org.apache.hadoop.hbase.regionserver

Class ReversedMobStoreScanner

java.lang.Object

org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner

org.apache.hadoop.hbase.regionserver.NonReversedNonLazyKeyValueScanner

org.apache.hadoop.hbase.regionserver.StoreScanner

org.apache.hadoop.hbase.regionserver.ReversedMobStoreScanner

All Implemented Interfaces:

Closeable, AutoCloseable, ChangedReadersObserver, InternalScanner, KeyValueScanner

@InterfaceAudience.Private
public class ReversedMobStoreScanner
extends StoreScanner

ReversedMobStoreScanner extends from ReversedStoreScanner, and is used to support reversed scanning in both the memstore and the MOB store.

Field Summary

Fields

Modifier and Type	Field and Description
protected HMobStore	mobStore

Fields inherited from class org.apache.hadoop.hbase.regionserver.StoreScanner

cacheBlocks, cellsPerHeartbeatCheck, closing, columns, countPerRow, DEFAULT_HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK, executor, explicitColumnQuery, HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK, heap, isGet, isParallelSeekEnabled, lastTop, lazySeekEnabledGlobally, lock, matcher, maxRowSize, minVersions, now, oldestUnexpiredTS, readPt, scan, store, storeLimit, storeOffset, STORESCANNER_PARALLEL_SEEK_ENABLE, useRowColBloom

Method Summary

Modifier and Type	Method and Description
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
protected void	checkScanOrder(Cell prevKV, Cell kv, KeyValue.KVComparator comparator) Check whether scan as expected order
boolean	next(List<Cell> outResult, ScannerContext ctx) Firstly reads the cells from the HBase.
boolean	reseek(Cell kv) Reseek the scanner at or after the specified KeyValue.
protected void	resetKVHeap(List<? extends KeyValueScanner> scanners, KeyValue.KVComparator comparator)
boolean	seek(Cell key) Seek the scanner at or after the specified KeyValue.
protected boolean	seekAsDirection(Cell kv) Do a backwardSeek in a reversed StoreScanner(scan backward)
protected void	seekScanners(List<? extends KeyValueScanner> scanners, Cell seekKey, boolean isLazy, boolean isParallelSeek) Seek the specified scanners with the given key
protected boolean	seekToNextRow(Cell kv)
boolean	seekToPreviousRow(Cell key) Seek the scanner at the first Cell of the row which is the previous row of specified key

Methods inherited from class org.apache.hadoop.hbase.regionserver.StoreScanner

checkReseek, close, getEstimatedNumberOfKvsScanned, getNextIndexedKey, getScannersNoCompaction, getSequenceID, next, next, peek, resetScannerStack, selectScannersFrom, updateReaders

Methods inherited from class org.apache.hadoop.hbase.regionserver.NonReversedNonLazyKeyValueScanner

seekToLastRow

Methods inherited from class org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner

doRealSeek, enforceSeek, isFileScanner, realSeekDone, requestSeek, shouldUseScanner

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.hadoop.hbase.regionserver.KeyValueScanner

close, enforceSeek, getNextIndexedKey, getSequenceID, isFileScanner, next, peek, realSeekDone, requestSeek, seekToLastRow, shouldUseScanner

Field Detail

mobStore

protected final HMobStore mobStore

Method Detail

next

public boolean next(List<Cell> outResult,
                    ScannerContext ctx)
             throws IOException

Firstly reads the cells from the HBase. If the cell is a reference cell (which has the reference tag), the scanner need seek this cell from the mob file, and use the cell found from the mob file as the result.

Specified by:

next in interface InternalScanner

Overrides:

next in class StoreScanner

Parameters:

outResult - return output array

Returns:

true if there are more rows, false if scanner is done

Throws:

IOException - e

resetKVHeap

protected void resetKVHeap(List<? extends KeyValueScanner> scanners,
                           KeyValue.KVComparator comparator)
                    throws IOException

Overrides:

resetKVHeap in class StoreScanner

Throws:

IOException

seekScanners

protected void seekScanners(List<? extends KeyValueScanner> scanners,
                            Cell seekKey,
                            boolean isLazy,
                            boolean isParallelSeek)
                     throws IOException

Description copied from class: StoreScanner

Seek the specified scanners with the given key

Overrides:

seekScanners in class StoreScanner

isLazy - true if using lazy seek

isParallelSeek - true if using parallel seek

Throws:

IOException

seekToNextRow

protected boolean seekToNextRow(Cell kv)
                         throws IOException

Overrides:

seekToNextRow in class StoreScanner

Throws:

IOException

seekAsDirection

protected boolean seekAsDirection(Cell kv)
                           throws IOException

Do a backwardSeek in a reversed StoreScanner(scan backward)

Overrides:

seekAsDirection in class StoreScanner

Returns:

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

Throws:

IOException

checkScanOrder

protected void checkScanOrder(Cell prevKV,
                              Cell kv,
                              KeyValue.KVComparator comparator)
                       throws IOException

Description copied from class: StoreScanner

Check whether scan as expected order

Overrides:

checkScanOrder in class StoreScanner

Throws:

IOException

reseek

public boolean reseek(Cell kv)
               throws IOException

Description copied from interface: KeyValueScanner

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.

Specified by:

reseek in interface KeyValueScanner

Overrides:

reseek in class StoreScanner

Parameters:

kv - seek value (should be non-null)

Returns:

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

Throws:

IOException

seek

public boolean seek(Cell key)
             throws IOException

Description copied from interface: KeyValueScanner

Seek the scanner at or after the specified KeyValue.

Specified by:

seek in interface KeyValueScanner

Overrides:

seek in class StoreScanner

Parameters:

key - seek value

Returns:

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

Throws:

IOException

seekToPreviousRow

public boolean seekToPreviousRow(Cell key)
                          throws IOException

Description copied from interface: KeyValueScanner

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

Specified by:

seekToPreviousRow in interface KeyValueScanner

Overrides:

seekToPreviousRow in class NonReversedNonLazyKeyValueScanner

Parameters:

key - seek value

Returns:

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

Throws:

IOException

backwardSeek

public boolean backwardSeek(Cell key)
                     throws IOException

Description copied from interface: 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

Specified by:

backwardSeek in interface KeyValueScanner

Overrides:

backwardSeek in class NonReversedNonLazyKeyValueScanner

Parameters:

key - seek KeyValue

Returns:

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

Throws:

IOException