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Posted to issues@spark.apache.org by "Dong Wang (Jira)" <ji...@apache.org> on 2019/11/09 12:53:00 UTC
[jira] [Created] (SPARK-29813) Missing persist in
mllib.PrefixSpan.findFrequentItems()
Dong Wang created SPARK-29813:
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Summary: Missing persist in mllib.PrefixSpan.findFrequentItems()
Key: SPARK-29813
URL: https://issues.apache.org/jira/browse/SPARK-29813
Project: Spark
Issue Type: Improvement
Components: MLlib
Affects Versions: 2.4.3
Reporter: Dong Wang
There are three actions in this piece of code: reduceByKey, sortBy, and collect. But data is not persisted, which will cause recomputation.
{code:scala}
private[fpm] def findFrequentItems[Item: ClassTag](
data: RDD[Array[Array[Item]]],
minCount: Long): Array[Item] = {
data.flatMap { itemsets =>
val uniqItems = mutable.Set.empty[Item]
itemsets.foreach(set => uniqItems ++= set)
uniqItems.toIterator.map((_, 1L))
}.reduceByKey(_ + _).filter { case (_, count) =>
count >= minCount
}.sortBy(-_._2).map(_._1).collect()
}
{code}
This issue is reported by our tool CacheCheck, which is used to dynamically detecting persist()/unpersist() api misuses.
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