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[SPARK-56703][SQL] Avoid redundant propagatedFilter aliases in PlanMerger #55654

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[SPARK-56703][SQL] Avoid redundant propagatedFilter aliases in PlanMerger #55654

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171 changes: 96 additions & 75 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/PlanMerger.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -252,74 +252,12 @@ class PlanMerger(
filterPropagationSupported: Boolean): Option[TryMergeResult] = {
checkIdenticalPlans(newPlan, cachedPlan).map(TryMergeResult(cachedPlan, _)).orElse(
(newPlan, cachedPlan) match {
case (np: Project, cp: Project) =>
tryMergePlans(np.child, cp.child, filterPropagationSupported).map {
case TryMergeResult(mergedChild, npMapping, npFilter, cpFilter) =>
val (mergedProjectList, newNPMapping) =
mergeNamedExpressions(np.projectList, cp.projectList, npMapping, npFilter, cpFilter)
TryMergeResult(Project(mergedProjectList, mergedChild), newNPMapping, npFilter,
cpFilter)
}
case (np, cp: Project) =>
tryMergePlans(np, cp.child, filterPropagationSupported).map {
case TryMergeResult(mergedChild, npMapping, npFilter, cpFilter) =>
val (mergedProjectList, newNPMapping) =
mergeNamedExpressions(np.output, cp.projectList, npMapping, npFilter, cpFilter)
TryMergeResult(Project(mergedProjectList, mergedChild), newNPMapping, npFilter,
cpFilter)
}
case (np: Project, cp) =>
tryMergePlans(np.child, cp, filterPropagationSupported).map {
case TryMergeResult(mergedChild, npMapping, npFilter, cpFilter) =>
val (mergedProjectList, newNPMapping) =
mergeNamedExpressions(np.projectList, cp.output, npMapping, npFilter, cpFilter)
TryMergeResult(Project(mergedProjectList, mergedChild), newNPMapping, npFilter,
cpFilter)
}

case (np: Aggregate, cp: Aggregate) if supportedAggregateMerge(np, cp) =>
// Filter propagation into the aggregate is only safe when there is no grouping.
val childFilterPropagationSupported = filterPropagationEnabled &&
np.groupingExpressions.isEmpty && cp.groupingExpressions.isEmpty
tryMergePlans(np.child, cp.child, childFilterPropagationSupported).flatMap {
case TryMergeResult(mergedChild, npMapping, None, None) =>
val mappedNPGroupingExpression =
np.groupingExpressions.map(mapAttributes(_, npMapping))
// Order of grouping expression does matter as merging different grouping orders can
// introduce "extra" shuffles/sorts that might not present in all of the original
// subqueries.
if (mappedNPGroupingExpression.map(_.canonicalized) ==
cp.groupingExpressions.map(_.canonicalized)) {
val (mergedAggregateExpressions, newNPMapping) =
mergeNamedExpressions(np.aggregateExpressions, cp.aggregateExpressions, npMapping)
val mergedPlan =
Aggregate(cp.groupingExpressions, mergedAggregateExpressions, mergedChild)
Some(TryMergeResult(mergedPlan, newNPMapping))
} else {
None
}
case TryMergeResult(mergedChild, npMapping, npFilterOpt, cpFilterOpt) =>
// childFilterPropagationSupported guarantees both aggregates have no grouping, so
// the grouping-match check is skipped.
assert(childFilterPropagationSupported)

// Apply each propagated boolean attribute as a FILTER (WHERE ...) clause on the
// corresponding side's aggregate expressions.
// A None filter means the side's aggregate expressions already carry their individual
// FILTER attributes from a previous merge round and should be left unchanged.
// Filter propagation is consumed here and not passed further up.
val filteredNPAggregateExpressions = npFilterOpt.fold(np.aggregateExpressions) {
case (f, _) => applyFilterToAggregateExpressions(np.aggregateExpressions, f)
}
val filteredCPAggregateExpressions = cpFilterOpt.fold(cp.aggregateExpressions)(
applyFilterToAggregateExpressions(cp.aggregateExpressions, _))
val (mergedAggregateExpressions, newNPMapping) =
mergeNamedExpressions(filteredNPAggregateExpressions,
filteredCPAggregateExpressions, npMapping)
val mergedPlan = Aggregate(Seq.empty, mergedAggregateExpressions, mergedChild)
Some(TryMergeResult(mergedPlan, newNPMapping))
}

// Filter cases must precede the generic Project-peeling cases below.
// When filterPropagationSupported is true, a (Filter, Project) pair must be handled here so
// that the reuse check can find an already-aliased condition in the merged child Project.
// If (np, cp: Project) fired first, it would peel the Project layer and recurse with
// (Filter, ...), where no Project exists yet, causing a redundant alias to be created
// instead of reusing the existing one.
case (np: Filter, cp: Filter) =>
tryMergePlans(np.child, cp.child, filterPropagationSupported).flatMap {
case TryMergeResult(mergedChild, npMapping, npFilter, cpFilter) =>
Expand Down Expand Up @@ -406,13 +344,28 @@ class PlanMerger(
val newNPCondition = npFilter.fold(mappedNPCondition) {
case (f, _) => And(f, mappedNPCondition)
}
val newNPFilterAlias =
Alias(newNPCondition, s"propagatedFilter_${PlanMerger.newId}")()
val newNPFilter = newNPFilterAlias.toAttribute
val project = Project(
mergedChild.output.toList ++ Seq(newNPFilterAlias) ++ cpFilter.toSeq,
mergedChild)
TryMergeResult(project, npMapping, Some((newNPFilter, true)), cpFilter)
// If newNPCondition is already aliased in the child Project (e.g. a subsequent
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@peter-toth peter-toth May 2, 2026

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This is the new logic symmetrical to (np: Filter, cp: Filter) case.

// subplan whose filter matches one already propagated in a previous round), reuse
// the existing attribute instead of creating a redundant alias.
val existingNPFilter = mergedChild match {
case p: Project => p.projectList.collectFirst {
case a: Alias if a.child.canonicalized == newNPCondition.canonicalized =>
a.toAttribute
}
case _ => None
}
existingNPFilter match {
case Some(reusedFilter) =>
TryMergeResult(mergedChild, npMapping, Some((reusedFilter, false)), cpFilter)
case None =>
val newNPFilterAlias =
Alias(newNPCondition, s"propagatedFilter_${PlanMerger.newId}")()
val newNPFilter = newNPFilterAlias.toAttribute
val project = Project(
mergedChild.output.toList ++ Seq(newNPFilterAlias) ++ cpFilter.toSeq,
mergedChild)
TryMergeResult(project, npMapping, Some((newNPFilter, true)), cpFilter)
}
}
case (np, cp: Filter) if filterPropagationSupported =>
tryMergePlans(np, cp.child, filterPropagationSupported).collect {
Expand All @@ -431,6 +384,74 @@ class PlanMerger(
TryMergeResult(project, npMapping, npFilter, Some(newCPFilter))
}

case (np: Project, cp: Project) =>
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This is just a code move as Filter cases should come before Projects.

tryMergePlans(np.child, cp.child, filterPropagationSupported).map {
case TryMergeResult(mergedChild, npMapping, npFilter, cpFilter) =>
val (mergedProjectList, newNPMapping) =
mergeNamedExpressions(np.projectList, cp.projectList, npMapping, npFilter, cpFilter)
TryMergeResult(Project(mergedProjectList, mergedChild), newNPMapping, npFilter,
cpFilter)
}
case (np, cp: Project) =>
tryMergePlans(np, cp.child, filterPropagationSupported).map {
case TryMergeResult(mergedChild, npMapping, npFilter, cpFilter) =>
val (mergedProjectList, newNPMapping) =
mergeNamedExpressions(np.output, cp.projectList, npMapping, npFilter, cpFilter)
TryMergeResult(Project(mergedProjectList, mergedChild), newNPMapping, npFilter,
cpFilter)
}
case (np: Project, cp) =>
tryMergePlans(np.child, cp, filterPropagationSupported).map {
case TryMergeResult(mergedChild, npMapping, npFilter, cpFilter) =>
val (mergedProjectList, newNPMapping) =
mergeNamedExpressions(np.projectList, cp.output, npMapping, npFilter, cpFilter)
TryMergeResult(Project(mergedProjectList, mergedChild), newNPMapping, npFilter,
cpFilter)
}

case (np: Aggregate, cp: Aggregate) if supportedAggregateMerge(np, cp) =>
// Filter propagation into the aggregate is only safe when there is no grouping.
val childFilterPropagationSupported = filterPropagationEnabled &&
np.groupingExpressions.isEmpty && cp.groupingExpressions.isEmpty
tryMergePlans(np.child, cp.child, childFilterPropagationSupported).flatMap {
case TryMergeResult(mergedChild, npMapping, None, None) =>
val mappedNPGroupingExpression =
np.groupingExpressions.map(mapAttributes(_, npMapping))
// Order of grouping expression does matter as merging different grouping orders can
// introduce "extra" shuffles/sorts that might not present in all of the original
// subqueries.
if (mappedNPGroupingExpression.map(_.canonicalized) ==
cp.groupingExpressions.map(_.canonicalized)) {
val (mergedAggregateExpressions, newNPMapping) =
mergeNamedExpressions(np.aggregateExpressions, cp.aggregateExpressions, npMapping)
val mergedPlan =
Aggregate(cp.groupingExpressions, mergedAggregateExpressions, mergedChild)
Some(TryMergeResult(mergedPlan, newNPMapping))
} else {
None
}
case TryMergeResult(mergedChild, npMapping, npFilterOpt, cpFilterOpt) =>
// childFilterPropagationSupported guarantees both aggregates have no grouping, so
// the grouping-match check is skipped.
assert(childFilterPropagationSupported)

// Apply each propagated boolean attribute as a FILTER (WHERE ...) clause on the
// corresponding side's aggregate expressions.
// A None filter means the side's aggregate expressions already carry their individual
// FILTER attributes from a previous merge round and should be left unchanged.
// Filter propagation is consumed here and not passed further up.
val filteredNPAggregateExpressions = npFilterOpt.fold(np.aggregateExpressions) {
case (f, _) => applyFilterToAggregateExpressions(np.aggregateExpressions, f)
}
val filteredCPAggregateExpressions = cpFilterOpt.fold(cp.aggregateExpressions)(
applyFilterToAggregateExpressions(cp.aggregateExpressions, _))
val (mergedAggregateExpressions, newNPMapping) =
mergeNamedExpressions(filteredNPAggregateExpressions,
filteredCPAggregateExpressions, npMapping)
val mergedPlan = Aggregate(Seq.empty, mergedAggregateExpressions, mergedChild)
Some(TryMergeResult(mergedPlan, newNPMapping))
}

case (np: Join, cp: Join) if np.joinType == cp.joinType && np.hint == cp.hint =>
tryMergePlans(np.left, cp.left, filterPropagationSupported).flatMap {
case TryMergeResult(mergedLeft, leftNPMapping, leftNPFilter, leftCPFilter) =>
Expand Down
36 changes: 36 additions & 0 deletions sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/MergeSubplansSuite.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -853,6 +853,42 @@ class MergeSubplansSuite extends PlanTest {
}
}

test("SPARK-56703: Merge three non-grouping subqueries where the third has the same filter " +
"condition as the second") {
// subquery1 has no filter (cached as cp), subquery2 has filter a > 1 (np, propagates f0
// via the one-sided (np: Filter, cp) path), subquery3 has the identical filter a > 1.
// After subquery1+2 are merged, f0 = (a > 1) is already aliased in the merged child Project.
// When subquery3 is merged it should reuse f0 rather than creating a redundant f1.
val subquery1 = ScalarSubquery(testRelation.groupBy()(max($"a").as("max_a")))
val subquery2 = ScalarSubquery(testRelation.where($"a" > 1).groupBy()(min($"a").as("min_a")))
val subquery3 = ScalarSubquery(
testRelation.where($"a" > 1).groupBy()(count($"a").as("count_a")))
val originalQuery = testRelation.select(subquery1, subquery2, subquery3)

val f0Alias = Alias($"a" > 1, "propagatedFilter_0")()
val f0 = f0Alias.toAttribute
val mergedSubquery = testRelation
.select(testRelation.output ++ Seq(f0Alias): _*)
.groupBy()(
max($"a").as("max_a"),
min($"a", Some(f0)).as("min_a"),
count($"a", Some(f0)).as("count_a"))
.select(CreateNamedStruct(Seq(
Literal("max_a"), $"max_a",
Literal("min_a"), $"min_a",
Literal("count_a"), $"count_a"
)).as("mergedValue"))
val analyzedMergedSubquery = mergedSubquery.analyze
val correctAnswer = WithCTE(
testRelation.select(
extractorExpression(0, analyzedMergedSubquery.output, 0),
extractorExpression(0, analyzedMergedSubquery.output, 1),
extractorExpression(0, analyzedMergedSubquery.output, 2)),
Seq(definitionNode(analyzedMergedSubquery, 0)))

comparePlans(Optimize.execute(originalQuery.analyze), correctAnswer.analyze)
}

test("SPARK-40193: Do not merge non-grouping subqueries with different filter conditions when " +
"disabled") {
withSQLConf(SQLConf.MERGE_SUBPLANS_FILTER_PROPAGATION_ENABLED.key -> "false") {
Expand Down