[MINOR]: Add getter methods to first and last value (#8555)

datafusion/physical-expr/src/aggregate/first_last.rs

@@ -61,6 +61,31 @@ impl FirstValue {
             ordering_req,
         }
     }
+
+    /// Returns the name of the aggregate expression.
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// Returns the input data type of the aggregate expression.
+    pub fn input_data_type(&self) -> &DataType {
+        &self.input_data_type
+    }
+
+    /// Returns the data types of the order-by columns.
+    pub fn order_by_data_types(&self) -> &Vec<DataType> {
+        &self.order_by_data_types
+    }
+
+    /// Returns the expression associated with the aggregate function.
+    pub fn expr(&self) -> &Arc<dyn PhysicalExpr> {
+        &self.expr
+    }
+
+    /// Returns the lexical ordering requirements of the aggregate expression.
+    pub fn ordering_req(&self) -> &LexOrdering {
+        &self.ordering_req
+    }
 }
 
 impl AggregateExpr for FirstValue {
@@ -285,6 +310,31 @@ impl LastValue {
             ordering_req,
         }
     }
+
+    /// Returns the name of the aggregate expression.
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// Returns the input data type of the aggregate expression.
+    pub fn input_data_type(&self) -> &DataType {
+        &self.input_data_type
+    }
+
+    /// Returns the data types of the order-by columns.
+    pub fn order_by_data_types(&self) -> &Vec<DataType> {
+        &self.order_by_data_types
+    }
+
+    /// Returns the expression associated with the aggregate function.
+    pub fn expr(&self) -> &Arc<dyn PhysicalExpr> {
+        &self.expr
+    }
+
+    /// Returns the lexical ordering requirements of the aggregate expression.
+    pub fn ordering_req(&self) -> &LexOrdering {
+        &self.ordering_req
+    }
 }
 
 impl AggregateExpr for LastValue {