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

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Details

Type: Improvement
Status: Closed
Priority: Major
Resolution: Fixed
Affects Version/s: None
Fix Version/s: 0.5.0
Component/s: Query Processor
Labels:
None

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Release Note:

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

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

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.