Showing content from https://hadoop.apache.org/docs/r1.2.1/api/org/apache/hadoop/mapred/RecordReader.html below:
RecordReader (Hadoop 1.2.1 API)
org.apache.hadoop.mapred
Interface RecordReader<K,V>
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All Known Subinterfaces:
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ComposableRecordReader<K,V>
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All Known Implementing Classes:
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CombineFileRecordReader, DBInputFormat.DBRecordReader, InnerJoinRecordReader, JoinRecordReader, KeyValueLineRecordReader, LineDocRecordReader, LineRecordReader, MultiFileWordCount.MultiFileLineRecordReader, MultiFilterRecordReader, OuterJoinRecordReader, OverrideRecordReader, SequenceFileAsBinaryInputFormat.SequenceFileAsBinaryRecordReader, SequenceFileAsTextRecordReader, SequenceFileRecordReader, StreamBaseRecordReader, StreamXmlRecordReader, WrappedRecordReader
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public interface RecordReader<K,V>
RecordReader reads <key, value> pairs from an InputSplit.
RecordReader, typically, converts the byte-oriented view of the input, provided by the InputSplit, and presents a record-oriented view for the Mapper & Reducer tasks for processing. It thus assumes the responsibility of processing record boundaries and presenting the tasks with keys and values.
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See Also:
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InputSplit, InputFormat
Method Summary void close()
Close this InputSplit to future operations. K createKey()
Create an object of the appropriate type to be used as a key. V createValue()
Create an object of the appropriate type to be used as a value. long getPos()
Returns the current position in the input. float getProgress()
How much of the input has the RecordReader consumed i.e. boolean next(K key, V value)
Reads the next key/value pair from the input for processing. next
boolean next(K key,
V value)
throws IOException
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Reads the next key/value pair from the input for processing.
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Parameters:
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key - the key to read data into
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value - the value to read data into
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Returns:
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true iff a key/value was read, false if at EOF
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Throws:
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IOException
createKey
K createKey()
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Create an object of the appropriate type to be used as a key.
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Returns:
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a new key object.
createValue
V createValue()
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Create an object of the appropriate type to be used as a value.
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Returns:
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a new value object.
getPos
long getPos()
throws IOException
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Returns the current position in the input.
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Returns:
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the current position in the input.
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Throws:
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IOException
close
void close()
throws IOException
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Close this
InputSplit to future operations.
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Throws:
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IOException
getProgress
float getProgress()
throws IOException
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How much of the input has the
RecordReader consumed i.e. has been processed by?
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Returns:
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progress from
0.0 to 1.0.
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Throws:
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IOException
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