spark获取指定分区数据

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使用 mapPartitionsWithIndex 如下所示

// Create (1, 1), (2, 2), ..., (100, 100) dataset
// and partition by key so we know what to expect
val rdd = sc.parallelize((1 to 100) map (i => (i, i)), 16)
  .partitionBy(new org.apache.spark.HashPartitioner(8))

val zeroth = rdd
  // If partition number is not zero ignore data
  .mapPartitionsWithIndex((idx, iter) => if (idx == 0) iter else Iterator())

// Check if we get expected results 8, 16, ..., 96
assert (zeroth.keys.map(_ % 8 == 0).reduce(_ & _) & zeroth.count == 12)