Fix projection name with DataFrame::with_column and window functions

datafusion/core/src/dataframe/mod.rs

@@ -1441,21 +1441,27 @@ impl DataFrame {
     /// ```
     pub fn with_column(self, name: &str, expr: Expr) -> Result<DataFrame> {
         let window_func_exprs = find_window_exprs(&[expr.clone()]);
-        let plan = if window_func_exprs.is_empty() {
-            self.plan
+
+        let (plan, mut col_exists, window_func) = if window_func_exprs.is_empty() {
+            (self.plan, false, false)
         } else {
-            LogicalPlanBuilder::window_plan(self.plan, window_func_exprs)?
+            (
+                LogicalPlanBuilder::window_plan(self.plan, window_func_exprs)?,
+                true,
+                true,
+            )
         };
 
         let new_column = expr.alias(name);
-        let mut col_exists = false;
         let mut fields: Vec<Expr> = plan
             .schema()
             .iter()
             .map(|(qualifier, field)| {
                 if field.name() == name {
                     col_exists = true;
                     new_column.clone()
+                } else if window_func && qualifier.is_none() {
+                    col(Column::from((qualifier, field))).alias(name)
                 } else {
                     col(Column::from((qualifier, field)))
                 }
@@ -1704,6 +1710,7 @@ mod tests {
     use datafusion_common::{Constraint, Constraints, ScalarValue};
     use datafusion_common_runtime::SpawnedTask;
     use datafusion_expr::expr::WindowFunction;
+    use datafusion_expr::window_function::row_number;
     use datafusion_expr::{
         cast, create_udf, expr, lit, BuiltInWindowFunction, ExprFunctionExt,
         ScalarFunctionImplementation, Volatility, WindowFrame, WindowFrameBound,
@@ -2956,6 +2963,35 @@ mod tests {
         Ok(())
     }
 
+    // Test issue: https://github.com/apache/datafusion/issues/11982
+    // Window function was creating unwanted projection when using with_column() method.
+    #[tokio::test]
+    async fn test_window_function_with_column() -> Result<()> {
+        let df = test_table().await?.select_columns(&["c1", "c2", "c3"])?;
+        let ctx = SessionContext::new();
+        let df_impl = DataFrame::new(ctx.state(), df.plan.clone());
+        let func = row_number().alias("row_num");
+
+        // Should create an additional column with alias 'r' that has window func results
+        let df = df_impl.with_column("r", func)?.limit(0, Some(2))?;
+        assert_eq!(4, df.schema().fields().len());
+
+        let df_results = df.clone().collect().await?;
+        assert_batches_sorted_eq!(
+            [
+                "+----+----+-----+---+",
+                "| c1 | c2 | c3  | r |",
+                "+----+----+-----+---+",
+                "| c  | 2  | 1   | 1 |",
+                "| d  | 5  | -40 | 2 |",
+                "+----+----+-----+---+",
+            ],
+            &df_results
+        );
+
+        Ok(())
+    }
+
     // Test issue: https://github.com/apache/datafusion/issues/7790
     // The join operation outputs two identical column names, but they belong to different relations.
     #[tokio::test]