org.apache.hadoop.hbase.regionserver

类 SegmentScanner

java.lang.Object

org.apache.hadoop.hbase.regionserver.SegmentScanner

所有已实现的接口:

Closeable, AutoCloseable, KeyValueScanner, Shipper

@InterfaceAudience.Private
public class SegmentScanner
extends Object
implements KeyValueScanner

A scanner of a single memstore segment.

字段概要

字段

限定符和类型	字段和说明
protected boolean	closed
protected Cell	current
protected Iterator<Cell>	iter
protected Segment	segment

从接口继承的字段 org.apache.hadoop.hbase.regionserver.KeyValueScanner

NO_NEXT_INDEXED_KEY

构造器概要

构造器

限定符	构造器和说明
protected	SegmentScanner(Segment segment, long readPoint) Scanners are ordered from 0 (oldest) to newest in increasing order.

方法概要

限定符和类型	方法和说明
boolean	backwardSeek(Cell key) Seek the scanner at or before the row of specified Cell, it firstly tries to seek the scanner at or after the specified Cell, return if peek KeyValue of scanner has the same row with specified Cell, otherwise seek the scanner at the first Cell of the row which is the previous row of specified KeyValue
void	close() Close the KeyValue scanner.
void	enforceSeek() This function should be never called on scanners that always do real seek operations (i.e. most of the scanners and also this one).
org.apache.hadoop.fs.Path	getFilePath()
protected Iterator<Cell>	getIterator(Cell cell)
Cell	getNextIndexedKey()
boolean	isFileScanner()
Cell	next() Return the next Cell in this scanner, iterating the scanner
Cell	peek() Look at the next Cell in this scanner, but do not iterate the scanner
boolean	realSeekDone() This scanner is working solely on the in-memory MemStore and doesn't work on store files, MutableCellSetSegmentScanner always does the seek, therefore always returning true.
boolean	requestSeek(Cell c, boolean forward, boolean useBloom) Similar to KeyValueScanner.seek(org.apache.hadoop.hbase.Cell) (or KeyValueScanner.reseek(org.apache.hadoop.hbase.Cell) if forward is true) but only does a seek operation after checking that it is really necessary for the row/column combination specified by the kv parameter.
boolean	reseek(Cell cell) Reseek the scanner at or after the specified KeyValue.
boolean	seek(Cell cell) Seek the scanner at or after the specified Cell.
boolean	seekToLastRow() Seek the scanner at the first KeyValue of last row
boolean	seekToPreviousRow(Cell cell) Seek the scanner at the first Cell of the row which is the previous row of specified key
void	shipped() Called after a batch of rows scanned (RPC) and set to be returned to client.
boolean	shouldUseScanner(Scan scan, HStore store, long oldestUnexpiredTS) This functionality should be resolved in the higher level which is MemStoreScanner, currently returns true as default.
String	toString()
protected void	updateCurrent() Private internal method for iterating over the segment, skipping the cells with irrelevant MVCC

从类继承的方法 java.lang.Object

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

从接口继承的方法 org.apache.hadoop.hbase.regionserver.KeyValueScanner

getScannerOrder

字段详细资料

segment

protected final Segment segment

iter

protected Iterator<Cell> iter

current

protected Cell current

closed

protected boolean closed

构造器详细资料

SegmentScanner

protected SegmentScanner(Segment segment,
                         long readPoint)

Scanners are ordered from 0 (oldest) to newest in increasing order.

方法详细资料

peek

public Cell peek()

Look at the next Cell in this scanner, but do not iterate the scanner

指定者:

peek 在接口中 KeyValueScanner

返回:

the currently observed Cell

next

public Cell next()
          throws IOException

Return the next Cell in this scanner, iterating the scanner

指定者:

next 在接口中 KeyValueScanner

返回:

the next Cell or null if end of scanner

抛出:

IOException

seek

public boolean seek(Cell cell)
             throws IOException

Seek the scanner at or after the specified Cell.

指定者:

seek 在接口中 KeyValueScanner

参数:

cell - seek value

返回:

true if scanner has values left, false if end of scanner

抛出:

IOException

getIterator

protected Iterator<Cell> getIterator(Cell cell)

reseek

public boolean reseek(Cell cell)
               throws IOException

Reseek the scanner at or after the specified KeyValue. This method is guaranteed to seek at or after the required key only if the key comes after the current position of the scanner. Should not be used to seek to a key which may come before the current position.

指定者:

reseek 在接口中 KeyValueScanner

参数:

cell - seek value (should be non-null)

返回:

true if scanner has values left, false if end of scanner

抛出:

IOException

backwardSeek

public boolean backwardSeek(Cell key)
                     throws IOException

Seek the scanner at or before the row of specified Cell, it firstly tries to seek the scanner at or after the specified Cell, return if peek KeyValue of scanner has the same row with specified Cell, otherwise seek the scanner at the first Cell of the row which is the previous row of specified KeyValue

指定者:

backwardSeek 在接口中 KeyValueScanner

参数:

key - seek Cell

返回:

true if the scanner is at the valid KeyValue, false if such Cell does not exist

抛出:

IOException

seekToPreviousRow

public boolean seekToPreviousRow(Cell cell)
                          throws IOException

Seek the scanner at the first Cell of the row which is the previous row of specified key

指定者:

seekToPreviousRow 在接口中 KeyValueScanner

参数:

cell - seek value

返回:

true if the scanner at the first valid Cell of previous row, false if not existing such Cell

抛出:

IOException

seekToLastRow

public boolean seekToLastRow()
                      throws IOException

Seek the scanner at the first KeyValue of last row

指定者:

seekToLastRow 在接口中 KeyValueScanner

返回:

true if scanner has values left, false if the underlying data is empty

抛出:

IOException

close

public void close()

Close the KeyValue scanner.

指定者:

close 在接口中 Closeable

指定者:

close 在接口中 AutoCloseable

指定者:

close 在接口中 KeyValueScanner

shouldUseScanner

public boolean shouldUseScanner(Scan scan,
                                HStore store,
                                long oldestUnexpiredTS)

This functionality should be resolved in the higher level which is MemStoreScanner, currently returns true as default. Doesn't throw IllegalStateException in order not to change the signature of the overridden method

指定者:

shouldUseScanner 在接口中 KeyValueScanner

参数:

scan - the scan that we are selecting scanners for

store - the store we are performing the scan on.

oldestUnexpiredTS - the oldest timestamp we are interested in for this query, based on TTL

返回:

true if the scanner should be included in the query

requestSeek

public boolean requestSeek(Cell c,
                           boolean forward,
                           boolean useBloom)
                    throws IOException

从接口复制的说明: KeyValueScanner

Similar to KeyValueScanner.seek(org.apache.hadoop.hbase.Cell) (or KeyValueScanner.reseek(org.apache.hadoop.hbase.Cell) if forward is true) but only does a seek operation after checking that it is really necessary for the row/column combination specified by the kv parameter. This function was added to avoid unnecessary disk seeks by checking row-column Bloom filters before a seek on multi-column get/scan queries, and to optimize by looking up more recent files first.

指定者:

requestSeek 在接口中 KeyValueScanner

forward - do a forward-only "reseek" instead of a random-access seek

useBloom - whether to enable multi-column Bloom filter optimization

抛出:

IOException

realSeekDone

public boolean realSeekDone()

This scanner is working solely on the in-memory MemStore and doesn't work on store files, MutableCellSetSegmentScanner always does the seek, therefore always returning true.

指定者:

realSeekDone 在接口中 KeyValueScanner

enforceSeek

public void enforceSeek()
                 throws IOException

This function should be never called on scanners that always do real seek operations (i.e. most of the scanners and also this one). The easiest way to achieve this is to call realSeekDone() first.

指定者:

enforceSeek 在接口中 KeyValueScanner

抛出:

IOException

isFileScanner

public boolean isFileScanner()

指定者:

isFileScanner 在接口中 KeyValueScanner

返回:

true if this is a file scanner. Otherwise a memory scanner is assumed.

getFilePath

public org.apache.hadoop.fs.Path getFilePath()

指定者:

getFilePath 在接口中 KeyValueScanner

返回:

the file path if this is a file scanner, otherwise null.

另请参阅:

KeyValueScanner.isFileScanner()

getNextIndexedKey

public Cell getNextIndexedKey()

指定者:

getNextIndexedKey 在接口中 KeyValueScanner

返回:

the next key in the index (the key to seek to the next block) if known, or null otherwise Not relevant for in-memory scanner

shipped

public void shipped()
             throws IOException

Called after a batch of rows scanned (RPC) and set to be returned to client. Any in between cleanup can be done here. Nothing to be done for MutableCellSetSegmentScanner.

指定者:

shipped 在接口中 Shipper

抛出:

IOException

toString

public String toString()

覆盖:

toString 在类中 Object

updateCurrent

protected void updateCurrent()

Private internal method for iterating over the segment, skipping the cells with irrelevant MVCC