[HADOOP-3019] want input sampler & sorted partitioner

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.19.0
• Hadoop Flags: Reviewed
• Release Note: Added a partitioner that effects a total order of output data, and an input sampler for generating the partition keyset for TotalOrderPartitioner for when the map's input keytype and distribution approximates its output.
• Assignee: Christopher Douglas
• Reporter: Doug Cutting
• Created: 14/Mar/08 16:22
• Updated: 08/Jul/09 16:52
• Resolved: 19/Sep/08 23:39

Description

The input sampler should generate a small, random sample of the input, saved to a file.

The partitioner should read the sample file and partition keys into relatively even-sized key-ranges, where the partition numbers correspond to key order.

Note that when the sampler is used for partitioning, the number of samples required is proportional to the number of reduce partitions. 10x the intended reducer count should give good results.

Issue Links

• is blocked by: HADOOP-4151 Add a memcmp-compatible interface for key types