korowa opened a new pull request, #8721:
URL: https://github.com/apache/arrow-datafusion/pull/8721
## Which issue does this PR close?
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Part of #5472.
## Rationale for this change
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Why are you proposing this change? If this is already explained clearly in
the issue then this section is not needed.
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Improvement of `DistinctCountAccumulator` performance for groups case (when
it actually executed, and not replaced by double aggregation) -- the main idea
was to avoid `ScalarValue` wrappers for all update/merge operations. In
addition -- implementation of `GroupsAccumulator` trait turned out to be faster
than regular `Accumulator` with HashSet of primitives (still is going to be one
of the possible follow ups -- for "single group" cases).
## What changes are included in this PR?
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- `Hashable` newtype for arrow primitives moved to utils module -- required
to use `ArrowPrimitiveType::Native` types as hashmap/hashset keys
- `DistinctCountGroupsAccumulator` for primitive arrow types -- internal
state stores HashSet of unique values for each `group_index` in a single
vector. Accumulator doesn't perform null tracking -- on updates/merges internal
state is resized with empty HashSets, and accumulator evaluation returns
lengths of corresponding HashSets on `evaluate` calls.
## Are these changes tested?
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Unit tests for `GroupsAccumulator` methods -- update / state / evaluate /
merge for all primitive types + tests for filtered accumulator updates / merges.
## Are there any user-facing changes?
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No
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