of the group by keys does not have a specialization of GroupValuesColumn DataFusion falls back to the general, but slower byte-encoded GroupValuesRows.

The currently supported types are listed in group_column_supported_type:

Definition of Done

This EPIC tracks completing the GroupValuesColumn type coverage so that GroupValuesRows can be removed

Subtasks

• feat: add GroupColumn support for List / Struct / Map / FixedSizeList in multi-column GROUP BY #22682
• Specialize GroupColumn storage for Dictionary and Run-End Encoded group keys #23993
• feat: add generic FallbackGroupColumn so any Arrow type uses GroupValuesColumn (no fallback to GroupValuesRows) #22701
• GROUP BY on a Dictionary column fails at runtime when distinct group count exceeds the key type's capacity #23127

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