fix(datatypes): correct ConstantVector rhs comparison in vector equality (#7866)

* fix(datatypes): compare ConstantVector rhs inner in vector equality

When either operand is a ConstantVector, the recursive equal() call must
compare lhs.inner() against rhs.inner(). The second argument incorrectly
used lhs twice, breaking equality when only the rhs was constant.

Signed-off-by: Weixie Cui <cuiweixie@gmail.com>

* fix: review

Signed-off-by: Weixie Cui <cuiweixie@gmail.com>

---------

Signed-off-by: Weixie Cui <cuiweixie@gmail.com>

src/datatypes/src/vectors/eq.rs

@@ -67,7 +67,7 @@ fn equal(lhs: &dyn Vector, rhs: &dyn Vector) -> bool {
                 .downcast_ref::<ConstantVector>()
                 .unwrap()
                 .inner(),
-            &**lhs
+            &**rhs
                 .as_any()
                 .downcast_ref::<ConstantVector>()
                 .unwrap()
@@ -259,6 +259,22 @@ mod tests {
         ])));
     }
 
+    // Regression: second arm must downcast `rhs` (was `lhs`), or same-length ConstantVectors
+    // with different inners compare equal.
+    #[test]
+    fn test_constant_vector_eq_compares_both_inners() {
+        assert_vector_ref_ne(
+            Arc::new(ConstantVector::new(
+                Arc::new(BooleanVector::from(vec![true])),
+                5,
+            )),
+            Arc::new(ConstantVector::new(
+                Arc::new(BooleanVector::from(vec![false])),
+                5,
+            )),
+        );
+    }
+
     #[test]
     fn test_vector_ne() {
         assert_vector_ref_ne(