@InterfaceAudience.Private public class KeyValueHeap extends NonReversedNonLazyKeyValueScanner implements KeyValueScanner, InternalScanner
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.
Modifier and Type | Class and Description |
---|---|
protected static class |
KeyValueHeap.KVScannerComparator |
Modifier and Type | Field and Description |
---|---|
protected KeyValueHeap.KVScannerComparator |
comparator |
protected KeyValueScanner |
current
The current sub-scanner, i.e.
|
protected java.util.PriorityQueue<KeyValueScanner> |
heap |
Constructor and Description |
---|
KeyValueHeap(java.util.List<? extends KeyValueScanner> scanners,
KeyValue.KVComparator comparator)
Constructor.
|
Modifier and Type | Method and Description |
---|---|
void |
close()
Close the KeyValue scanner.
|
java.util.PriorityQueue<KeyValueScanner> |
getHeap() |
Cell |
getNextIndexedKey() |
long |
getSequenceID()
Get the sequence id associated with this KeyValueScanner.
|
Cell |
next()
Return the next Cell in this scanner, iterating the scanner
|
boolean |
next(java.util.List<Cell> result)
Gets the next row of keys from the top-most scanner.
|
boolean |
next(java.util.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.
|
backwardSeek, seekToLastRow, seekToPreviousRow
doRealSeek, enforceSeek, isFileScanner, realSeekDone, shouldUseScanner
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
backwardSeek, enforceSeek, isFileScanner, realSeekDone, seekToLastRow, seekToPreviousRow, shouldUseScanner
protected java.util.PriorityQueue<KeyValueScanner> heap
protected KeyValueScanner current
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.protected KeyValueHeap.KVScannerComparator comparator
public KeyValueHeap(java.util.List<? extends KeyValueScanner> scanners, KeyValue.KVComparator comparator) throws java.io.IOException
scanners
- comparator
- java.io.IOException
public Cell peek()
KeyValueScanner
peek
in interface KeyValueScanner
public Cell next() throws java.io.IOException
KeyValueScanner
next
in interface KeyValueScanner
java.io.IOException
public boolean next(java.util.List<Cell> result) throws java.io.IOException
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
).
next
in interface InternalScanner
result
- java.io.IOException
- epublic boolean next(java.util.List<Cell> result, ScannerContext scannerContext) throws java.io.IOException
InternalScanner
next
in interface InternalScanner
result
- return output arrayjava.io.IOException
- epublic void close()
KeyValueScanner
close
in interface java.io.Closeable
close
in interface java.lang.AutoCloseable
close
in interface InternalScanner
close
in interface KeyValueScanner
public boolean seek(Cell seekKey) throws java.io.IOException
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)
.
seek
in interface KeyValueScanner
seekKey
- KeyValue to seek at or afterjava.io.IOException
public boolean reseek(Cell seekKey) throws java.io.IOException
seek(Cell)
function except
that scanner.seek(seekKey) is changed to scanner.reseek(seekKey).reseek
in interface KeyValueScanner
seekKey
- seek value (should be non-null)java.io.IOException
public boolean requestSeek(Cell key, boolean forward, boolean useBloom) throws java.io.IOException
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.requestSeek
in interface KeyValueScanner
requestSeek
in class NonLazyKeyValueScanner
forward
- do a forward-only "reseek" instead of a random-access seekuseBloom
- whether to enable multi-column Bloom filter optimizationjava.io.IOException
protected KeyValueScanner pollRealKV() throws java.io.IOException
java.io.IOException
public java.util.PriorityQueue<KeyValueScanner> getHeap()
public long getSequenceID()
KeyValueScanner
getSequenceID
in interface KeyValueScanner
public Cell getNextIndexedKey()
getNextIndexedKey
in interface KeyValueScanner
getNextIndexedKey
in class NonLazyKeyValueScanner