bersprockets commented on a change in pull request #23392: [SPARK-26450][SQL]
Avoid rebuilding map of schema for every column in projection
URL: https://github.com/apache/spark/pull/23392#discussion_r244756738
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/package.scala
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@@ -88,8 +88,11 @@ package object expressions {
/**
* A helper function to bind given expressions to an input schema.
*/
- def toBoundExprs(exprs: Seq[Expression], inputSchema: Seq[Attribute]):
Seq[Expression] = {
- exprs.map(BindReferences.bindReference(_, inputSchema))
+ def toBoundExprs[A <: Expression](
+ exprs: Seq[A],
+ inputSchema: Seq[Attribute]): Seq[A] = {
Review comment:
Sometimes this function is called with a zero-length exprs (```df.count```,
for example). I am attempting to avoid constructing the AttributeSeq in that
case, because AttributeSeq's constructor eagerly builds a data structure based
on the attributes (```private val qualified3Part```).
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