Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/18931#discussion_r163512972
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/WholeStageCodegenExec.scala
---
@@ -156,13 +156,94 @@ trait CodegenSupport extends SparkPlan {
ctx.INPUT_ROW = null
ctx.freshNamePrefix = parent.variablePrefix
val evaluated = evaluateRequiredVariables(output, inputVars,
parent.usedInputs)
+
+ // Under certain conditions, we can put the logic to consume the rows
of this operator into
+ // another function. So we can prevent a generated function too long
to be optimized by JIT.
+ // The conditions:
+ // 1. The config "SQLConf.DECOUPLE_OPERATOR_CONSUME_FUNCTIONS" is
enabled.
+ // 2. The parent uses all variables in output. we can't defer variable
evaluation when consume
+ // in another function.
+ // 3. The output variables are not empty. If it's empty, we don't
bother to do that.
+ // 4. We don't use row variable. The construction of row uses deferred
variable evaluation. We
--- End diff --
I think what we need is `inputVars` are all materialized, which can be
guaranteed by `requireAllOutput` and `outputVars != null`
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