Rich-T-kid commented on code in PR #26159:
URL: https://github.com/apache/datafusion/pull/26159#discussion_r4235780541
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datafusion/common/src/hash_utils.rs:
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@@ -519,6 +517,138 @@ fn hash_generic_byte_view_array<T: ByteViewType>(
}
}
+/// Dense-path unroll width; 8 lanes keep the gather pipeline full on
ARM64/x86.
+#[cfg(not(feature = "force_hash_collisions"))]
+const DICT_SCATTER_LANES: usize = 8;
+
+/// Fold `dict_hash` into `prev` when `MULTI_COL`, else
+/// overwrite with `dict_hash`.
+#[cfg(not(feature = "force_hash_collisions"))]
+#[inline(always)]
+fn maybe_combine_dict_hash<const MULTI_COL: bool>(prev: u64, dict_hash: u64)
-> u64 {
+ if MULTI_COL {
+ combine_hashes(dict_hash, prev)
+ } else {
+ dict_hash
+ }
+}
+
+/// Scatter precomputed dict-value hashes into every key position with no
+/// null checks, 8-way unrolled.
+///
+/// The 8-wide unroll is for performance, splitting the loop into
Review Comment:
good idea to split this up
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