liupc opened a new pull request #23693: [SPARK-26768][CORE]Remove useless code in BlockManager URL: https://github.com/apache/spark/pull/23693 ## What changes were proposed in this pull request? Recently, when I was reading some code of `BlockManager.getBlockData`, I found that there are useless code that would never reach. The related codes is as below: ``` override def getBlockData(blockId: BlockId): ManagedBuffer = { if (blockId.isShuffle) { shuffleManager.shuffleBlockResolver.getBlockData(blockId.asInstanceOf[ShuffleBlockId]) } else { getLocalBytes(blockId) match { case Some(blockData) => new BlockManagerManagedBuffer(blockInfoManager, blockId, blockData, true) case None => // If this block manager receives a request for a block that it doesn't have then it's // likely that the master has outdated block statuses for this block. Therefore, we send // an RPC so that this block is marked as being unavailable from this block manager. reportBlockStatus(blockId, BlockStatus.empty) throw new BlockNotFoundException(blockId.toString) } } } ``` ``` def getLocalBytes(blockId: BlockId): Option[BlockData] = { logDebug(s"Getting local block $blockId as bytes") // As an optimization for map output fetches, if the block is for a shuffle, return it // without acquiring a lock; the disk store never deletes (recent) items so this should work if (blockId.isShuffle) { val shuffleBlockResolver = shuffleManager.shuffleBlockResolver // TODO: This should gracefully handle case where local block is not available. Currently // downstream code will throw an exception. val buf = new ChunkedByteBuffer( shuffleBlockResolver.getBlockData(blockId.asInstanceOf[ShuffleBlockId]).nioByteBuffer()) Some(new ByteBufferBlockData(buf, true)) } else { blockInfoManager.lockForReading(blockId).map { info => doGetLocalBytes(blockId, info) } } } ``` the `blockId.isShuffle` is checked twice, but however it seems that in the method calling hierarchy of `BlockManager.getLocalBytes`, the another callsite of the `BlockManager.getLocalBytes` is at `TorrentBroadcast.readBlocks` where the blockId can never be a `ShuffleBlockId`.  So I think we should remove these useless code for easy reading. ## How was this patch tested? NA Please review http://spark.apache.org/contributing.html before opening a pull request.
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