Package org.apache.spark

Class Partitioner

Object
org.apache.spark.Partitioner
All Implemented Interfaces:
Serializable, scala.Serializable
Direct Known Subclasses:
HashPartitioner, RangePartitioner
public abstract class Partitioner extends Object implements scala.Serializable
An object that defines how the elements in a key-value pair RDD are partitioned by key. Maps each key to a partition ID, from 0 to numPartitions - 1.

Note that, partitioner must be deterministic, i.e. it must return the same partition id given the same partition key.

See Also:

  • Constructor Details

    • Partitioner

      public Partitioner()

  • Method Details

    • defaultPartitioner

      public static Partitioner defaultPartitioner(RDD<?> rdd, scala.collection.Seq<RDD<?>> others)
      Choose a partitioner to use for a cogroup-like operation between a number of RDDs.

      If spark.default.parallelism is set, we'll use the value of SparkContext defaultParallelism as the default partitions number, otherwise we'll use the max number of upstream partitions.

      When available, we choose the partitioner from rdds with maximum number of partitions. If this partitioner is eligible (number of partitions within an order of maximum number of partitions in rdds), or has partition number higher than or equal to default partitions number - we use this partitioner.

      Otherwise, we'll use a new HashPartitioner with the default partitions number.

      Unless spark.default.parallelism is set, the number of partitions will be the same as the number of partitions in the largest upstream RDD, as this should be least likely to cause out-of-memory errors.

      We use two method parameters (rdd, others) to enforce callers passing at least 1 RDD.

      Parameters:
      rdd - (undocumented)
      others - (undocumented)
      Returns:
      (undocumented)

    • numPartitions

      public abstract int numPartitions()

    • getPartition

      public abstract int getPartition(Object key)