org.apache.hadoop.hbase.regionserver

类 ReversedKeyValueHeap

java.lang.Object

org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner

org.apache.hadoop.hbase.regionserver.NonReversedNonLazyKeyValueScanner

org.apache.hadoop.hbase.regionserver.KeyValueHeap

org.apache.hadoop.hbase.regionserver.ReversedKeyValueHeap

所有已实现的接口:

Closeable, AutoCloseable, InternalScanner, KeyValueScanner, Shipper

@InterfaceAudience.Private
public class ReversedKeyValueHeap
extends KeyValueHeap

ReversedKeyValueHeap is used for supporting reversed scanning. Compared with KeyValueHeap, its scanner comparator is a little different (see ReversedKVScannerComparator), all seek is backward seek(see KeyValueScanner.backwardSeek(org.apache.hadoop.hbase.Cell)), and it will jump to the previous row if it is already at the end of one row when calling next().

嵌套类概要

从类继承的嵌套类/接口 org.apache.hadoop.hbase.regionserver.KeyValueHeap

KeyValueHeap.KVScannerComparator

字段概要

从类继承的字段 org.apache.hadoop.hbase.regionserver.KeyValueHeap

comparator, current, heap, scannersForDelayedClose

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

构造器和说明
ReversedKeyValueHeap(List<? extends KeyValueScanner> scanners, CellComparator comparator)

方法概要

限定符和类型	方法和说明
boolean	backwardSeek(Cell seekKey) 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
Cell	next() Return the next Cell in this scanner, iterating the scanner
boolean	requestSeek(Cell key, 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 seekKey) This function is identical to the KeyValueHeap.seek(Cell) function except that scanner.seek(seekKey) is changed to scanner.reseek(seekKey).
boolean	seek(Cell seekKey) Seeks all scanners at or below the specified seek key.
boolean	seekToLastRow() Seek the scanner at the first KeyValue of last row
boolean	seekToPreviousRow(Cell seekKey) Seek the scanner at the first Cell of the row which is the previous row of specified key

从类继承的方法 org.apache.hadoop.hbase.regionserver.KeyValueHeap

close, getHeap, getNextIndexedKey, next, peek, pollRealKV, shipped

从类继承的方法 org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner

doRealSeek, enforceSeek, getFilePath, isFileScanner, realSeekDone, shouldUseScanner

从类继承的方法 java.lang.Object

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

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

enforceSeek, getFilePath, getScannerOrder, isFileScanner, realSeekDone, shouldUseScanner

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

next

构造器详细资料

ReversedKeyValueHeap

public ReversedKeyValueHeap(List<? extends KeyValueScanner> scanners,
                            CellComparator comparator)
                     throws IOException

参数:

scanners -

comparator -

抛出:

IOException

方法详细资料

seek

public boolean seek(Cell seekKey)
             throws IOException

从类复制的说明: KeyValueHeap

Seeks all scanners at or below the specified seek key. If we earlied-out of a row, we may end up skipping values that were never reached yet. Rather than iterating down, we want to give the opportunity to re-seek.

As individual scanners may run past their ends, those scanners are automatically closed and removed from the heap.

This function (and KeyValueHeap.reseek(Cell)) does not do multi-column Bloom filter and lazy-seek optimizations. To enable those, call KeyValueHeap.requestSeek(Cell, boolean, boolean).

指定者:

seek 在接口中 KeyValueScanner

覆盖:

seek 在类中 KeyValueHeap

参数:

seekKey - KeyValue to seek at or after

返回:

true if KeyValues exist at or after specified key, false if not

抛出:

IOException

reseek

public boolean reseek(Cell seekKey)
               throws IOException

从类复制的说明: KeyValueHeap

This function is identical to the KeyValueHeap.seek(Cell) function except that scanner.seek(seekKey) is changed to scanner.reseek(seekKey).

指定者:

reseek 在接口中 KeyValueScanner

覆盖:

reseek 在类中 KeyValueHeap

参数:

seekKey - seek value (should be non-null)

返回:

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

抛出:

IOException

requestSeek

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

从类复制的说明: KeyValueHeap

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

覆盖:

requestSeek 在类中 KeyValueHeap

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

useBloom - whether to enable multi-column Bloom filter optimization

抛出:

IOException

seekToPreviousRow

public boolean seekToPreviousRow(Cell seekKey)
                          throws IOException

从接口复制的说明: KeyValueScanner

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

覆盖:

seekToPreviousRow 在类中 NonReversedNonLazyKeyValueScanner

参数:

seekKey - 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

backwardSeek

public boolean backwardSeek(Cell seekKey)
                     throws IOException

从接口复制的说明: KeyValueScanner

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

覆盖:

backwardSeek 在类中 NonReversedNonLazyKeyValueScanner

参数:

seekKey - seek KeyValue

返回:

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

抛出:

IOException

next

public Cell next()
          throws IOException

从接口复制的说明: KeyValueScanner

Return the next Cell in this scanner, iterating the scanner

指定者:

next 在接口中 KeyValueScanner

覆盖:

next 在类中 KeyValueHeap

返回:

the next Cell

抛出:

IOException

seekToLastRow

public boolean seekToLastRow()
                      throws IOException

从接口复制的说明: KeyValueScanner

Seek the scanner at the first KeyValue of last row

指定者:

seekToLastRow 在接口中 KeyValueScanner

覆盖:

seekToLastRow 在类中 NonReversedNonLazyKeyValueScanner

返回:

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

抛出:

IOException