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[SPARK-26572][SQL] fix aggregate codegen result evaluation #23731

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[SPARK-26572][SQL] fix aggregate codegen result evaluation #23731

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b906c8c
[SPARK-26572][SQL] fix aggregate codegen result evaluation
peter-toth Feb 3, 2019
b5d079c
indentation fix
peter-toth Feb 3, 2019
567f8f6
incorporate suggested changes
peter-toth Feb 5, 2019
5ae9add
fix review findings
peter-toth Feb 13, 2019
af861d5
fix var name
peter-toth Feb 14, 2019
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12 changes: 10 additions & 2 deletions sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/HashAggregateExec.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -466,10 +466,12 @@ case class HashAggregateExec(
val resultVars = bindReferences[Expression](
resultExpressions,
inputAttrs).map(_.genCode(ctx))
val evaluateResultVars = evaluateVariables(resultVars)
s"""
$evaluateKeyVars
$evaluateBufferVars
$evaluateAggResults
$evaluateResultVars
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@maropu maropu Feb 4, 2019

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We need this change?

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@peter-toth peter-toth Feb 4, 2019

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I think so. If you replace .distinct() to .groupBy("idx").max() in the example then this code path runs and the change fixes the same issue.

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@maropu maropu Feb 5, 2019

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If so, could you please add test cases to cover all the code paths you added in this pr.

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@peter-toth peter-toth Feb 12, 2019

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Thanks. I've added that path to the test.

${consume(ctx, resultVars)}
"""
} else if (modes.contains(Partial) || modes.contains(PartialMerge)) {
Expand Down Expand Up @@ -497,19 +499,25 @@ case class HashAggregateExec(
val resultVars = bindReferences[Expression](
resultExpressions,
inputAttrs).map(_.genCode(ctx))
val evaluateResultVars = evaluateVariables(resultVars)
s"""
$evaluateKeyVars
$evaluateResultBufferVars
$evaluateResultVars
${consume(ctx, resultVars)}
"""
} else {
// generate result based on grouping key
ctx.INPUT_ROW = keyTerm
ctx.currentVars = null
val eval = bindReferences[Expression](
val resultVars = bindReferences[Expression](
resultExpressions,
groupingAttributes).map(_.genCode(ctx))
consume(ctx, eval)
val evaluateResultVars = evaluateVariables(resultVars)
s"""
$evaluateResultVars
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@viirya viirya Feb 11, 2019

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For non broadcast join cases, the change will force evaluation unnecessarily too. We should move evaluation out of the loop in broadcast join, if possible.

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@maropu maropu Feb 12, 2019

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What I a bit concern about is; is it semantically ok to defer the evaluation of nondeterministic exprs if HashAggregateExec has these exprs?

I think, to fix this issue, its ok to modify code in the join side if we could find a simpler solution there with no performance regression. But, I have just a question about the design regardless of this issue.

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@maropu maropu Feb 12, 2019

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oh.. Kris answered my question.. in #23731 (review)

${consume(ctx, resultVars)}
"""
}
ctx.addNewFunction(funcName,
s"""
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10 changes: 10 additions & 0 deletions sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala
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Expand Up @@ -2110,4 +2110,14 @@ class DataFrameSuite extends QueryTest with SharedSQLContext {
checkAnswer(res, Row("1-1", 6, 6))
}
}

test("SPARK-26572: fix aggregate codegen result evaluation") {
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@mgaido91 mgaido91 Feb 13, 2019

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Since this is a problem with whole stage codegen, waht about moving this test to WholeStageCodegenSuite? And adding an assert that whole stage codegen is actually used, ie. the HashAggregate is a child of WholeStageCodegenExec?

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@peter-toth peter-toth Feb 13, 2019

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I'm fine with moving it to WholeStageCodegenSuite but the plan looks like:

*(3) Project [idx#4, id#6L]
+- *(3) BroadcastHashJoin [idx#4], [idx#9], Inner, BuildRight
   :- *(3) HashAggregate(keys=[idx#4], functions=[], output=[idx#4, id#6L])
   :  +- Exchange hashpartitioning(idx#4, 1)
   :     +- *(1) HashAggregate(keys=[idx#4], functions=[], output=[idx#4])
   :        +- *(1) Project [value#1 AS idx#4]
   :           +- LocalTableScan [value#1]
   +- BroadcastExchange HashedRelationBroadcastMode(List(cast(input[0, int, false] as bigint)))
      +- *(2) Project [value#1 AS idx#9]
         +- LocalTableScan [value#1]

so I guess you mean checking WholeStageCodegenExec has a ProjectExec child that has a BroadcastHashJoinExec child?

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@peter-toth peter-toth Feb 13, 2019

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Moved and added WholeStageCodegenExec check.

val baseTable = Seq((1), (1)).toDF("idx")
val distinctWithId =
baseTable.distinct.withColumn("id", functions.monotonically_increasing_id())
val res = baseTable.join(distinctWithId, "idx")
.groupBy("id").count().as("count")
.select("count")
checkAnswer(res, Row(2))
}
}