Minor: use Expr::alias in a few places to make the code more concise (#8097)

Author: alamb

datafusion/optimizer/src/decorrelate.rs

@@ -227,10 +227,9 @@ impl TreeNodeRewriter for PullUpCorrelatedExpr {
                     )?;
                     if !expr_result_map_for_count_bug.is_empty() {
                         // has count bug
-                        let un_matched_row = Expr::Alias(Alias::new(
-                            Expr::Literal(ScalarValue::Boolean(Some(true))),
-                            UN_MATCHED_ROW_INDICATOR.to_string(),
-                        ));
+                        let un_matched_row =
+                            Expr::Literal(ScalarValue::Boolean(Some(true)))
+                                .alias(UN_MATCHED_ROW_INDICATOR);
                         // add the unmatched rows indicator to the Aggregation's group expressions
                         missing_exprs.push(un_matched_row);
                     }

datafusion/optimizer/src/single_distinct_to_groupby.rs

@@ -25,7 +25,7 @@ use crate::{OptimizerConfig, OptimizerRule};
 use datafusion_common::Result;
 use datafusion_expr::{
     col,
-    expr::{AggregateFunction, Alias},
+    expr::AggregateFunction,
     logical_plan::{Aggregate, LogicalPlan},
     Expr,
 };
@@ -168,16 +168,14 @@ impl OptimizerRule for SingleDistinctToGroupBy {
                                         args[0].clone().alias(SINGLE_DISTINCT_ALIAS),
                                     );
                                 }
-                                Ok(Expr::Alias(Alias::new(
-                                    Expr::AggregateFunction(AggregateFunction::new(
-                                        fun.clone(),
-                                        vec![col(SINGLE_DISTINCT_ALIAS)],
-                                        false, // intentional to remove distinct here
-                                        filter.clone(),
-                                        order_by.clone(),
-                                    )),
-                                    aggr_expr.display_name()?,
-                                )))
+                                Ok(Expr::AggregateFunction(AggregateFunction::new(
+                                    fun.clone(),
+                                    vec![col(SINGLE_DISTINCT_ALIAS)],
+                                    false, // intentional to remove distinct here
+                                    filter.clone(),
+                                    order_by.clone(),
+                                ))
+                                .alias(aggr_expr.display_name()?))
                             }
                             _ => Ok(aggr_expr.clone()),
                         })

datafusion/sql/src/select.rs

@@ -373,7 +373,7 @@ impl<'a, S: ContextProvider> SqlToRel<'a, S> {
                     &[&[plan.schema()]],
                     &plan.using_columns()?,
                 )?;
-                let expr = Expr::Alias(Alias::new(col, self.normalizer.normalize(alias)));
+                let expr = col.alias(self.normalizer.normalize(alias));
                 Ok(vec![expr])
             }
             SelectItem::Wildcard(options) => {