ScanWildcardColumnTracker (Apache HBase 1.2.12 API)

java.lang.Object
- org.apache.hadoop.hbase.regionserver.ScanWildcardColumnTracker

All Implemented Interfaces:

ColumnTracker
```
@InterfaceAudience.Private
public class ScanWildcardColumnTracker
extends Object
implements ColumnTracker
```
Keeps track of the columns for a scan if they are not explicitly specified

Field Summary

Fields
Modifier and Type	Field and Description
`private byte[]`	`columnBuffer`
`private int`	`columnLength`
`private int`	`columnOffset`
`private int`	`currentCount`
`private long`	`latestTSOfCurrentColumn`
`private byte`	`latestTypeOfCurrentColumn`
`private int`	`maxVersions`
`private int`	`minVersions`
`private long`	`oldestStamp`

Constructor Summary

Constructors
Constructor and Description
`ScanWildcardColumnTracker(int minVersion, int maxVersion, long oldestUnexpiredTS)` Return maxVersions of every row.

Method Summary

Methods
Modifier and Type	Method and Description
`ScanQueryMatcher.MatchCode`	`checkColumn(byte[] bytes, int offset, int length, byte type)` Checks if the column is present in the list of requested columns by returning the match code instance.
`private ScanQueryMatcher.MatchCode`	`checkVersion(byte type, long timestamp)` Check whether this version should be retained.
`ScanQueryMatcher.MatchCode`	`checkVersions(byte[] bytes, int offset, int length, long timestamp, byte type, boolean ignoreCount)` Keeps track of the number of versions for the columns asked for.
`boolean`	`done()` We can never know a-priori if we are done, so always return false.
`ColumnCount`	`getColumnHint()` Used by matcher and scan/get to get a hint of the next column to seek to after checkColumn() returns SKIP.
`ScanQueryMatcher.MatchCode`	`getNextRowOrNextColumn(byte[] bytes, int offset, int qualLength)` Retrieve the MatchCode for the next row or column
`boolean`	`isDone(long timestamp)` Give the tracker a chance to declare it's done based on only the timestamp to allow an early out.
`private boolean`	`isExpired(long timestamp)`
`void`	`reset()` Resets the Matcher
`private void`	`resetBuffer(byte[] bytes, int offset, int length)`
`private void`	`resetTSAndType()`
`private boolean`	`sameAsPreviousTSAndType(long timestamp, byte type)`
`private void`	`setTSAndType(long timestamp, byte type)`

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

- Field Detail
  - columnBuffer
```
private byte[] columnBuffer
```
  - columnOffset
```
private int columnOffset
```
  - columnLength
```
private int columnLength
```
  - currentCount
```
private int currentCount
```
  - maxVersions
```
private int maxVersions
```
  - minVersions
```
private int minVersions
```
  - latestTSOfCurrentColumn
```
private long latestTSOfCurrentColumn
```
  - latestTypeOfCurrentColumn
```
private byte latestTypeOfCurrentColumn
```
  - oldestStamp
```
private long oldestStamp
```
- Constructor Detail
  - ScanWildcardColumnTracker
```
public ScanWildcardColumnTracker(int minVersion,
                         int maxVersion,
                         long oldestUnexpiredTS)
```
    Return maxVersions of every row.
    
    Parameters:
    minVersion - Minimum number of versions to keep
    maxVersion - Maximum number of versions to return
    oldestUnexpiredTS - oldest timestamp that has not expired according to the TTL.
- Method Detail
  - checkColumn
```
public ScanQueryMatcher.MatchCode checkColumn(byte[] bytes,
                                     int offset,
                                     int length,
                                     byte type)
                                       throws IOException
```
    Checks if the column is present in the list of requested columns by returning the match code instance. It does not check against the number of versions for the columns asked for. To do the version check, one has to call ColumnTracker.checkVersions(byte[], int, int, long, byte, boolean) method based on the return type (INCLUDE) of this method. The values that can be returned by this method are ScanQueryMatcher.MatchCode.INCLUDE, ScanQueryMatcher.MatchCode.SEEK_NEXT_COL and ScanQueryMatcher.MatchCode.SEEK_NEXT_ROW. This receives puts *and* deletes.
    
    Specified by:
    
    checkColumn in interface ColumnTracker
    
    type - The type of the KeyValue
    
    Returns:
    The match code instance.
    
    Throws:
    
    IOException - in case there is an internal consistency problem caused by a data corruption.
  - checkVersions
```
public ScanQueryMatcher.MatchCode checkVersions(byte[] bytes,
                                       int offset,
                                       int length,
                                       long timestamp,
                                       byte type,
                                       boolean ignoreCount)
                                         throws IOException
```
    Keeps track of the number of versions for the columns asked for. It assumes that the user has already checked if the keyvalue needs to be included by calling the ColumnTracker.checkColumn(byte[], int, int, byte) method. The enum values returned by this method are ScanQueryMatcher.MatchCode.SKIP, ScanQueryMatcher.MatchCode.INCLUDE, ScanQueryMatcher.MatchCode.INCLUDE_AND_SEEK_NEXT_COL and ScanQueryMatcher.MatchCode.INCLUDE_AND_SEEK_NEXT_ROW. Implementations which include all the columns could just return ScanQueryMatcher.MatchCode.INCLUDE in the ColumnTracker.checkColumn(byte[], int, int, byte) method and perform all the operations in this checkVersions method. This receives puts *and* deletes. Deletes do not count as a version, but rather take the version of the previous put (so eventually all but the last can be reclaimed).
    
    Specified by:
    
    checkVersions in interface ColumnTracker
    
    timestamp - The timeToLive to enforce.
    type - the type of the key value (Put/Delete)
    ignoreCount - indicates if the KV needs to be excluded while counting (used during compactions. We only count KV's that are older than all the scanners' read points.)
    
    Returns:
    the scan query matcher match code instance
    
    Throws:
    
    IOException - in case there is an internal consistency problem caused by a data corruption.
  - resetBuffer
```
private void resetBuffer(byte[] bytes,
               int offset,
               int length)
```
  - checkVersion
```
private ScanQueryMatcher.MatchCode checkVersion(byte type,
                                      long timestamp)
```
    Check whether this version should be retained. There are 4 variables considered: If this version is past max versions -> skip it If this kv has expired or was deleted, check min versions to decide whther to skip it or not. Increase the version counter unless this is a delete
  - reset
```
public void reset()
```
    Description copied from interface: ColumnTracker
    
    Resets the Matcher
    
    Specified by:
    
    reset in interface ColumnTracker
  - resetTSAndType
```
private void resetTSAndType()
```
  - setTSAndType
```
private void setTSAndType(long timestamp,
                byte type)
```
  - sameAsPreviousTSAndType
```
private boolean sameAsPreviousTSAndType(long timestamp,
                              byte type)
```
  - isExpired
```
private boolean isExpired(long timestamp)
```
  - getColumnHint
```
public ColumnCount getColumnHint()
```
    Used by matcher and scan/get to get a hint of the next column to seek to after checkColumn() returns SKIP. Returns the next interesting column we want, or NULL there is none (wildcard scanner).
    
    Specified by:
    
    getColumnHint in interface ColumnTracker
    
    Returns:
    The column count.
  - done
```
public boolean done()
```
    We can never know a-priori if we are done, so always return false.
    
    Specified by:
    
    done in interface ColumnTracker
    
    Returns:
    false
  - getNextRowOrNextColumn
```
public ScanQueryMatcher.MatchCode getNextRowOrNextColumn(byte[] bytes,
                                                int offset,
                                                int qualLength)
```
    Description copied from interface: ColumnTracker
    
    Retrieve the MatchCode for the next row or column
    
    Specified by:
    
    getNextRowOrNextColumn in interface ColumnTracker
  - isDone
```
public boolean isDone(long timestamp)
```
    Description copied from interface: ColumnTracker
    
    Give the tracker a chance to declare it's done based on only the timestamp to allow an early out.
    
    Specified by:
    
    isDone in interface ColumnTracker
    
    Returns:
    true to early out based on timestamp.

Class ScanWildcardColumnTracker

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

columnBuffer

columnOffset

columnLength

currentCount

maxVersions

minVersions

latestTSOfCurrentColumn

latestTypeOfCurrentColumn

oldestStamp

Constructor Detail

ScanWildcardColumnTracker

Method Detail

checkColumn

checkVersions

resetBuffer

checkVersion

reset

resetTSAndType

setTSAndType

sameAsPreviousTSAndType

isExpired

getColumnHint

done

getNextRowOrNextColumn

isDone