[HIVE-74] Hive can use CombineFileInputFormat for when the input are many small files

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.5.0
• Component/s: Query Processor
• Hadoop Flags: Reviewed

Release Note

HIVE-74. Hive can use CombineFileInputFormat for when the input has many
small files (Namit Jain via rmurthy)

• Assignee: Rajesh Balamohan
• Reporter: Dhruba Borthakur
• Created: 20/Nov/08 09:40
• Updated: 26/Jan/16 00:03
• Resolved: 15/Sep/09 00:07

Description

There are cases when the input to a Hive job are thousands of small files. In this case, there is a mapper for each file. Most of the overhead for spawning all these mappers can be avoided if Hive used CombineFileInputFormat introduced via HADOOP-4565

Options to control this behavior:

hive.input.format (org.apache.hadoop.hive.ql.io.CombineHiveInputFormat (default, if empty), or org.apache.hadoop.hive.ql.io.HiveInputFormat)
mapred.min.split.size.per.node (the minimum bytes of data to create a node-local partition, otherwise the data will combine to rack level. default:0)
mapred.min.split.size.per.rack (the minimum bytes of data to create a rack-local partition, otherwise the data will combine to global level. default:0)
mapred.max.split.size (the max size of each split, will be exceeded because we stop accumulating *after* reaching it, instead of before)

The 3 numbers above must be in non-descending order.

Issue Links

• blocks: HIVE-826 cleanup HiveInputFormat.getRecordReader()
• is blocked by: HADOOP-4565 MultiFileInputSplit can use data locality information to create splits
• is related to: HIVE-826 cleanup HiveInputFormat.getRecordReader()
• is related to: HIVE-824 use same mapper for mltiple directories
• relates to: HIVE-824 use same mapper for mltiple directories