Rich-T-kid opened a new pull request, #26159:
URL: https://github.com/apache/datafusion/pull/26159
Rework hash_dictionary_scatter so the key-null handling runs in 64-bit
BitChunks instead of per-row Option unwrap, and route all-valid chunks plus the
no-null-keys fast path through an 8-way unrolled dense scatter that keeps the
dict gather pipeline full. Mixed chunks use a branchless csel blend
(safe-clamped indices) when dict values are all valid; the rarer
HAS_NULL_VALUES mixed path falls back to the per-bit scan for correctness.
Benchmarks (datafusion/common/benches/with_hashes.rs, Apple M4 Max):
dictionary_utf8_int32 single, no nulls : 2.91 µs -> 1.83 µs (-37%)
dictionary_utf8_int32 multiple, no nulls: 9.10 µs -> 5.67 µs (-38%)
dictionary_utf8_int32 single, nulls : 7.11 µs -> 2.81 µs (-60%)
dictionary_utf8_int32 multiple, nulls : 20.90 µs -> 8.21 µs (-61%)
Non-dict benchmarks (int64, utf8_view small) stay within noise.
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