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## org.apache.cassandra.hadoop
Class ColumnFamilyInputFormat

    java.lang.Object
      org.apache.hadoop.mapreduce.InputFormat<java.lang.String,java.util.SortedMap<byte[],IColumn>>
          org.apache.cassandra.hadoop.ColumnFamilyInputFormat

    public class ColumnFamilyInputFormat

extends org.apache.hadoop.mapreduce.InputFormat<java.lang.String,java.util.SortedMap<byte[],IColumn>>

Hadoop InputFormat allowing map/reduce against Cassandra rows within one ColumnFamily. At minimum, you need to set the CF and predicate (description of columns to extract from each row) in your Hadoop job Configuration. The ConfigHelper class is provided to make this simple: ConfigHelper.setColumnFamily ConfigHelper.setSlicePredicate You can also configure the number of rows per InputSplit with ConfigHelper.setInputSplitSize This should be "as big as possible, but no bigger." Each InputSplit is read from Cassandra with multiple get_slice_range queries, and the per-call overhead of get_slice_range is high, so larger split sizes are better -- but if it is too large, you will run out of memory. The default split size is 64k rows.

Constructor Summary
`ColumnFamilyInputFormat()`

Method Summary
`org.apache.hadoop.mapreduce.RecordReader<java.lang.String,java.util.SortedMap<byte[],IColumn>>` | `createRecordReader(org.apache.hadoop.mapreduce.InputSplit inputSplit, org.apache.hadoop.mapreduce.TaskAttemptContext taskAttemptContext)`
`java.util.List<org.apache.hadoop.mapreduce.InputSplit>` | `getSplits(org.apache.hadoop.mapreduce.JobContext context)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### ColumnFamilyInputFormat

    public ColumnFamilyInputFormat()

Method Detail

### getSplits

    public java.util.List<org.apache.hadoop.mapreduce.InputSplit> getSplits(org.apache.hadoop.mapreduce.JobContext context)
                                                                     throws java.io.IOException

  Specified by:
    `getSplits` in class `org.apache.hadoop.mapreduce.InputFormat<java.lang.String,java.util.SortedMap<byte[],IColumn>>`
  Throws:
    `java.io.IOException`

### createRecordReader

    public org.apache.hadoop.mapreduce.RecordReader<java.lang.String,java.util.SortedMap<byte[],IColumn>> createRecordReader(org.apache.hadoop.mapreduce.InputSplit inputSplit,
                                                                                                                             org.apache.hadoop.mapreduce.TaskAttemptContext taskAttemptContext)
                                                                                                                      throws java.io.IOException,
                                                                                                                             java.lang.InterruptedException

  Specified by:
    `createRecordReader` in class `org.apache.hadoop.mapreduce.InputFormat<java.lang.String,java.util.SortedMap<byte[],IColumn>>`
  Throws:
    `java.io.IOException`
    `java.lang.InterruptedException`

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Copyright © 2010 The Apache Software Foundation