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SPARK-1628: Add missing hashCode methods in Partitioner subclasses #549

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SPARK-1628: Add missing hashCode methods in Partitioner subclasses #549

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17 changes: 16 additions & 1 deletion core/src/main/scala/org/apache/spark/Partitioner.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,8 @@ class HashPartitioner(partitions: Int) extends Partitioner {
case _ =>
false
}

override def hashCode: Int = numPartitions
}

/**
Expand Down Expand Up @@ -119,7 +121,7 @@ class RangePartitioner[K : Ordering : ClassTag, V](
}
}

def numPartitions = partitions
def numPartitions = rangeBounds.length + 1
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@zsxwing zsxwing Apr 25, 2014

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If using numPartitions = partitions, there is a chance that p1 == p2 && p1.numPartitions != p2.numPartitions is true. For example, if rdd.sample is empty, p1 = new RangePartitioner[...](10, rdd, true), and p2 = new RangePartitioner[...](1, rdd, true).

That's confusing. So I changed partitions to rangeBounds.length + 1.


private val binarySearch: ((Array[K], K) => Int) = CollectionsUtils.makeBinarySearch[K]

Expand Down Expand Up @@ -155,4 +157,17 @@ class RangePartitioner[K : Ordering : ClassTag, V](
case _ =>
false
}


override def hashCode(): Int = {
val prime = 31
var result = 1
var i = 0
while (i < rangeBounds.length) {
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@srowen srowen Apr 25, 2014

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Could this be simplified a lot with Arrays.hashCode()?

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@zsxwing zsxwing Apr 25, 2014

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There is not a generics Arrays.hashCode. Arrays.hashCode(rangeBounds) cannot be compiled.

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@srowen srowen Apr 25, 2014

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Darn, java.util.Arrays.hashCode(Object[]) doesn't match any scala array? java.util.Arrays.hashCode(Array(1,2,3)) works fine but that's not quite the situation here. Oh well. Maybe wrap as a List and use its hashCode? may not be worth it to save the code.

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@zsxwing zsxwing Apr 25, 2014

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Maybe Scala compiler can not determine that using which one here: Arrays.hashCode(Object[]), Arrays.hashCode(int[]), or Arrays.hashCode(double[])...

result = prime * result + rangeBounds(i).hashCode
i += 1
}
result = prime * result + ascending.hashCode
result
}
}
2 changes: 2 additions & 0 deletions core/src/main/scala/org/apache/spark/api/python/PythonPartitioner.scala
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Expand Up @@ -50,4 +50,6 @@ private[spark] class PythonPartitioner(
case _ =>
false
}

override def hashCode: Int = 31 * numPartitions + pyPartitionFunctionId.hashCode
}
2 changes: 2 additions & 0 deletions examples/src/main/scala/org/apache/spark/examples/bagel/PageRankUtils.scala
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Expand Up @@ -124,4 +124,6 @@ class CustomPartitioner(partitions: Int) extends Partitioner {
c.numPartitions == numPartitions
case _ => false
}

override def hashCode: Int = numPartitions
}