@InterfaceAudience.Public @InterfaceStability.Stable public interface RecordReader<K,V> extends Closeable
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
and Reducer
tasks for
processing. It thus assumes the responsibility of processing record
boundaries and presenting the tasks with keys and values.
InputSplit
,
InputFormat
Modifier and Type | Method and Description |
---|---|
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.
|
boolean next(K key, V value) throws IOException
key
- the key to read data intovalue
- the value to read data intoIOException
K createKey()
V createValue()
long getPos() throws IOException
IOException
void close() throws IOException
InputSplit
to future operations.close
in interface AutoCloseable
close
in interface Closeable
IOException
float getProgress() throws IOException
RecordReader
consumed i.e.
has been processed by?0.0
to 1.0
.IOException
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