PrefixTreeSeeker (Apache HBase 1.2.12 API)

java.lang.Object
- org.apache.hadoop.hbase.codec.prefixtree.PrefixTreeSeeker

All Implemented Interfaces:

DataBlockEncoder.EncodedSeeker
```
@InterfaceAudience.Private
public class PrefixTreeSeeker
extends Object
implements DataBlockEncoder.EncodedSeeker
```
These methods have the same definition as any implementation of the EncodedSeeker. In the future, the EncodedSeeker could be modified to work with the Cell interface directly. It currently returns a new KeyValue object each time getKeyValue is called. This is not horrible, but in order to create a new KeyValue object, we must first allocate a new byte[] and copy in the data from the PrefixTreeCell. It is somewhat heavyweight right now.

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`private static class`	`PrefixTreeSeeker.ClonedPrefixTreeCell` Cloned version of the PrefixTreeCell where except the value part, the rest of the key part is deep copied

Field Summary

Fields
Modifier and Type	Field and Description
`protected ByteBuffer`	`block`
`protected boolean`	`includeMvccVersion`
`protected PrefixTreeArraySearcher`	`ptSearcher`
`private static boolean`	`USE_POSITION_BEFORE`

Constructor Summary

Constructors
Constructor and Description

PrefixTreeSeeker(boolean includeMvccVersion)

Constructors
Constructor and Description
`PrefixTreeSeeker(boolean includeMvccVersion)`

Method Summary

Methods
Modifier and Type	Method and Description
`boolean`	`advance()`
`int`	`compareKey(KeyValue.KVComparator comparator, byte[] key, int offset, int length)` Compare the given key against the current key
`int`	`compareKey(KeyValue.KVComparator comparator, Cell key)`
`Cell`	`get()` Currently unused.
`ByteBuffer`	`getKeyDeepCopy()` Does a deep copy of the key at the current position.
`Cell`	`getKeyValue()` currently must do deep copy into new array
`ByteBuffer`	`getValueShallowCopy()` Does a shallow copy of the value at the current position.
`boolean`	`next()` Move to next position
`void`	`releaseCurrentSearcher()` Currently unused.
`void`	`rewind()` Set position to beginning of given block
`int`	`seekToKeyInBlock(byte[] keyOnlyBytes, int offset, int length, boolean forceBeforeOnExactMatch)` Seek forward only (should be called reseekToKeyInBlock?).
`int`	`seekToKeyInBlock(Cell key, boolean forceBeforeOnExactMatch)` Moves the seeker position within the current block to: the last key that that is less than or equal to the given key if `seekBefore` is false the last key that is strictly less than the given key if `seekBefore` is true.
`protected int`	`seekToOrBeforeUsingPositionAtOrAfter(byte[] keyOnlyBytes, int offset, int length, boolean seekBefore)`
`protected int`	`seekToOrBeforeUsingPositionAtOrAfter(Cell kv, boolean seekBefore)`
`protected int`	`seekToOrBeforeUsingPositionAtOrBefore(byte[] keyOnlyBytes, int offset, int length, boolean seekBefore)`
`protected int`	`seekToOrBeforeUsingPositionAtOrBefore(Cell kv, boolean seekBefore)`
`void`	`setCurrentBuffer(ByteBuffer fullBlockBuffer)` Set on which buffer there will be done seeking.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - block
```
protected ByteBuffer block
```
  - includeMvccVersion
```
protected boolean includeMvccVersion
```
  - ptSearcher
```
protected PrefixTreeArraySearcher ptSearcher
```
  - USE_POSITION_BEFORE
```
private static final boolean USE_POSITION_BEFORE
```
    See Also:
    Constant Field Values
- Constructor Detail
  - PrefixTreeSeeker
```
public PrefixTreeSeeker(boolean includeMvccVersion)
```
- Method Detail
  - setCurrentBuffer
```
public void setCurrentBuffer(ByteBuffer fullBlockBuffer)
```
    Description copied from interface: DataBlockEncoder.EncodedSeeker
    
    Set on which buffer there will be done seeking.
    
    Specified by:
    
    setCurrentBuffer in interface DataBlockEncoder.EncodedSeeker
    
    Parameters:
    fullBlockBuffer - Used for seeking.
  - releaseCurrentSearcher
```
public void releaseCurrentSearcher()
```
    Currently unused.
    TODO performance leak. should reuse the searchers. hbase does not currently have a hook where this can be called
  - getKeyDeepCopy
```
public ByteBuffer getKeyDeepCopy()
```
    Description copied from interface: DataBlockEncoder.EncodedSeeker
    
    Does a deep copy of the key at the current position. A deep copy is necessary because buffers are reused in the decoder.
    
    Specified by:
    
    getKeyDeepCopy in interface DataBlockEncoder.EncodedSeeker
    
    Returns:
    key at current position
  - getValueShallowCopy
```
public ByteBuffer getValueShallowCopy()
```
    Description copied from interface: DataBlockEncoder.EncodedSeeker
    
    Does a shallow copy of the value at the current position. A shallow copy is possible because the returned buffer refers to the backing array of the original encoded buffer.
    
    Specified by:
    
    getValueShallowCopy in interface DataBlockEncoder.EncodedSeeker
    
    Returns:
    value at current position
  - getKeyValue
```
public Cell getKeyValue()
```
    currently must do deep copy into new array
    
    Specified by:
    
    getKeyValue in interface DataBlockEncoder.EncodedSeeker
    
    Returns:
    the KeyValue object at the current position. Includes memstore timestamp.
  - get
```
public Cell get()
```
    Currently unused.
    A nice, lightweight reference, though the underlying cell is transient. This method may return the same reference to the backing PrefixTreeCell repeatedly, while other implementations may return a different reference for each Cell.
    The goal will be to transition the upper layers of HBase, like Filters and KeyValueHeap, to use this method instead of the getKeyValue() methods above.
  - rewind
```
public void rewind()
```
    Description copied from interface: DataBlockEncoder.EncodedSeeker
    
    Set position to beginning of given block
    
    Specified by:
    
    rewind in interface DataBlockEncoder.EncodedSeeker
  - next
```
public boolean next()
```
    Description copied from interface: DataBlockEncoder.EncodedSeeker
    
    Move to next position
    
    Specified by:
    
    next in interface DataBlockEncoder.EncodedSeeker
    
    Returns:
    true on success, false if there is no more positions.
  - advance
```
public boolean advance()
```
  - seekToKeyInBlock
```
public int seekToKeyInBlock(byte[] keyOnlyBytes,
                   int offset,
                   int length,
                   boolean forceBeforeOnExactMatch)
```
    Seek forward only (should be called reseekToKeyInBlock?).
    If the exact key is found look at the seekBefore variable and:
    - if true: go to the previous key if it's true
    - if false: stay on the exact key
    If the exact key is not found, then go to the previous key *if possible*, but remember to leave the scanner in a valid state if possible.
    
    Specified by:
    
    seekToKeyInBlock in interface DataBlockEncoder.EncodedSeeker
    
    Parameters:
    keyOnlyBytes - KeyValue format of a Cell's key at which to position the seeker
    offset - offset into the keyOnlyBytes array
    length - number of bytes of the keyOnlyBytes array to use
    forceBeforeOnExactMatch - if an exact match is found and seekBefore=true, back up 1 Cell
    
    Returns:
    0 if the seeker is on the exact key
    1 if the seeker is not on the key for any reason, including seekBefore being true
  - seekToOrBeforeUsingPositionAtOrBefore
```
protected int seekToOrBeforeUsingPositionAtOrBefore(byte[] keyOnlyBytes,
                                        int offset,
                                        int length,
                                        boolean seekBefore)
```
  - seekToOrBeforeUsingPositionAtOrBefore
```
protected int seekToOrBeforeUsingPositionAtOrBefore(Cell kv,
                                        boolean seekBefore)
```
  - seekToOrBeforeUsingPositionAtOrAfter
```
protected int seekToOrBeforeUsingPositionAtOrAfter(byte[] keyOnlyBytes,
                                       int offset,
                                       int length,
                                       boolean seekBefore)
```
  - seekToOrBeforeUsingPositionAtOrAfter
```
protected int seekToOrBeforeUsingPositionAtOrAfter(Cell kv,
                                       boolean seekBefore)
```
  - compareKey
```
public int compareKey(KeyValue.KVComparator comparator,
             byte[] key,
             int offset,
             int length)
```
    Description copied from interface: DataBlockEncoder.EncodedSeeker
    
    Compare the given key against the current key
    
    Specified by:
    
    compareKey in interface DataBlockEncoder.EncodedSeeker
    
    Returns:
    -1 is the passed key is smaller than the current key, 0 if equal and 1 if greater
  - seekToKeyInBlock
```
public int seekToKeyInBlock(Cell key,
                   boolean forceBeforeOnExactMatch)
```
    Description copied from interface: DataBlockEncoder.EncodedSeeker
    Moves the seeker position within the current block to:
    - the last key that that is less than or equal to the given key if seekBefore is false
    - the last key that is strictly less than the given key if seekBefore is true. The caller is responsible for loading the previous block if the requested key turns out to be the first key of the current block.
    Specified by:
    
    seekToKeyInBlock in interface DataBlockEncoder.EncodedSeeker
    
    Parameters:
    key - - Cell to which the seek should happen
    forceBeforeOnExactMatch - find the key strictly less than the given key in case of an exact match. Does not matter in case of an inexact match.
    
    Returns:
    0 on exact match, 1 on inexact match.
  - compareKey
```
public int compareKey(KeyValue.KVComparator comparator,
             Cell key)
```
    Specified by:
    
    compareKey in interface DataBlockEncoder.EncodedSeeker

Class PrefixTreeSeeker

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

block

includeMvccVersion

ptSearcher

USE_POSITION_BEFORE

Constructor Detail

PrefixTreeSeeker

Method Detail

setCurrentBuffer

releaseCurrentSearcher

getKeyDeepCopy

getValueShallowCopy

getKeyValue

get

rewind

next

advance

seekToKeyInBlock

seekToOrBeforeUsingPositionAtOrBefore

seekToOrBeforeUsingPositionAtOrBefore

seekToOrBeforeUsingPositionAtOrAfter

seekToOrBeforeUsingPositionAtOrAfter

compareKey

seekToKeyInBlock

compareKey