wangyum commented on code in PR #42315:
URL: https://github.com/apache/spark/pull/42315#discussion_r1283918802
##########
sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala:
##########
@@ -2272,9 +2316,7 @@ class Dataset[T] private[sql](
* @since 2.0.0
*/
def union(other: Dataset[T]): Dataset[T] = withSetOperator {
- // This breaks caching, but it's usually ok because it addresses a very
specific use case:
- // using union to union many files or partitions.
- CombineUnions(Union(logicalPlan, other.logicalPlan))
Review Comment:
Could we add a flag to `CombineUnions`?
```patch
Index:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git
a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
(revision d9d5325eed228c61d0825160477d0defaabee710)
+++
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
(date 1691116492482)
@@ -91,7 +91,7 @@
CollapseWindow,
EliminateOffsets,
EliminateLimits,
- CombineUnions,
+ CombineUnions(),
// Constant folding and strength reduction
OptimizeRepartition,
TransposeWindow,
@@ -159,7 +159,7 @@
InlineCTE()) ::
Batch("Union", Once,
RemoveNoopOperators,
- CombineUnions,
+ CombineUnions(),
RemoveNoopUnion) ::
// Run this once earlier. This might simplify the plan and reduce cost
of optimizer.
// For example, a query such as Filter(LocalRelation) would go through
all the heavy
@@ -1451,7 +1451,7 @@
/**
* Combines all adjacent [[Union]] operators into a single [[Union]].
*/
-object CombineUnions extends Rule[LogicalPlan] {
+case class CombineUnions(combineWithProject: Boolean = true) extends
Rule[LogicalPlan] {
import CollapseProject.{buildCleanedProjectList, canCollapseExpressions}
import PushProjectionThroughUnion.pushProjectionThroughUnion
@@ -1480,7 +1480,8 @@
while (stack.nonEmpty) {
stack.pop() match {
case p1 @ Project(_, p2: Project)
- if canCollapseExpressions(p1.projectList, p2.projectList,
alwaysInline = false) &&
+ if combineWithProject &&
+ canCollapseExpressions(p1.projectList, p2.projectList,
alwaysInline = false) &&
!p1.projectList.exists(SubqueryExpression.hasCorrelatedSubquery) &&
!p2.projectList.exists(SubqueryExpression.hasCorrelatedSubquery) =>
val newProjectList = buildCleanedProjectList(p1.projectList,
p2.projectList)
@@ -1499,15 +1500,17 @@
// Push down projection through Union and then push pushed plan to
Stack if
// there is a Project.
case Project(projectList, Distinct(u @ Union(children, byName,
allowMissingCol)))
- if projectList.forall(_.deterministic) && children.nonEmpty &&
+ if combineWithProject && projectList.forall(_.deterministic) &&
children.nonEmpty &&
flattenDistinct && byName == topByName && allowMissingCol ==
topAllowMissingCol =>
stack.pushAll(pushProjectionThroughUnion(projectList, u).reverse)
case Project(projectList, Deduplicate(keys: Seq[Attribute], u:
Union))
- if projectList.forall(_.deterministic) && flattenDistinct &&
u.byName == topByName &&
+ if combineWithProject &&
+ projectList.forall(_.deterministic) && flattenDistinct &&
u.byName == topByName &&
u.allowMissingCol == topAllowMissingCol && AttributeSet(keys)
== u.outputSet =>
stack.pushAll(pushProjectionThroughUnion(projectList, u).reverse)
case Project(projectList, u @ Union(children, byName,
allowMissingCol))
- if projectList.forall(_.deterministic) && children.nonEmpty &&
+ if combineWithProject &&
+ projectList.forall(_.deterministic) && children.nonEmpty &&
byName == topByName && allowMissingCol == topAllowMissingCol
=>
stack.pushAll(pushProjectionThroughUnion(projectList, u).reverse)
case child =>
```
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