anilkanike / hive-orc-mr

Hive ORC File Format MapReduce Examples

Applications based on hadoop & hbase

Env

• Hive-0.11.0
• Hadoop-1.1.2
• JDK-1.6.0_35 +

ORC File Format

The Optimized Row Columnar (ORC) file format provides a highly efficient way to store Hive data. It was designed to overcome limitations of the other Hive file formats. Using ORC files improves performance when Hive is reading, writing, and processing data.

Compared with RCFile format, for example, ORC file format has many advantages such as:

• a single file as the output of each task, which reduces the NameNode's load
• Hive type support including datetime, decimal, and the complex types (struct, list, map, and union)
• light-weight indexes stored within the file
  • skip row groups that don't pass predicate filtering
  • seek to a given row
• block-mode compression based on data type
  • run-length encoding for integer columns
  • dictionary encoding for string columns
• concurrent reads of the same file using separate RecordReaders
• ability to split files without scanning for markers
• bound the amount of memory needed for reading or writing
• metadata stored using Protocol Buffers, which allows addition and removal of fields

ORC related HQL

CREATE EXTERNAL TABLE test.test_20130728_orc(
  stat_date string, 
  stat_hour string, 
  ip string, 
  logdate string, 
  method string, 
  url string, 
  uid string, 
  pid string, 
  aid int, 
  wid int, 
  vid int, 
  type int, 
  stat int, 
  mtime float, 
  ptime float, 
  channel string, 
  boxver string, 
  bftime int, 
  country string, 
  province string, 
  city string, 
  isp string, 
  ditchid int, 
  drm int, 
  charge int, 
  ad int, 
  adclick int, 
  groupid int, 
  client int, 
  usertype int, 
  ptolemy int, 
  fixedid string, 
  userid string) 
STORED AS ORC 
LOCATION "/data/test/20130728_orc"
tblproperties ("orc.compress"="ZLIB");

INSERT OVERWRITE TABLE test.test_20130728_orc SELECT * FROM test.test_20130728;