wiedld commented on code in PR #14907:
URL: https://github.com/apache/datafusion/pull/14907#discussion_r1974080657


##########
datafusion/physical-optimizer/src/enforce_sorting/mod.rs:
##########
@@ -316,25 +369,43 @@ fn replace_with_partial_sort(
 /// are transformed into
 /// ```text
 ///      "SortPreservingMergeExec: \[a@0 ASC\]",
-///      "  ...nodes..."
-///      "    SortExec: expr=\[a@0 ASC\]",
+///      "  SortExec: expr=\[a@0 ASC\]",
+///      "    ...nodes..."
+///      "      RepartitionExec: partitioning=RoundRobinBatch(8), 
input_partitions=1",
+/// ```
+/// by following connections from [`CoalescePartitionsExec`]s to [`SortExec`]s.
+/// By performing sorting in parallel, we can increase performance in some 
scenarios.
+///
+/// This requires that there are no nodes between the [`SortExec`] and 
[`CoalescePartitionsExec`]
+/// which require single partitioning. Do not parallelize when the following 
scenario occurs:
+/// ```text
+///      "SortExec: expr=\[a@0 ASC\]",
+///      "  ...nodes requiring single partitioning..."
+///      "    CoalescePartitionsExec",
 ///      "      RepartitionExec: partitioning=RoundRobinBatch(8), 
input_partitions=1",
 /// ```
 pub fn parallelize_sorts(
     mut requirements: PlanWithCorrespondingCoalescePartitions,
 ) -> Result<Transformed<PlanWithCorrespondingCoalescePartitions>> {
+    requirements = requirements.update_plan_from_children()?;
     update_coalesce_ctx_children(&mut requirements);
+    let coalesce_can_be_removed = requirements.children.iter().any(|child| 
child.data);

Review Comment:
   I switched it to be docs only: 
https://github.com/apache/datafusion/pull/14907#issuecomment-2688656333
   Then if I move forward with another refactoring attempt, I'll first make an 
issue justify the refactor.



##########
datafusion/physical-optimizer/src/enforce_sorting/mod.rs:
##########
@@ -316,25 +369,43 @@ fn replace_with_partial_sort(
 /// are transformed into
 /// ```text
 ///      "SortPreservingMergeExec: \[a@0 ASC\]",
-///      "  ...nodes..."
-///      "    SortExec: expr=\[a@0 ASC\]",
+///      "  SortExec: expr=\[a@0 ASC\]",
+///      "    ...nodes..."
+///      "      RepartitionExec: partitioning=RoundRobinBatch(8), 
input_partitions=1",
+/// ```
+/// by following connections from [`CoalescePartitionsExec`]s to [`SortExec`]s.
+/// By performing sorting in parallel, we can increase performance in some 
scenarios.
+///
+/// This requires that there are no nodes between the [`SortExec`] and 
[`CoalescePartitionsExec`]
+/// which require single partitioning. Do not parallelize when the following 
scenario occurs:
+/// ```text
+///      "SortExec: expr=\[a@0 ASC\]",
+///      "  ...nodes requiring single partitioning..."
+///      "    CoalescePartitionsExec",
 ///      "      RepartitionExec: partitioning=RoundRobinBatch(8), 
input_partitions=1",
 /// ```
 pub fn parallelize_sorts(
     mut requirements: PlanWithCorrespondingCoalescePartitions,
 ) -> Result<Transformed<PlanWithCorrespondingCoalescePartitions>> {
+    requirements = requirements.update_plan_from_children()?;
     update_coalesce_ctx_children(&mut requirements);
+    let coalesce_can_be_removed = requirements.children.iter().any(|child| 
child.data);

Review Comment:
   I switched it to be docs only: 
https://github.com/apache/datafusion/pull/14907#issuecomment-2688656333
   Then if I move forward with another refactoring attempt, I'll first make an 
issue to justify the refactor.



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