org.apache.hadoop.hbase.regionserver

类 KeyValueHeap

java.lang.Object

org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner

org.apache.hadoop.hbase.regionserver.NonReversedNonLazyKeyValueScanner

org.apache.hadoop.hbase.regionserver.KeyValueHeap

所有已实现的接口:

Closeable, AutoCloseable, InternalScanner, KeyValueScanner

直接已知子类:

ReversedKeyValueHeap

@InterfaceAudience.Private
public class KeyValueHeap
extends NonReversedNonLazyKeyValueScanner
implements KeyValueScanner, InternalScanner

Implements a heap merge across any number of KeyValueScanners.

Implements KeyValueScanner itself.

This class is used at the Region level to merge across Stores and at the Store level to merge across the memstore and StoreFiles.

In the Region case, we also need InternalScanner.next(List), so this class also implements InternalScanner. WARNING: As is, if you try to use this as an InternalScanner at the Store level, you will get runtime exceptions.

嵌套类概要

嵌套类

限定符和类型	类和说明
protected static class	KeyValueHeap.KVScannerComparator

字段概要

字段

限定符和类型	字段和说明
protected KeyValueHeap.KVScannerComparator	comparator
protected KeyValueScanner	current The current sub-scanner, i.e. the one that contains the next key/value to return to the client.
protected PriorityQueue<KeyValueScanner>	heap

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
KeyValueHeap(List<? extends KeyValueScanner> scanners, KeyValue.KVComparator comparator) Constructor.

方法概要

方法

限定符和类型	方法和说明
void	close() Close the KeyValue scanner.
PriorityQueue<KeyValueScanner>	getHeap()
Cell	getNextIndexedKey()
long	getScannerOrder() Get the order of this KeyValueScanner.
Cell	next() Return the next Cell in this scanner, iterating the scanner
boolean	next(List<Cell> result) Gets the next row of keys from the top-most scanner.
boolean	next(List<Cell> result, ScannerContext scannerContext) Grab the next row's worth of values.
Cell	peek() Look at the next Cell in this scanner, but do not iterate scanner.
protected KeyValueScanner	pollRealKV() Fetches the top sub-scanner from the priority queue, ensuring that a real seek has been done on it.
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 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.

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

backwardSeek, seekToLastRow, seekToPreviousRow

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

doRealSeek, enforceSeek, 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

backwardSeek, enforceSeek, isFileScanner, realSeekDone, seekToLastRow, seekToPreviousRow, shouldUseScanner

字段详细资料

heap

protected PriorityQueue<KeyValueScanner> heap

current

protected KeyValueScanner current

The current sub-scanner, i.e. the one that contains the next key/value to return to the client. This scanner is NOT included in heap (but we frequently add it back to the heap and pull the new winner out). We maintain an invariant that the current sub-scanner has already done a real seek, and that current.peek() is always a real key/value (or null) except for the fake last-key-on-row-column supplied by the multi-column Bloom filter optimization, which is OK to propagate to StoreScanner. In order to ensure that, always use pollRealKV() to update current.

comparator

protected KeyValueHeap.KVScannerComparator comparator

构造器详细资料

KeyValueHeap

public KeyValueHeap(List<? extends KeyValueScanner> scanners,
            KeyValue.KVComparator comparator)
             throws IOException

Constructor. This KeyValueHeap will handle closing of passed in KeyValueScanners.

参数:

scanners -

comparator -

抛出:

IOException

方法详细资料

peek

public Cell peek()

从接口复制的说明: 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.

指定者:

peek 在接口中 KeyValueScanner

返回:

the next Cell

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

返回:

the next Cell

抛出:

IOException

next

public boolean next(List<Cell> result)
             throws IOException

Gets the next row of keys from the top-most scanner.

This method takes care of updating the heap.

This can ONLY be called when you are using Scanners that implement InternalScanner as well as KeyValueScanner (a StoreScanner).

指定者:

next 在接口中 InternalScanner

参数:

result -

返回:

true if more rows exist after this one, false if scanner is done

抛出:

IOException - e

next

public boolean next(List<Cell> result,
           ScannerContext scannerContext)
             throws IOException

从接口复制的说明: InternalScanner

Grab the next row's worth of values.

指定者:

next 在接口中 InternalScanner

参数:

result - return output array

返回:

true if more rows exist after this one, false if scanner is done

抛出:

IOException - e

close

public void close()

从接口复制的说明: KeyValueScanner

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 InternalScanner

指定者:

close 在接口中 KeyValueScanner

seek

public boolean seek(Cell seekKey)
             throws IOException

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

指定者:

seek 在接口中 KeyValueScanner

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

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

指定者:

reseek 在接口中 KeyValueScanner

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

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 NonLazyKeyValueScanner

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

useBloom - whether to enable multi-column Bloom filter optimization

抛出:

IOException

pollRealKV

protected KeyValueScanner pollRealKV()
                              throws IOException

Fetches the top sub-scanner from the priority queue, ensuring that a real seek has been done on it. Works by fetching the top sub-scanner, and if it has not done a real seek, making it do so (which will modify its top KV), putting it back, and repeating this until success. Relies on the fact that on a lazy seek we set the current key of a StoreFileScanner to a KV that is not greater than the real next KV to be read from that file, so the scanner that bubbles up to the top of the heap will have global next KV in this scanner heap if (1) it has done a real seek and (2) its KV is the top among all top KVs (some of which are fake) in the scanner heap.

抛出:

IOException

getHeap

public PriorityQueue<KeyValueScanner> getHeap()

返回:

the current Heap

getScannerOrder

public long getScannerOrder()

从接口复制的说明: KeyValueScanner

Get the order of this KeyValueScanner. This is only relevant for StoreFileScanners and MemStoreScanners (other scanners simply return 0). This is required for comparing multiple files to find out which one has the latest data. StoreFileScanners are ordered from 0 (oldest) to newest in increasing order. MemStoreScanner gets LONG.max since it always contains freshest data.

指定者:

getScannerOrder 在接口中 KeyValueScanner

另请参阅:

KeyValueScanner.getScannerOrder()

getNextIndexedKey

public Cell getNextIndexedKey()

指定者:

getNextIndexedKey 在接口中 KeyValueScanner

覆盖:

getNextIndexedKey 在类中 NonLazyKeyValueScanner

返回:

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.