Github user JoshRosen commented on a diff in the pull request: https://github.com/apache/spark/pull/10894#discussion_r52691349 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateOrdering.scala --- @@ -138,3 +138,32 @@ object GenerateOrdering extends CodeGenerator[Seq[SortOrder], Ordering[InternalR CodeGenerator.compile(code).generate(ctx.references.toArray).asInstanceOf[BaseOrdering] } } + +/** + * A lazily generate row ordering comparator. + */ +class LazilyGenerateOrdering(val ordering: Seq[SortOrder]) extends Ordering[InternalRow] { + + def this(ordering: Seq[SortOrder], inputSchema: Seq[Attribute]) = + this(ordering.map(BindReferences.bindReference(_, inputSchema))) + + @transient + lazy val generatedOrdering = GenerateOrdering.generate(ordering) --- End diff -- Will this use of `lazy val` incur a performance penalty due to having to check whether it has been initialized on each call to `compare()`? If so, I wonder whether we could eagerly initialize the ordering in the constructor then re-initialize on executors as part of `readObject()`, e.g. `@transient private[this] var generatedOrdering = ...`
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