Dandandan commented on code in PR #8721:
URL: https://github.com/apache/arrow-datafusion/pull/8721#discussion_r1440115934
##########
datafusion/physical-expr/src/aggregate/count_distinct.rs:
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@@ -192,20 +285,175 @@ impl Accumulator for DistinctCountAccumulator {
}
}
+struct DistinctCountGroupsAccumulator<T>
+where
+ T: ArrowPrimitiveType + Send,
+{
+ /// Vector for storing unique values sets for each group index
+ unique_values: Vec<HashSet<Hashable<T::Native>>>,
Review Comment:
I hoped we could store this in something like `HashSet<(usize, T::Native)>`,
i.e. we could ammortize the allocations for all the groups instead of creating
a hashset for each group.
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