Package org.apache.hadoop.io.file.tfile

Class TFile.Reader.Scanner

java.lang.Object

org.apache.hadoop.io.file.tfile.TFile.Reader.Scanner

All Implemented Interfaces:

Closeable, AutoCloseable

Enclosing class:

TFile.Reader

public static class TFile.Reader.Scanner
extends Object
implements Closeable

The TFile Scanner. The Scanner has an implicit cursor, which, upon creation, points to the first key-value pair in the scan range. If the scan range is empty, the cursor will point to the end of the scan range.

Use atEnd() to test whether the cursor is at the end location of the scanner.

Use advance() to move the cursor to the next key-value pair (or end if none exists). Use seekTo methods ( seekTo(byte[]) or seekTo(byte[], int, int)) to seek to any arbitrary location in the covered range (including backward seeking). Use rewind() to seek back to the beginning of the scanner. Use seekToEnd() to seek to the end of the scanner.

Actual keys and values may be obtained through TFile.Reader.Scanner.Entry object, which is obtained through entry().

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
class	TFile.Reader.Scanner.Entry	Entry to a <Key, Value> pair.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Scanner(TFile.Reader reader, long offBegin, long offEnd)	Constructor
protected	Scanner(TFile.Reader reader, RawComparable beginKey, RawComparable endKey)	Constructor

Method Summary

Modifier and Type	Method	Description
boolean	advance()	Move the cursor to the next key-value pair.
boolean	atEnd()	Is cursor at the end location?
void	close()	Close the scanner.
TFile.Reader.Scanner.Entry	entry()	Get an entry to access the key and value.
long	getRecordNum()	Get the RecordNum corresponding to the entry pointed by the cursor.
void	lowerBound(byte[] key)	Move the cursor to the first entry whose key is greater than or equal to the input key.
void	lowerBound(byte[] key, int keyOffset, int keyLen)	Move the cursor to the first entry whose key is greater than or equal to the input key.
void	rewind()	Rewind to the first entry in the scanner.
boolean	seekTo(byte[] key)	Move the cursor to the first entry whose key is greater than or equal to the input key.
boolean	seekTo(byte[] key, int keyOffset, int keyLen)	Move the cursor to the first entry whose key is greater than or equal to the input key.
void	seekToEnd()	Seek to the end of the scanner.
void	upperBound(byte[] key)	Move the cursor to the first entry whose key is strictly greater than the input key.
void	upperBound(byte[] key, int keyOffset, int keyLen)	Move the cursor to the first entry whose key is strictly greater than the input key.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Scanner

protected Scanner(TFile.Reader reader,
 long offBegin,
 long offEnd)
           throws IOException

Constructor

Parameters:

reader - The TFile reader object.

offBegin - Begin byte-offset of the scan.

offEnd - End byte-offset of the scan.

Throws:

IOException - The offsets will be rounded to the beginning of a compressed block whose offset is greater than or equal to the specified offset.

Scanner

protected Scanner(TFile.Reader reader,
 RawComparable beginKey,
 RawComparable endKey)
           throws IOException

Constructor

Parameters:

reader - The TFile reader object.

beginKey - Begin key of the scan. If null, scan from the first <K, V> entry of the TFile.

endKey - End key of the scan. If null, scan up to the last <K, V> entry of the TFile.

Throws:

IOException - raised on errors performing I/O.

Method Details

seekTo

public boolean seekTo(byte[] key)
               throws IOException

Move the cursor to the first entry whose key is greater than or equal to the input key. Synonymous to seekTo(key, 0, key.length). The entry returned by the previous entry() call will be invalid.

Parameters:

key - The input key

Returns:

true if we find an equal key.

Throws:

IOException - raised on errors performing I/O.

seekTo

public boolean seekTo(byte[] key,
 int keyOffset,
 int keyLen)
               throws IOException

Move the cursor to the first entry whose key is greater than or equal to the input key. The entry returned by the previous entry() call will be invalid.

Parameters:

key - The input key

keyOffset - offset in the key buffer.

keyLen - key buffer length.

Returns:

true if we find an equal key; false otherwise.

Throws:

IOException - raised on errors performing I/O.

rewind

public void rewind()
            throws IOException

Rewind to the first entry in the scanner. The entry returned by the previous entry() call will be invalid.

Throws:

IOException - raised on errors performing I/O.

seekToEnd

public void seekToEnd()
               throws IOException

Seek to the end of the scanner. The entry returned by the previous entry() call will be invalid.

Throws:

IOException - raised on errors performing I/O.

lowerBound

public void lowerBound(byte[] key)
                throws IOException

Move the cursor to the first entry whose key is greater than or equal to the input key. Synonymous to lowerBound(key, 0, key.length). The entry returned by the previous entry() call will be invalid.

Parameters:

key - The input key

Throws:

IOException - raised on errors performing I/O.

lowerBound

public void lowerBound(byte[] key,
 int keyOffset,
 int keyLen)
                throws IOException

Move the cursor to the first entry whose key is greater than or equal to the input key. The entry returned by the previous entry() call will be invalid.

Parameters:

key - The input key

keyOffset - offset in the key buffer.

keyLen - key buffer length.

Throws:

IOException - raised on errors performing I/O.

upperBound

public void upperBound(byte[] key)
                throws IOException

Move the cursor to the first entry whose key is strictly greater than the input key. Synonymous to upperBound(key, 0, key.length). The entry returned by the previous entry() call will be invalid.

Parameters:

key - The input key

Throws:

IOException - raised on errors performing I/O.

upperBound

public void upperBound(byte[] key,
 int keyOffset,
 int keyLen)
                throws IOException

Move the cursor to the first entry whose key is strictly greater than the input key. The entry returned by the previous entry() call will be invalid.

Parameters:

key - The input key

keyOffset - offset in the key buffer.

keyLen - key buffer length.

Throws:

IOException - raised on errors performing I/O.

advance

public boolean advance()
                throws IOException

Move the cursor to the next key-value pair. The entry returned by the previous entry() call will be invalid.

Returns:

true if the cursor successfully moves. False when cursor is already at the end location and cannot be advanced.

Throws:

IOException - raised on errors performing I/O.

close

public void close()
           throws IOException

Close the scanner. Release all resources. The behavior of using the scanner after calling close is not defined. The entry returned by the previous entry() call will be invalid.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException

atEnd

public boolean atEnd()

Is cursor at the end location?

Returns:

true if the cursor is at the end location.

entry

public TFile.Reader.Scanner.Entry entry()
                                 throws IOException

Get an entry to access the key and value.

Returns:

The Entry object to access the key and value.

Throws:

IOException - raised on errors performing I/O.

getRecordNum

public long getRecordNum()
                  throws IOException

Get the RecordNum corresponding to the entry pointed by the cursor.

Returns:

The RecordNum corresponding to the entry pointed by the cursor.

Throws:

IOException - raised on errors performing I/O.