tobixdev commented on code in PR #16977:
URL: https://github.com/apache/datafusion/pull/16977#discussion_r2244441946


##########
datafusion/expr/src/udf.rs:
##########
@@ -720,13 +721,15 @@ pub trait ScalarUDFImpl: Debug + Send + Sync {
     /// Similarly to [`Hash`] and [`Eq`], if [`Self::equals`] returns true for 
two UDFs,
     /// their `hash_value`s must be the same.
     ///
-    /// By default, it is consistent with default implementation of 
[`Self::equals`].
+    /// By default, it hashes the type, [`Self::name`], and [`Self::aliases`]. 
[`Self::signature`]
+    /// is not hashed, as usually the signature is implied by the UDF type. 
Recall that UDFs with
+    /// state (and thus possibly changing signature) must override 
[`Self::equals`] and
+    /// [`Self::hash_value`].
     fn hash_value(&self) -> u64 {
-        let hasher = &mut DefaultHasher::new();
+        let hasher = &mut AHasher::default();
         self.as_any().type_id().hash(hasher);
         self.name().hash(hasher);
         self.aliases().hash(hasher);

Review Comment:
   Done, would be interesting if this changes the benchmarks.



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