我在spark-shell中将一个DataFrame写入hdfs，并得到以下输出。我想了解的是，什么决定了要写入的镶木地板文件的大小？我的dfs.block.size设置为：
scala> spark.sparkContext.hadoopConfiguration.get("dfs.block.size")
res1: String = 134217728
128 MB，为什么我的文件在20,000,000字节范围内？
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答案 0 :(得分：2)
实木复合地板作家不关心HDFS块的大小，因为您可以保存实木复合地板，例如在本地硬盘上。决定单个part-*。parquet文件的数量和大小的因素是数据框中的分区数（在您的情况下为64）。如果您要进行df.coalesce(1).write.parquet(...)，则只有一个很大的零件文件。
如果您希望零件文件各自约为128 Mb，则合并参数应约为20 * 64/128 =10。尽管如此，对于给定数目的合并分区依赖性，零件文件的大小并不是严格线性的。零件文件的数量越少，编码/压缩的效率越高。
有关详细信息，请参见coalesce方法说明