Spark operator: RDD action Action action (5) -saveAsTextFile, saveAsSequenceFile, saveAsObjectFile

SaveAsTextFile

Def saveAsTextFile (path: String): Unit
Def saveAsTextFile (path: String, codec: Class [_ <: CompressionCodec]): Unit
SaveAsTextFile is used to store RDD as a text file in a file system.
The codec parameter can specify the compressed class name. 
    

  1.   Var rdd1 = sc.makeRDD (1 to 10,2)
    2. 

  2.  Scala> rdd1.saveAsTextFile ("hdfs: //cdh5/tmp/lxw1234.com/") // save to HDFS
    3. 

  3.  Hadoop fs -ls /tmp/lxw1234.com
    4. 

  4.  Found 2 items
    5. 

  5.  -rw-r-r-2 lxw1234 supergroup 0 2015-07-10 09:15 /tmp/lxw1234.com/_SUCCESS
    6. 

  6.  -rw-r-r-2 lxw1234 supergroup 21 2015-07-10 09:15 /tmp/lxw1234.com/part-00000
    7. 

  7.  
    8. 

  8.  Hadoop fs -cat /tmp/lxw1234.com/part-00000
    9. 

  9.  1
    10. 

  10.  2
    11. 

  11.  3
    12. 

  12.  4
    13. 

  13.  5
    14. 

  14.  6
    15. 

  15.  7
    16. 

  16.  8
    17. 

  17.  9
    18. 

  18.  10
    19. 

  19.  
    20.
Note: If you save a file to a local file system using rdd1.saveAsTextFile ("file: ///tmp/lxw1234.com"), only the local directory of the machine where the Executor is located is saved.
// specify the compressed format to save 
    

  1.   Rdd1.saveAsTextFile ("hdfs: //cdh5/tmp/lxw1234.com/", classOf [com.hadoop.compression.lzo.LzopCodec])
    2. 

  2.  
    3. 

  3.  Hadoop fs -ls /tmp/lxw1234.com
    4. 

  4.  -rw-r-r-2 lxw1234 supergroup 0 2015-07-10 09:20 /tmp/lxw1234.com/_SUCCESS
    5. 

  5.  -rw-r-r-2 lxw1234 supergroup 71 2015-07-10 09:20 /tmp/lxw1234.com/part-00000.lzo
    6. 

  6.  
    7. 

  7.  Hadoop fs -text /tmp/lxw1234.com/part-00000.lzo
    8. 

  8.  1
    9. 

  9.  2
    10. 

  10.  3
    11. 

  11.  4
    12. 

  12.  5
    13. 

  13.  6
    14. 

  14.  7
    15. 

  15.  8
    16. 

  16.  9
    17. 

  17.  10
    18. 

  18.  
    19. 

  19.  
    20.

SaveAsSequenceFile

SaveAsSequenceFile is used to save RDD to HDFS in the file format of SequenceFile.
Usage with saveAsTextFile.

SaveAsObjectFile

Def saveAsObjectFile (path: String): Unit
SaveAsObjectFile is used to serialize the elements in the RDD into objects and store them in a file.
For HDFS, the default is saved with SequenceFile. 
    

  1.   Var rdd1 = sc.makeRDD (1 to 10,2)
    2. 

  2.  Rdd1.saveAsObjectFile ("hdfs: //cdh5/tmp/lxw1234.com/")
    3. 

  3.  
    4. 

  4.  Hadoop fs -cat /tmp/lxw1234.com/part-00000
    5. 

  5.  SEQ! Org.apache.hadoop.io.NullWritable "org.apache.hadoop.io.BytesWritableT
    6.

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