Github user dongjoon-hyun commented on a diff in the pull request:
https://github.com/apache/spark/pull/13765#discussion_r68794253
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -537,12 +537,19 @@ object CollapseProject extends Rule[LogicalPlan] {
}
/**
- * Combines adjacent [[Repartition]] operators by keeping only the last
one.
+ * Combines adjacent [[Repartition]] and [[RepartitionByExpression]]
operator combinations
+ * by keeping only the one.
*/
object CollapseRepartition extends Rule[LogicalPlan] {
def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
case Repartition(numPartitions, shuffle, Repartition(_, _, child)) =>
Repartition(numPartitions, shuffle, child)
+ case Repartition(numPartitions, _, r: RepartitionByExpression) =>
+ r.copy(numPartitions = Some(numPartitions))
+ case RepartitionByExpression(exprs, Repartition(_, _, child),
numPartitions) =>
+ RepartitionByExpression(exprs, child, numPartitions)
+ case RepartitionByExpression(exprs, RepartitionByExpression(_, child,
_), numPartitions) =>
+ RepartitionByExpression(exprs, child, numPartitions)
--- End diff --
Actually, it aims the followings SQLs. It's a kind of query organizing
clause in SQL, e.g., ORDER BY, CLUSTER BY, DISTRIBUTE BY, SORT BY, LIMIT.
Actually, the risk what you concern is about `exprs` depencency, right?
**Before**
```scala
scala> sql("(select * from values (1,'a'),(2,'b') T(a,b) distribute by a)
distribute by b").explain
== Physical Plan ==
Exchange hashpartitioning(b#3, 200)
+- Exchange hashpartitioning(a#2, 200)
+- LocalTableScan [a#2, b#3]
```
**After**
```scala
scala> sql("(select * from values (1,'a'),(2,'b') T(a,b) distribute by a)
distribute by b").explain
== Physical Plan ==
Exchange hashpartitioning(b#1, 200)
+- LocalTableScan [a#0, b#1]
```
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