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[SPARK-26909][FOLLOWUP][SQL] use unsafeRow.hashCode() as hash value in HashAggregate #23821

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[SPARK-26909][FOLLOWUP][SQL] use unsafeRow.hashCode() as hash value in HashAggregate #23821

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[SPARK-26909][FOLLOWUP][SQL] use unsafeRow.hashCode() as hash value i…
yucai Feb 18, 2019
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yucai Feb 18, 2019
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14 changes: 4 additions & 10 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 @@ -742,6 +742,7 @@ case class HashAggregateExec(
val fastRowKeys = ctx.generateExpressions(
bindReferences[Expression](groupingExpressions, child.output))
val unsafeRowKeys = unsafeRowKeyCode.value
val unsafeRowKeyHash = ctx.freshName("unsafeRowKeyHash")
val unsafeRowBuffer = ctx.freshName("unsafeRowAggBuffer")
val fastRowBuffer = ctx.freshName("fastAggBuffer")

Expand All @@ -755,13 +756,6 @@ case class HashAggregateExec(
}
}

// generate hash code for key
// SPARK-24076: HashAggregate uses the same hash algorithm on the same expressions
// as ShuffleExchange, it may lead to bad hash conflict when shuffle.partitions=8192*n,
// pick a different seed to avoid this conflict
val hashExpr = Murmur3Hash(groupingExpressions, 48)
val hashEval = BindReferences.bindReference(hashExpr, child.output).genCode(ctx)

val (checkFallbackForGeneratedHashMap, checkFallbackForBytesToBytesMap, resetCounter,
incCounter) = if (testFallbackStartsAt.isDefined) {
val countTerm = ctx.addMutableState(CodeGenerator.JAVA_INT, "fallbackCounter")
Expand All @@ -777,11 +771,11 @@ case class HashAggregateExec(
s"""
|// generate grouping key
|${unsafeRowKeyCode.code}
|${hashEval.code}
|int $unsafeRowKeyHash = ${unsafeRowKeyCode.value}.hashCode();
|if ($checkFallbackForBytesToBytesMap) {
| // try to get the buffer from hash map
| $unsafeRowBuffer =
| $hashMapTerm.getAggregationBufferFromUnsafeRow($unsafeRowKeys, ${hashEval.value});
| $hashMapTerm.getAggregationBufferFromUnsafeRow($unsafeRowKeys, $unsafeRowKeyHash);
|}
|// Can't allocate buffer from the hash map. Spill the map and fallback to sort-based
|// aggregation after processing all input rows.
Expand All @@ -795,7 +789,7 @@ case class HashAggregateExec(
| // the hash map had be spilled, it should have enough memory now,
| // try to allocate buffer again.
| $unsafeRowBuffer = $hashMapTerm.getAggregationBufferFromUnsafeRow(
| $unsafeRowKeys, ${hashEval.value});
| $unsafeRowKeys, $unsafeRowKeyHash);
| if ($unsafeRowBuffer == null) {
| // failed to allocate the first page
| throw new $oomeClassName("No enough memory for aggregation");
Expand Down