viirya commented on a change in pull request #25827: [SPARK-29128][SQL] Split
predicate code in OR expressions
URL: https://github.com/apache/spark/pull/25827#discussion_r325486404
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
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@@ -156,6 +156,12 @@ abstract class Expression extends TreeNode[Expression] {
private def reduceCodeSize(ctx: CodegenContext, eval: ExprCode): Unit = {
// TODO: support whole stage codegen too
+ //
+ // NOTE: We could use `CodeGenerator.defineIndependentFunction` here for
the code path
+ // of the whole stage codegen. But, we don't do so now because the
performance changes that
+ // we don't expect might occur in many queries. Therefore, we currently
apply
+ // this split function to specific performance-sensitive places only,
+ // e.g., common subexpression elimination for the whole stage codegen and
OR expressions.
Review comment:
I recall that is because string-based manipulation was thought too buggy? I
didn't remember it is because of performance issue.
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