fix overflow hash join; did not matter in release

polars/polars-core/src/frame/hash_join/mod.rs

@@ -1825,7 +1825,6 @@ mod test {
 
     #[test]
     #[cfg_attr(miri, ignore)]
-    #[cfg(feature = "dtype-u64")]
     fn test_join_floats() -> Result<()> {
         let df_a = df! {
             "a" => &[1.0, 2.0, 1.0, 1.0],
@@ -1869,4 +1868,20 @@ mod test {
         );
         Ok(())
     }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_join_nulls() -> Result<()> {
+        let a = df![
+            "a" => [Some(1), None, None]
+        ]?;
+        let b = df![
+            "a" => [Some(1), None, None, None, None]
+        ]?;
+
+        let out = a.inner_join(&b, "a", "a")?;
+
+        assert_eq!(out.shape(), (9, 1));
+        Ok(())
+    }
 }

polars/polars-core/src/vector_hasher.rs

@@ -248,15 +248,15 @@ impl AsU64 for Option<u32> {
     fn as_u64(self) -> u64 {
         match self {
             Some(v) => v as u64,
-            // just a number
-            None => u64::MAX,
+            // just a number safe from overflow
+            None => u64::MAX >> 2,
         }
     }
 }
 
 impl AsU64 for Option<u64> {
     fn as_u64(self) -> u64 {
-        self.unwrap_or(u64::MAX)
+        self.unwrap_or(u64::MAX >> 2)
     }
 }