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[SPARK-42132][SQL] Deduplicate attributes in groupByKey.cogroup #39673

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EnricoMi wants to merge 9 commits into from
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[SPARK-42132][SQL] Deduplicate attributes in groupByKey.cogroup #39673

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501a80f
Test and fix cogrouping same dataframe deduplication issue
EnricoMi Jan 18, 2023
b0f5ea6
Remove unrelated tests, improve comments
EnricoMi Jan 20, 2023
eec3c98
Rewrite right sort order
EnricoMi Jan 25, 2023
0bde873
Add test for sorted cogroup on duplicate reference
EnricoMi Jan 25, 2023
023c199
Remove right order from deduplication
EnricoMi Jan 25, 2023
4424820
Finish test, rewording comments
EnricoMi Jan 25, 2023
c8dfd9d
Move tests into DatasetSuite
EnricoMi Jan 30, 2023
25fa797
Adjust tests for AppendColumns fix
EnricoMi Jan 26, 2023
cc5773c
Remove cogroupSorted tests
EnricoMi Jan 26, 2023
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Remove right order from deduplication
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@EnricoMi
EnricoMi committed Jun 30, 2023
commit 023c1993fc55a22c5e4435af6cc43c56d02745de
10 changes: 4 additions & 6 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/object.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -689,18 +689,16 @@ object CoGroup {
attrs.map(attr => duplicateAttributes.getOrElse(attr, attr))
}

val (dedupRightGroup, dedupRightAttr, dedupRightOrder, dedupRight) =
// rightOrder is resolved against right plan, so deduplication not needed
val (dedupRightGroup, dedupRightAttr, dedupRight) =
if (duplicateAttributes.nonEmpty) {
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@cloud-fan cloud-fan Apr 26, 2023

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it's a bit weird to do dedup here. Can we update the DeduplicateRelations rule to handle CoGroup specially?

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@EnricoMi EnricoMi Apr 26, 2023 •
edited
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I don't really see how DeduplicateRelations can be modified to not rewrite all attributes of CoGroup.

In DeduplicateRelations.apply method renewDuplicatedRelations is called, which calls rewriteAttrs(attrMap) on the CoGroup, which rewrites all attributes.

If you are suggesting to add case cogroup @ CoGroup(...) => to

spark/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/DeduplicateRelations.scala

Lines 45 to 83 in f1a6c5e

newPlan.resolveOperatorsUpWithPruning(
_.containsAnyPattern(JOIN, LATERAL_JOIN, AS_OF_JOIN, INTERSECT, EXCEPT, UNION, COMMAND),
ruleId) {
case p: LogicalPlan if !p.childrenResolved => p
// To resolve duplicate expression IDs for Join.
case j @ Join(left, right, _, _, _) if !j.duplicateResolved =>
j.copy(right = dedupRight(left, right))
// Resolve duplicate output for LateralJoin.
case j @ LateralJoin(left, right, _, _) if right.resolved && !j.duplicateResolved =>
j.copy(right = right.withNewPlan(dedupRight(left, right.plan)))
// Resolve duplicate output for AsOfJoin.
case j @ AsOfJoin(left, right, _, _, _, _, _) if !j.duplicateResolved =>
j.copy(right = dedupRight(left, right))
// intersect/except will be rewritten to join at the beginning of optimizer. Here we need to
// deduplicate the right side plan, so that we won't produce an invalid self-join later.
case i @ Intersect(left, right, _) if !i.duplicateResolved =>
i.copy(right = dedupRight(left, right))
case e @ Except(left, right, _) if !e.duplicateResolved =>
e.copy(right = dedupRight(left, right))
// Only after we finish by-name resolution for Union
case u: Union if !u.byName && !u.duplicateResolved =>
// Use projection-based de-duplication for Union to avoid breaking the checkpoint sharing
// feature in streaming.
val newChildren = u.children.foldRight(Seq.empty[LogicalPlan]) { (head, tail) =>
head +: tail.map {
case child if head.outputSet.intersect(child.outputSet).isEmpty =>
child
case child =>
val projectList = child.output.map { attr =>
Alias(attr, attr.name)()
}
Project(projectList, child)
}
}
u.copy(children = newChildren)
case merge: MergeIntoTable if !merge.duplicateResolved =>
merge.copy(sourceTable = dedupRight(merge.targetTable, merge.sourceTable))
}
}

then this won't work because all attributes of CoGroup have been rewritten at this point.

I'd appreciate some pointers or sketch of a solution.

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@cloud-fan cloud-fan Jul 31, 2023

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@Hisoka-X is working on it: #41554

(
dedup(rightGroup).map(_.toAttribute),
dedup(rightAttr).map(_.toAttribute),
rightOrder.map(_.transformDown {
case a: Attribute => duplicateAttributes.getOrElse(a, a)
}.asInstanceOf[SortOrder]),
Project(dedup(right.output), right)
)
} else {
(rightGroup, rightAttr, rightOrder, right)
(rightGroup, rightAttr, right)
}

val cogrouped = CoGroup(
Expand All @@ -715,7 +713,7 @@ object CoGroup {
leftAttr,
dedupRightAttr,
leftOrder,
dedupRightOrder,
rightOrder,
CatalystSerde.generateObjAttr[OUT],
left,
dedupRight)
Expand Down