[HIVE-17935] Turn on hive.optimize.sort.dynamic.partition by default

• Type: Bug
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Andrew Sherman
• Created: 30/Oct/17 18:15
• Updated: 12/Dec/18 02:55

Description

The config option hive.optimize.sort.dynamic.partition is an optimization for Hive’s dynamic partitioning feature. It was originally implemented in HIVE-6455. With this optimization, the dynamic partition columns and bucketing columns (in case of bucketed tables) are sorted before being fed to the reducers. Since the partitioning and bucketing columns are sorted, each reducer can keep only one record writer open at any time thereby reducing the memory pressure on the reducers. There were some early problems with this optimization and it was disabled by default in HiveConf in HIVE-8151. Since then setting hive.optimize.sort.dynamic.partition=true has been used to solve problems where dynamic partitioning produces with (1) too many small files on HDFS, which is bad for the cluster and can increase overhead for future Hive queries over those partitions, and (2) OOM issues in the map tasks because it trying to simultaneously write to 100 different files.

It now seems that the feature is probably mature enough that it can be enabled by default.