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From: liancheng <git@git.apache.org>
To: dev@spark.apache.org
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References: <git-pr-96-spark@git.apache.org>
In-Reply-To: <git-pr-96-spark@git.apache.org>
Subject: [GitHub] spark pull request: [SPARK-1194] Fix the same-RDD rule for
 cache r...
Content-Type: text/plain
Message-Id: <20140307170243.D4BC593FF22@tyr.zones.apache.org>
Date: Fri,  7 Mar 2014 17:02:43 +0000 (UTC)

Github user liancheng commented on a diff in the pull request:

    https://github.com/apache/spark/pull/96#discussion_r10390021
  
    --- Diff: core/src/main/scala/org/apache/spark/storage/MemoryStore.scala ---
    @@ -236,13 +236,23 @@ private class MemoryStore(blockManager: BlockManager, maxMemory: Long)
             while (maxMemory - (currentMemory - selectedMemory) < space && iterator.hasNext) {
               val pair = iterator.next()
               val blockId = pair.getKey
    -          if (rddToAdd.isDefined && rddToAdd == getRddId(blockId)) {
    -            logInfo("Will not store " + blockIdToAdd + " as it would require dropping another " +
    -              "block from the same RDD")
    -            return false
    +          // Apply the same-RDD rule for cache replacement. Quoted from the
    +          // original RDD paper:
    +          //
    +          //    When a new RDD partition is computed but there is not enough
    +          //    space to store it, we evict a partition from the least recently
    +          //    accessed RDD, unless this is the same RDD as the one with the
    +          //    new partition. In that case, we keep the old partition in memory
    +          //    to prevent cycling partitions from the same RDD in and out.
    +          //
    +          // TODO implement LRU eviction
    +          rddToAdd match {
    +            case Some(rddId) if rddId == getRddId(blockId) =>
    --- End diff --
    
    Made a mistake here, `rddId: Int == getRddId(blockId): Option[Int]` never holds...


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