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[MINOR][SQL] Some errors in the notes. #23280

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[MINOR][SQL] Some errors in the notes. #23280

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2 changes: 1 addition & 1 deletion sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/package.scala
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Expand Up @@ -101,7 +101,7 @@ package object expressions {
StructType(attrs.map(a => StructField(a.name, a.dataType, a.nullable, a.metadata)))
}

// It's possible that `attrs` is a linked list, which can lead to bad O(n^2) loops when
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@dongjoon-hyun dongjoon-hyun Dec 11, 2018 •
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Could you tell us why you think this comment is error? This comments came from SPARK-15764 Replace N^2 loop in BindReferences to explain the problamatic situation.

When using ordinals to access linked list, the time cost is O(n).

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@CarolinePeng CarolinePeng Dec 11, 2018

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The cost time to access the linked list using ordinal is O (n), but I do not combine BindReferences to analyze the cost time.

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@dongjoon-hyun dongjoon-hyun Dec 11, 2018

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Ya. The original sentence has a different context at that time.

// It's possible that `attrs` is a linked list, which can lead to bad O(n) loops when
// accessing attributes by their ordinals. To avoid this performance penalty, convert the input
// to an array.
@transient private lazy val attrsArray = attrs.toArray
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2 changes: 1 addition & 1 deletion sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
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Expand Up @@ -93,7 +93,7 @@ abstract class LogicalPlan
/**
* Optionally resolves the given strings to a [[NamedExpression]] using the input from all child
* nodes of this LogicalPlan. The attribute is expressed as
* as string in the following form: `[scope].AttributeName.[nested].[fields]...`.
* string in the following form: `[scope].AttributeName.[nested].[fields]...`.
*/
def resolveChildren(
nameParts: Seq[String],
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