Gabriel39 commented on code in PR #13536:
URL: https://github.com/apache/doris/pull/13536#discussion_r1001333560


##########
be/src/util/hash_util.hpp:
##########
@@ -45,11 +45,19 @@ namespace doris {
 // Utility class to compute hash values.
 class HashUtil {
 public:
+    // like hash_combine but without hash
+    static inline uint32_t direct_combine(uint32_t x, uint32_t y) {
+        return x + 0x9e3779b9 + (y << 6) + (y >> 2);
+    }
+
     template <typename T>
     static uint32_t fixed_len_to_uint32(T value) {
         if constexpr (sizeof(T) <= sizeof(uint32_t)) {
             return value;
+        } else if constexpr (sizeof(T) == sizeof(uint64_t)) {
+            return direct_combine(((uint64_t)value << 32) >> 32, 
(uint64_t)value >> 32);

Review Comment:
   using `value & (((uint32_t) 0) - 1)` to extract low bits is more efficient?



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