[Rust] [DataFusion] HashAggregate walks map many times building final batch #25735
Description
The current HashAggregate implementation iterates over the final hash map once for each grouping expression and once for each aggregate expression. This is inefficient and possibly dangerous depending on the ordering gaurantees made by the hash map implementation.
Reporter: Andy Grove / @andygrove
Assignee: Andy Grove / @andygrove
PRs and other links:
Note: This issue was originally created as ARROW-9679. Please see the migration documentation for further details.