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[SPARK-13771][SQL][WIP] Eliminate child columns from project if the project with no references to its child #11602

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[SPARK-13771][SQL][WIP] Eliminate child columns from project if the project with no references to its child #11602

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4 changes: 4 additions & 0 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -381,6 +381,10 @@ object ColumnPruning extends Rule[LogicalPlan] {
p
}

// Eliminate the child from the Projects with no references to its child
case p @ Project(projectList, child) if p.references.intersect(child.outputSet).isEmpty =>
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@cloud-fan cloud-fan Mar 9, 2016

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But this will change the number of rows right?

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@viirya viirya Mar 9, 2016

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Yea. I think it is changed to 1 row. Indeed this causes problem.

Project(projectList, OneRowRelation)

// Can't prune the columns on LeafNode
case p @ Project(_, l: LeafNode) => p

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14 changes: 14 additions & 0 deletions sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ColumnPruningSuite.scala
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Expand Up @@ -284,5 +284,19 @@ class ColumnPruningSuite extends PlanTest {
comparePlans(Optimize.execute(plan1.analyze), correctAnswer1)
}

test("Eliminate the Project with no references to its child") {
val expectedInput = OneRowRelation
val expected = Project(Literal(1).as("1") :: Nil, expectedInput).analyze

val input = LocalRelation('key.int, 'value.string)
val query1 =
Project(Literal(1).as("1") :: Nil, Project(Literal(1).as("1") :: Nil, input)).analyze
comparePlans(Optimize.execute(query1), expected)

val query2 =
Project(Literal(1).as("1") :: Nil, Project(Nil, input)).analyze
comparePlans(Optimize.execute(query2), expected)
}

// todo: add more tests for column pruning
}