Re: [PR] Add alias check to optimize projections merge [arrow-datafusion]

["jackwener (via GitHub)" <gi...@apache.org>]

jackwener commented on code in PR #8438:
URL: https://github.com/apache/arrow-datafusion/pull/8438#discussion_r1418253641


##########
datafusion/optimizer/src/optimize_projections.rs:
##########
@@ -405,9 +405,25 @@ fn merge_consecutive_projections(proj: &Projection) -> Result<Option<Projection>
         .iter()
         .map(|expr| rewrite_expr(expr, prev_projection))
         .collect::<Result<Option<Vec<_>>>>()?;
-    new_exprs
-        .map(|exprs| Projection::try_new(exprs, prev_projection.input.clone()))
-        .transpose()
+    if let Some(new_exprs) = new_exprs {
+        let new_exprs = new_exprs
+            .into_iter()
+            .zip(proj.expr.iter())
+            .map(|(new_expr, old_expr)| {
+                let new_name = new_expr.name_for_alias()?;
+                let old_name = old_expr.name_for_alias()?;
+                Ok(if new_name != old_name {
+                    // Make sure name is preserved after merging
+                    new_expr.alias(old_name)
+                } else {
+                    new_expr
+                })

Review Comment:
   ```suggestion
                   new_expr.alias_if_changed(old_expr.name_for_alias()?)
   ```



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