Package org.apache.hadoop.hbase.regionserver

Class StoreScanner

java.lang.Object

org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner

org.apache.hadoop.hbase.regionserver.NonReversedNonLazyKeyValueScanner

org.apache.hadoop.hbase.regionserver.StoreScanner

All Implemented Interfaces:

Closeable, AutoCloseable, ChangedReadersObserver, InternalScanner, KeyValueScanner, Shipper

Direct Known Subclasses:

MobStoreScanner, ReversedStoreScanner

@Private
public class StoreScanner
extends NonReversedNonLazyKeyValueScanner
implements KeyValueScanner, InternalScanner, ChangedReadersObserver

Scanner scans both the memstore and the Store. Coalesce KeyValue stream into List<KeyValue> for a single row.

The implementation is not thread safe. So there will be no race between next and close. The only exception is updateReaders, it will be called in the memstore flush thread to indicate that there is a flush.

Field Summary

Fields

Modifier and Type	Field	Description
private long	bytesRead
private boolean	cacheBlocks
private final long	cellsPerHeartbeatCheck
private final ReentrantLock	closeLock
private boolean	closing
private final CellComparator	comparator
private long	countPerRow
(package private) final List<KeyValueScanner>	currentScanners
static final long	DEFAULT_HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK	Default value of HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK.
private ExecutorService	executor
private final boolean	explicitColumnQuery
private boolean	flushed
private final List<KeyValueScanner>	flushedstoreFileScanners
private final ReentrantLock	flushLock
private final boolean	get
static final String	HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK	The number of cells scanned in between timeout checks.
protected KeyValueHeap	heap
private long	kvsScanned	The number of KVs seen by the scanner.
(package private) static final boolean	LAZY_SEEK_ENABLED_BY_DEFAULT	We don't ever expect to change this, the constant is just for clarity.
private static boolean	lazySeekEnabledGlobally	Used during unit testing to ensure that lazy seek does save seek ops
private static final org.slf4j.Logger	LOG
private ScanQueryMatcher	matcher
private final long	maxRowSize
(package private) long	memstoreOnlyReads
private final List<KeyValueScanner>	memStoreScannersAfterFlush
private final int	minVersions
(package private) long	mixedReads
private final long	now
private final long	oldestUnexpiredTS
private boolean	parallelSeekEnabled	A flag that enables StoreFileScanner parallel-seeking
private final long	preadMaxBytes
private ExtendedCell	prevCell
protected final long	readPt
private final Scan.ReadType	readType
private final Scan	scan
private static final Scan	SCAN_FOR_COMPACTION
private final List<KeyValueScanner>	scannersForDelayedClose
private boolean	scanUsePread
protected final HStore	store
private int	storeLimit
private int	storeOffset
static final String	STORESCANNER_PARALLEL_SEEK_ENABLE
static final String	STORESCANNER_PREAD_MAX_BYTES	If the read type is Scan.ReadType.DEFAULT, we will start with pread, and if the kvs we scanned reaches this limit, we will reopen the scanner with stream.
private boolean	topChanged
private final boolean	useRowColBloom

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

NO_NEXT_INDEXED_KEY

Constructor Summary

Constructors

Modifier	Constructor	Description
(package private)	StoreScanner(Scan scan, ScanInfo scanInfo, NavigableSet<byte[]> columns, List<? extends KeyValueScanner> scanners)
(package private)	StoreScanner(Scan scan, ScanInfo scanInfo, NavigableSet<byte[]> columns, List<? extends KeyValueScanner> scanners, ScanType scanType)
private	StoreScanner(HStore store, Scan scan, ScanInfo scanInfo, int numColumns, long readPt, boolean cacheBlocks, ScanType scanType)	An internal constructor.
	StoreScanner(HStore store, ScanInfo scanInfo, List<? extends KeyValueScanner> scanners, long smallestReadPoint, long earliestPutTs, byte[] dropDeletesFromRow, byte[] dropDeletesToRow)	Used for compactions that drop deletes from a limited range of rows.
	StoreScanner(HStore store, ScanInfo scanInfo, List<? extends KeyValueScanner> scanners, ScanType scanType, long smallestReadPoint, long earliestPutTs)	Used for store file compaction and memstore compaction.
private	StoreScanner(HStore store, ScanInfo scanInfo, List<? extends KeyValueScanner> scanners, ScanType scanType, long smallestReadPoint, long earliestPutTs, byte[] dropDeletesFromRow, byte[] dropDeletesToRow)
	StoreScanner(HStore store, ScanInfo scanInfo, Scan scan, NavigableSet<byte[]> columns, long readPt)	Opens a scanner across memstore, snapshot, and all StoreFiles.
(package private)	StoreScanner(ScanInfo scanInfo, int maxVersions, ScanType scanType, List<? extends KeyValueScanner> scanners)
	StoreScanner(ScanInfo scanInfo, ScanType scanType, List<? extends KeyValueScanner> scanners)

Method Summary

Modifier and Type	Method	Description
private void	addCurrentScanners(List<? extends KeyValueScanner> scanners)
protected final boolean	checkFlushed()
protected void	checkScanOrder(Cell prevKV, Cell kv, CellComparator comparator)	Check whether scan as expected order
private static void	clearAndClose(List<KeyValueScanner> scanners)
void	close()	Close the KeyValue scanner.
private void	close(boolean withDelayedScannersClose)
(package private) static void	enableLazySeekGlobally(boolean enable)
(package private) List<KeyValueScanner>	getAllScannersForTesting()	Used in testing.
long	getEstimatedNumberOfKvsScanned()	Returns The estimated number of KVs seen by this scanner (includes some skipped KVs).
ExtendedCell	getNextIndexedKey()
long	getReadPoint()	Returns the read point of the current scan
private static boolean	isOnlyLatestVersionScan(Scan scan)
(package private) boolean	isScanUsePread()
private ScannerContext.NextState	needToReturn(List<? super ExtendedCell> outResult)	If the top cell won't be flushed into disk, the new top cell may be changed after #reopenAfterFlush.
protected KeyValueHeap	newKVHeap(List<? extends KeyValueScanner> scanners, CellComparator comparator)
KeyValue	next()	Return the next Cell in this scanner, iterating the scanner
boolean	next(List<? super ExtendedCell> outResult, ScannerContext scannerContext)	Get the next row of values from this Store.
private void	parallelSeek(List<? extends KeyValueScanner> scanners, ExtendedCell kv)	Seek storefiles in parallel to optimize IO latency as much as possible
ExtendedCell	peek()	Look at the next Cell in this scanner, but do not iterate scanner.
protected final boolean	reopenAfterFlush()	Returns if top of heap has changed (and KeyValueHeap has to try the next KV)
boolean	reseek(ExtendedCell kv)	Reseek the scanner at or after the specified KeyValue.
protected void	resetKVHeap(List<? extends KeyValueScanner> scanners, CellComparator comparator)
private void	resetQueryMatcher(ExtendedCell lastTopKey)
boolean	seek(ExtendedCell key)	Seek the scanner at or after the specified KeyValue.
private void	seekAllScanner(ScanInfo scanInfo, List<? extends KeyValueScanner> scanners)
protected boolean	seekAsDirection(ExtendedCell kv)	Do a reseek in a normal StoreScanner(scan forward)
private void	seekOrSkipToNextColumn(ExtendedCell cell)
private void	seekOrSkipToNextRow(ExtendedCell cell)
protected void	seekScanners(List<? extends KeyValueScanner> scanners, ExtendedCell seekKey, boolean isLazy, boolean isParallelSeek)	Seek the specified scanners with the given key
protected boolean	seekToNextRow(ExtendedCell c)
protected List<KeyValueScanner>	selectScannersFrom(HStore store, List<? extends KeyValueScanner> allScanners)	Filters the given list of scanners using Bloom filter, time range, and TTL.
void	shipped()	Called after a batch of rows scanned and set to be returned to client.
protected boolean	trySkipToNextColumn(ExtendedCell cell)	See trySkipToNextRow(ExtendedCell)
protected boolean	trySkipToNextRow(ExtendedCell cell)	See if we should actually SEEK or rather just SKIP to the next Cell (see HBASE-13109).
(package private) void	trySwitchToStreamRead()
private void	updateMetricsStore(boolean memstoreRead)
void	updateReaders(List<HStoreFile> sfs, List<KeyValueScanner> memStoreScanners)	Notify observers.

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

backwardSeek, seekToLastRow, seekToPreviousRow

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

doRealSeek, enforceSeek, getFilePath, isFileScanner, realSeekDone, recordBlockSize, 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.InternalScanner

next

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

backwardSeek, enforceSeek, getFilePath, getScannerOrder, isFileScanner, realSeekDone, recordBlockSize, requestSeek, seekToLastRow, seekToPreviousRow, shouldUseScanner

Field Details

LOG

private static final org.slf4j.Logger LOG

store

protected final HStore store

comparator

private final CellComparator comparator

matcher

private ScanQueryMatcher matcher

heap

protected KeyValueHeap heap

cacheBlocks

private boolean cacheBlocks

countPerRow

private long countPerRow

storeLimit

private int storeLimit

storeOffset

private int storeOffset

closing

private volatile boolean closing

get

private final boolean get

explicitColumnQuery

private final boolean explicitColumnQuery

useRowColBloom

private final boolean useRowColBloom

parallelSeekEnabled

private boolean parallelSeekEnabled

A flag that enables StoreFileScanner parallel-seeking

executor

private ExecutorService executor

scan

private final Scan scan

oldestUnexpiredTS

private final long oldestUnexpiredTS

now

private final long now

minVersions

private final int minVersions

maxRowSize

private final long maxRowSize

cellsPerHeartbeatCheck

private final long cellsPerHeartbeatCheck

memstoreOnlyReads

long memstoreOnlyReads

mixedReads

long mixedReads

scannersForDelayedClose

private final List<KeyValueScanner> scannersForDelayedClose

kvsScanned

private long kvsScanned

The number of KVs seen by the scanner. Includes explicitly skipped KVs, but not KVs skipped via seeking to next row/column. TODO: estimate them?

prevCell

private ExtendedCell prevCell

preadMaxBytes

private final long preadMaxBytes

bytesRead

private long bytesRead

LAZY_SEEK_ENABLED_BY_DEFAULT

static final boolean LAZY_SEEK_ENABLED_BY_DEFAULT

We don't ever expect to change this, the constant is just for clarity.

See Also:

• Constant Field Values

STORESCANNER_PARALLEL_SEEK_ENABLE

public static final String STORESCANNER_PARALLEL_SEEK_ENABLE

See Also:

• Constant Field Values

lazySeekEnabledGlobally

private static boolean lazySeekEnabledGlobally

Used during unit testing to ensure that lazy seek does save seek ops

HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK

public static final String HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK

The number of cells scanned in between timeout checks. Specifying a larger value means that timeout checks will occur less frequently. Specifying a small value will lead to more frequent timeout checks.

See Also:

• Constant Field Values

DEFAULT_HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK

public static final long DEFAULT_HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK

Default value of HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK.

See Also:

• Constant Field Values

STORESCANNER_PREAD_MAX_BYTES

public static final String STORESCANNER_PREAD_MAX_BYTES

If the read type is Scan.ReadType.DEFAULT, we will start with pread, and if the kvs we scanned reaches this limit, we will reopen the scanner with stream. The default value is 4 times of block size for this store. If configured with a value <0, for all scans with ReadType DEFAULT, we will open scanner with stream mode itself.

See Also:

• Constant Field Values

readType

private final Scan.ReadType readType

scanUsePread

private boolean scanUsePread

flushed

private volatile boolean flushed

flushedstoreFileScanners

private final List<KeyValueScanner> flushedstoreFileScanners

memStoreScannersAfterFlush

private final List<KeyValueScanner> memStoreScannersAfterFlush

currentScanners

final List<KeyValueScanner> currentScanners

flushLock

private final ReentrantLock flushLock

closeLock

private final ReentrantLock closeLock

readPt

protected final long readPt

topChanged

private boolean topChanged

SCAN_FOR_COMPACTION

private static final Scan SCAN_FOR_COMPACTION

Constructor Details

StoreScanner

private StoreScanner(HStore store,
 Scan scan,
 ScanInfo scanInfo,
 int numColumns,
 long readPt,
 boolean cacheBlocks,
 ScanType scanType)

An internal constructor.

StoreScanner

public StoreScanner(HStore store,
 ScanInfo scanInfo,
 Scan scan,
 NavigableSet<byte[]> columns,
 long readPt)
             throws IOException

Opens a scanner across memstore, snapshot, and all StoreFiles. Assumes we are not in a compaction.

Parameters:

store - who we scan

scan - the spec

columns - which columns we are scanning

Throws:

IOException

StoreScanner

public StoreScanner(HStore store,
 ScanInfo scanInfo,
 List<? extends KeyValueScanner> scanners,
 ScanType scanType,
 long smallestReadPoint,
 long earliestPutTs)
             throws IOException

Used for store file compaction and memstore compaction.

Opens a scanner across specified StoreFiles/MemStoreSegments.

Parameters:

store - who we scan

scanners - ancillary scanners

smallestReadPoint - the readPoint that we should use for tracking versions

Throws:

IOException

StoreScanner

public StoreScanner(HStore store,
 ScanInfo scanInfo,
 List<? extends KeyValueScanner> scanners,
 long smallestReadPoint,
 long earliestPutTs,
 byte[] dropDeletesFromRow,
 byte[] dropDeletesToRow)
             throws IOException

Used for compactions that drop deletes from a limited range of rows.

Opens a scanner across specified StoreFiles.

Parameters:

store - who we scan

scanners - ancillary scanners

smallestReadPoint - the readPoint that we should use for tracking versions

dropDeletesFromRow - The inclusive left bound of the range; can be EMPTY_START_ROW.

dropDeletesToRow - The exclusive right bound of the range; can be EMPTY_END_ROW.

Throws:

IOException

StoreScanner

private StoreScanner(HStore store,
 ScanInfo scanInfo,
 List<? extends KeyValueScanner> scanners,
 ScanType scanType,
 long smallestReadPoint,
 long earliestPutTs,
 byte[] dropDeletesFromRow,
 byte[] dropDeletesToRow)
              throws IOException

Throws:

IOException

StoreScanner

public StoreScanner(ScanInfo scanInfo,
 ScanType scanType,
 List<? extends KeyValueScanner> scanners)
             throws IOException

Throws:

IOException

StoreScanner

StoreScanner(Scan scan,
 ScanInfo scanInfo,
 NavigableSet<byte[]> columns,
 List<? extends KeyValueScanner> scanners,
 ScanType scanType)
      throws IOException

Throws:

IOException

StoreScanner

StoreScanner(Scan scan,
 ScanInfo scanInfo,
 NavigableSet<byte[]> columns,
 List<? extends KeyValueScanner> scanners)
      throws IOException

Throws:

IOException

StoreScanner

StoreScanner(ScanInfo scanInfo,
 int maxVersions,
 ScanType scanType,
 List<? extends KeyValueScanner> scanners)
      throws IOException

Throws:

IOException

Method Details

addCurrentScanners

private void addCurrentScanners(List<? extends KeyValueScanner> scanners)

isOnlyLatestVersionScan

private static boolean isOnlyLatestVersionScan(Scan scan)

seekAllScanner

private void seekAllScanner(ScanInfo scanInfo,
 List<? extends KeyValueScanner> scanners)
                     throws IOException

Throws:

IOException

isScanUsePread

boolean isScanUsePread()

seekScanners

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

Seek the specified scanners with the given key

Parameters:

isLazy - true if using lazy seek

isParallelSeek - true if using parallel seek

Throws:

IOException

resetKVHeap

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

Throws:

IOException

newKVHeap

protected KeyValueHeap newKVHeap(List<? extends KeyValueScanner> scanners,
 CellComparator comparator)
                          throws IOException

Throws:

IOException

selectScannersFrom

protected List<KeyValueScanner> selectScannersFrom(HStore store,
 List<? extends KeyValueScanner> allScanners)

Filters the given list of scanners using Bloom filter, time range, and TTL.

Will be overridden by testcase so declared as protected.

peek

public ExtendedCell peek()

Description copied from interface: KeyValueScanner

Look at the next Cell in this scanner, but do not iterate scanner. NOTICE: The returned cell has not been passed into ScanQueryMatcher. So it may not be what the user need.

Specified by:

peek in interface KeyValueScanner

Returns:

the next Cell

next

public KeyValue next()

Description copied from interface: KeyValueScanner

Return the next Cell in this scanner, iterating the scanner

Specified by:

next in interface KeyValueScanner

Returns:

the next Cell

close

public void close()

Description copied from interface: KeyValueScanner

Close the KeyValue scanner.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface InternalScanner

Specified by:

close in interface KeyValueScanner

close

private void close(boolean withDelayedScannersClose)

seek

public boolean seek(ExtendedCell key)
             throws IOException

Description copied from interface: KeyValueScanner

Seek the scanner at or after the specified KeyValue.

Specified by:

seek in interface KeyValueScanner

Parameters:

key - seek value

Returns:

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

Throws:

IOException

next

public boolean next(List<? super ExtendedCell> outResult,
 ScannerContext scannerContext)
             throws IOException

Get the next row of values from this Store.

Specified by:

next in interface InternalScanner

Parameters:

outResult - return output array. We will only add ExtendedCell to this list, but for CP users, you'd better just use RawCell as ExtendedCell is IA.Private.

Returns:

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

Throws:

IOException

updateMetricsStore

private void updateMetricsStore(boolean memstoreRead)

needToReturn

private ScannerContext.NextState needToReturn(List<? super ExtendedCell> outResult)

If the top cell won't be flushed into disk, the new top cell may be changed after #reopenAfterFlush. Because the older top cell only exist in the memstore scanner but the memstore scanner is replaced by hfile scanner after #reopenAfterFlush. If the row of top cell is changed, we should return the current cells. Otherwise, we may return the cells across different rows.

Parameters:

outResult - the cells which are visible for user scan

Returns:

null is the top cell doesn't change. Otherwise, the NextState to return

seekOrSkipToNextRow

private void seekOrSkipToNextRow(ExtendedCell cell)
                          throws IOException

Throws:

IOException

seekOrSkipToNextColumn

private void seekOrSkipToNextColumn(ExtendedCell cell)
                             throws IOException

Throws:

IOException

trySkipToNextRow

protected boolean trySkipToNextRow(ExtendedCell cell)
                            throws IOException

See if we should actually SEEK or rather just SKIP to the next Cell (see HBASE-13109). ScanQueryMatcher may issue SEEK hints, such as seek to next column, next row, or seek to an arbitrary seek key. This method decides whether a seek is the most efficient _actual_ way to get us to the requested cell (SEEKs are more expensive than SKIP, SKIP, SKIP inside the current, loaded block). It does this by looking at the next indexed key of the current HFile. This key is then compared with the _SEEK_ key, where a SEEK key is an artificial 'last possible key on the row' (only in here, we avoid actually creating a SEEK key; in the compare we work with the current Cell but compare as though it were a seek key; see down in matcher.compareKeyForNextRow, etc). If the compare gets us onto the next block we *_SEEK, otherwise we just SKIP to the next requested cell.

Other notes:

• Rows can straddle block boundaries
• Versions of columns can straddle block boundaries (i.e. column C1 at T1 might be in a different block than column C1 at T2)
• We want to SKIP if the chance is high that we'll find the desired Cell after a few SKIPs...
• We want to SEEK when the chance is high that we'll be able to seek past many Cells, especially if we know we need to go to the next block.

A good proxy (best effort) to determine whether SKIP is better than SEEK is whether we'll likely end up seeking to the next block (or past the next block) to get our next column. Example:

 |    BLOCK 1              |     BLOCK 2                   |
 |  r1/c1, r1/c2, r1/c3    |    r1/c4, r1/c5, r2/c1        |
                                   ^         ^
                                   |         |
                           Next Index Key   SEEK_NEXT_ROW (before r2/c1)


 |    BLOCK 1                       |     BLOCK 2                      |
 |  r1/c1/t5, r1/c1/t4, r1/c1/t3    |    r1/c1/t2, r1/c1/T1, r1/c2/T3  |
                                            ^              ^
                                            |              |
                                    Next Index Key        SEEK_NEXT_COL
 

Now imagine we want columns c1 and c3 (see first diagram above), the 'Next Index Key' of r1/c4 is > r1/c3 so we should seek to get to the c1 on the next row, r2. In second case, say we only want one version of c1, after we have it, a SEEK_COL will be issued to get to c2. Looking at the 'Next Index Key', it would land us in the next block, so we should SEEK. In other scenarios where the SEEK will not land us in the next block, it is very likely better to issues a series of SKIPs.

Parameters:

cell - current cell

Returns:

true means skip to next row, false means not

Throws:

IOException

trySkipToNextColumn

protected boolean trySkipToNextColumn(ExtendedCell cell)
                               throws IOException

See trySkipToNextRow(ExtendedCell)

Parameters:

cell - current cell

Returns:

true means skip to next column, false means not

Throws:

IOException

getReadPoint

public long getReadPoint()

Description copied from interface: ChangedReadersObserver

Returns the read point of the current scan

Specified by:

getReadPoint in interface ChangedReadersObserver

clearAndClose

private static void clearAndClose(List<KeyValueScanner> scanners)

updateReaders

public void updateReaders(List<HStoreFile> sfs,
 List<KeyValueScanner> memStoreScanners)
                   throws IOException

Description copied from interface: ChangedReadersObserver

Notify observers.
NOTE:Before we invoke this method,HStoreFile.increaseRefCount() is invoked for every HStoreFile in 'sfs' input parameter to prevent HStoreFile is archived after a concurrent compaction, and after this method is invoked,HStoreFile.decreaseRefCount() is invoked.So if you open the StoreFileReader or StoreFileScanner asynchronously in this method,you may need to invoke HStoreFile.increaseRefCount() or HStoreFile.decreaseRefCount() by yourself to prevent the HStoreFiles be archived.

Specified by:

updateReaders in interface ChangedReadersObserver

Parameters:

sfs - The new files

memStoreScanners - scanner of current memstore

Throws:

IOException - e

reopenAfterFlush

protected final boolean reopenAfterFlush()
                                  throws IOException

Returns if top of heap has changed (and KeyValueHeap has to try the next KV)

Throws:

IOException

resetQueryMatcher

private void resetQueryMatcher(ExtendedCell lastTopKey)

checkScanOrder

protected void checkScanOrder(Cell prevKV,
 Cell kv,
 CellComparator comparator)
                       throws IOException

Check whether scan as expected order

Throws:

IOException

seekToNextRow

protected boolean seekToNextRow(ExtendedCell c)
                         throws IOException

Throws:

IOException

seekAsDirection

protected boolean seekAsDirection(ExtendedCell kv)
                           throws IOException

Do a reseek in a normal StoreScanner(scan forward)

Returns:

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

Throws:

IOException

reseek

public boolean reseek(ExtendedCell 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

Parameters:

kv - seek value (should be non-null)

Returns:

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

Throws:

IOException

trySwitchToStreamRead

void trySwitchToStreamRead()

checkFlushed

protected final boolean checkFlushed()

parallelSeek

private void parallelSeek(List<? extends KeyValueScanner> scanners,
 ExtendedCell kv)
                   throws IOException

Seek storefiles in parallel to optimize IO latency as much as possible

Parameters:

scanners - the list KeyValueScanners to be read from

kv - the KeyValue on which the operation is being requested

Throws:

IOException

getAllScannersForTesting

List<KeyValueScanner> getAllScannersForTesting()

Used in testing.

Returns:

all scanners in no particular order

enableLazySeekGlobally

static void enableLazySeekGlobally(boolean enable)

getEstimatedNumberOfKvsScanned

public long getEstimatedNumberOfKvsScanned()

Returns The estimated number of KVs seen by this scanner (includes some skipped KVs).

getNextIndexedKey

public ExtendedCell getNextIndexedKey()

Specified by:

getNextIndexedKey in interface KeyValueScanner

Overrides:

getNextIndexedKey in class NonLazyKeyValueScanner

Returns:

the next key in the index, usually the first key of next block OR a key that falls between last key of current block and first key of next block.. see HFileWriterImpl#getMidpoint, or null if not known.

shipped

public void shipped()
             throws IOException

Description copied from interface: Shipper

Called after a batch of rows scanned and set to be returned to client. Any in between cleanup can be done here.

Specified by:

shipped in interface Shipper

Overrides:

shipped in class NonLazyKeyValueScanner

Throws:

IOException