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[SPARK-22215][SQL] Add configuration to set the threshold for generated class #19447

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[SPARK-22215][SQL] Add configuration to set the threshold for generated class #19447

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c69be31
[SPARK-22215][SQL] Add configuration to set the threshold for generat…
mgaido91 Oct 6, 2017
ed8aaea
use SQLConf instead of SparkEnv
mgaido91 Oct 6, 2017
4c68de6
add internal and check
mgaido91 Oct 6, 2017
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8 changes: 5 additions & 3 deletions ...lyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala
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Expand Up @@ -279,11 +279,13 @@ class CodegenContext {
inlineToOuterClass: Boolean = false): String = {
// The number of named constants that can exist in the class is limited by the Constant Pool
// limit, 65,536. We cannot know how many constants will be inserted for a class, so we use a
// threshold of 1600k bytes to determine when a function should be inlined to a private, nested
// sub-class.
// threshold to determine when a function should be inlined to a private, nested sub-class
val generatedClassLengthThreshold = SparkEnv.get.conf.getInt(
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@kiszk kiszk Oct 6, 2017

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Can you ensure SparkEnv.get is always true?

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@mgaido91 mgaido91 Oct 6, 2017

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Can this be empty? In

spark/sql/catalyst/src/main/java/org/apache/spark/sql/execution/UnsafeExternalRowSorter.java

Line 80 in 83488cc

final SparkEnv sparkEnv = SparkEnv.get();
there is no check about it being None...

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@kiszk kiszk Oct 6, 2017

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The code that you pointed out is not in CodeGenerator.scala. In my case at CodeGenerator.scala, there are some cases that SparkEnv.get is null. If you have not seen this null in you case, it would be good.
@gatorsmile will implement a better approach to get this conf soon.

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@maropu maropu Oct 6, 2017

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you better refer other code in CodeGenerate:

https://github.com/mgaido91/spark/blob/c69be31314d9aa96c3920073beaf7cca46d507fa/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala#L934

SQLConf.GENERATED_CLASS_LENGTH_THRESHOLD.key,
SQLConf.GENERATED_CLASS_LENGTH_THRESHOLD.defaultValue.get)
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@dongjoon-hyun dongjoon-hyun Oct 6, 2017

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Could you simplify the above three lines into the following?

val generatedClassLengthThreshold = SparkEnv.get.conf.get(
  SQLConf.GENERATED_CLASS_LENGTH_THRESHOLD)

val (className, classInstance) = if (inlineToOuterClass) {
outerClassName -> ""
} else if (currClassSize > 1600000) {
} else if (currClassSize > generatedClassLengthThreshold) {
val className = freshName("NestedClass")
val classInstance = freshName("nestedClassInstance")

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9 changes: 9 additions & 0 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
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Expand Up @@ -934,6 +934,15 @@ object SQLConf {
.intConf
.createWithDefault(10000)

val GENERATED_CLASS_LENGTH_THRESHOLD =
buildConf("spark.sql.codegen.generatedClass.size.threshold")
.doc("Threshold in bytes for the size of a generated class. If the generated class " +
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@maropu maropu Oct 6, 2017

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Please add .internal(). I think this is not a parameter for users.

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@mgaido91 mgaido91 Oct 6, 2017 •
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Sorry for my ignorance. If users cannot set it, how can this parameter be changed?

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@maropu maropu Oct 6, 2017

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I think this is not a frequently-used parameter for users. Also, other JVM implimentation-specific parameters are internal, e.g., WHOLESTAGE_HUGE_METHOD_LIMIT. cc: @rednaxelafx

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@mgaido91 mgaido91 Oct 6, 2017

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I agree with you, but might you please explain me how to set a parameter which is internal? Thanks.

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@maropu maropu Oct 6, 2017

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Users can change this value in the same way with other public parameters, but internal just means that parameters are not explicitly exposed to users.

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@mgaido91 mgaido91 Oct 6, 2017

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thanks for the explanation, I'll add it immediately.

"size is higher of this value, a private nested class is created and used." +
"This is useful to limit the number of named constants in the class " +
"and therefore its Constant Pool. The default is 1600k.")
.intConf
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@dongjoon-hyun dongjoon-hyun Oct 6, 2017

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Please add .checkValue here with a valid minimum and maximum.

.createWithDefault(1600000)

object Deprecated {
val MAPRED_REDUCE_TASKS = "mapred.reduce.tasks"
}
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