Filter (Apache HBase 1.2.12 API)

java.lang.Object
- org.apache.hadoop.hbase.filter.Filter

Direct Known Subclasses:

org.apache.hadoop.hbase.filter.FilterBase, FilterList
```
@InterfaceAudience.Public
@InterfaceStability.Stable
public abstract class Filter
extends Object
```
Interface for row and column filters directly applied within the regionserver. A filter can expect the following call sequence:
- reset() : reset the filter state before filtering a new row.
- filterAllRemaining(): true means row scan is over; false means keep going.
- filterRowKey(byte[],int,int): true means drop this row; false means include.
- filterKeyValue(Cell): decides whether to include or exclude this KeyValue. See Filter.ReturnCode.
- transform(KeyValue): if the KeyValue is included, let the filter transform the KeyValue.
- filterRowCells(List): allows direct modification of the final list to be submitted
- filterRow(): last chance to drop entire row based on the sequence of filter calls. Eg: filter a row if it doesn't contain a specified column.
Filter instances are created one per region/scan. This abstract class replaces the old RowFilterInterface. When implementing your own filters, consider inheriting FilterBase to help you reduce boilerplate.
See Also:
FilterBase

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class Filter.ReturnCode
Return codes for filterValue().

Nested Classes
Modifier and Type	Class and Description
`static class`	`Filter.ReturnCode` Return codes for filterValue().

Field Summary

Fields
Modifier and Type Field and Description

protected boolean reversed

Fields
Modifier and Type	Field and Description
`protected boolean`	`reversed`

Constructor Summary

Constructors
Constructor and Description

Filter()

Constructors
Constructor and Description
`Filter()`

Method Summary

Methods
Modifier and Type	Method and Description
`abstract boolean`	`filterAllRemaining()` If this returns true, the scan will terminate.
`abstract Filter.ReturnCode`	`filterKeyValue(Cell v)` A way to filter based on the column family, column qualifier and/or the column value.
`abstract boolean`	`filterRow()` Last chance to veto row based on previous `filterKeyValue(Cell)` calls.
`abstract void`	`filterRowCells(List<Cell> kvs)` Chance to alter the list of Cells to be submitted.
`abstract boolean`	`filterRowKey(byte[] buffer, int offset, int length)` Filters a row based on the row key.
`abstract Cell`	`getNextCellHint(Cell currentKV)` If the filter returns the match code SEEK_NEXT_USING_HINT, then it should also tell which is the next key it must seek to.
`abstract org.apache.hadoop.hbase.KeyValue`	`getNextKeyHint(org.apache.hadoop.hbase.KeyValue currentKV)` Deprecated.
`abstract boolean`	`hasFilterRow()` Primarily used to check for conflicts with scans(such as scans that do not read a full row at a time).
`abstract boolean`	`isFamilyEssential(byte[] name)` Check that given column family is essential for filter to check row.
`boolean`	`isReversed()`
`static Filter`	`parseFrom(byte[] pbBytes)` Concrete implementers can signal a failure condition in their code by throwing an `IOException`.
`abstract void`	`reset()` Reset the state of the filter between rows.
`void`	`setReversed(boolean reversed)` alter the reversed scan flag
`abstract byte[]`	`toByteArray()` TODO: JAVADOC Concrete implementers can signal a failure condition in their code by throwing an `IOException`.
`abstract org.apache.hadoop.hbase.KeyValue`	`transform(org.apache.hadoop.hbase.KeyValue currentKV)` Deprecated.
`abstract Cell`	`transformCell(Cell v)` Give the filter a chance to transform the passed KeyValue.

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

- Field Detail
  - reversed
```
protected transient boolean reversed
```
- Constructor Detail
  - Filter
```
public Filter()
```
- Method Detail
  - reset
```
public abstract void reset()
                    throws IOException
```
    Reset the state of the filter between rows. Concrete implementers can signal a failure condition in their code by throwing an IOException.
    
    Throws:
    
    IOException - in case an I/O or an filter specific failure needs to be signaled.
  - filterRowKey
```
public abstract boolean filterRowKey(byte[] buffer,
                   int offset,
                   int length)
                              throws IOException
```
    Filters a row based on the row key. If this returns true, the entire row will be excluded. If false, each KeyValue in the row will be passed to filterKeyValue(Cell) below. Concrete implementers can signal a failure condition in their code by throwing an IOException.
    
    Parameters:
    buffer - buffer containing row key
    offset - offset into buffer where row key starts
    length - length of the row key
    
    Returns:
    true, remove entire row, false, include the row (maybe).
    
    Throws:
    
    IOException - in case an I/O or an filter specific failure needs to be signaled.
  - filterAllRemaining
```
public abstract boolean filterAllRemaining()
                                    throws IOException
```
    If this returns true, the scan will terminate. Concrete implementers can signal a failure condition in their code by throwing an IOException.
    
    Returns:
    true to end scan, false to continue.
    
    Throws:
    
    IOException - in case an I/O or an filter specific failure needs to be signaled.
  - filterKeyValue
```
public abstract Filter.ReturnCode filterKeyValue(Cell v)
                                          throws IOException
```
    A way to filter based on the column family, column qualifier and/or the column value. Return code is described below. This allows filters to filter only certain number of columns, then terminate without matching ever column. If filterRowKey returns true, filterKeyValue needs to be consistent with it. filterKeyValue can assume that filterRowKey has already been called for the row. If your filter returns ReturnCode.NEXT_ROW, it should return ReturnCode.NEXT_ROW until reset() is called just in case the caller calls for the next row. Concrete implementers can signal a failure condition in their code by throwing an IOException.
    
    Parameters:
    v - the Cell in question
    
    Returns:
    code as described below
    
    Throws:
    
    IOException - in case an I/O or an filter specific failure needs to be signaled.
    See Also:
    Filter.ReturnCode
  - transformCell
```
public abstract Cell transformCell(Cell v)
                            throws IOException
```
    Give the filter a chance to transform the passed KeyValue. If the Cell is changed a new Cell object must be returned.
    
    Parameters:
    v - the KeyValue in question
    
    Returns:
    the changed KeyValue
    
    Throws:
    
    IOException - in case an I/O or an filter specific failure needs to be signaled.
    See Also:
    The transformed KeyValue is what is eventually returned to the client. Most filters will return the passed KeyValue unchanged., for an example of a transformation. Concrete implementers can signal a failure condition in their code by throwing an {@link IOException}.
  - transform
```
@Deprecated
public abstract org.apache.hadoop.hbase.KeyValue transform(org.apache.hadoop.hbase.KeyValue currentKV)
                                                    throws IOException
```
    Deprecated.
    
    WARNING: please to not override this method. Instead override transformCell(Cell). This is for transition from 0.94 -> 0.96
    
    Throws:
    
    IOException
  - filterRowCells
```
public abstract void filterRowCells(List<Cell> kvs)
                             throws IOException
```
    Chance to alter the list of Cells to be submitted. Modifications to the list will carry on Concrete implementers can signal a failure condition in their code by throwing an IOException.
    
    Parameters:
    kvs - the list of Cells to be filtered
    
    Throws:
    
    IOException - in case an I/O or an filter specific failure needs to be signaled.
  - hasFilterRow
```
public abstract boolean hasFilterRow()
```
    Primarily used to check for conflicts with scans(such as scans that do not read a full row at a time).
    
    Returns:
    True if this filter actively uses filterRowCells(List) or filterRow().
  - filterRow
```
public abstract boolean filterRow()
                           throws IOException
```
    Last chance to veto row based on previous filterKeyValue(Cell) calls. The filter needs to retain state then return a particular value for this call if they wish to exclude a row if a certain column is missing (for example). Concrete implementers can signal a failure condition in their code by throwing an IOException.
    
    Returns:
    true to exclude row, false to include row.
    
    Throws:
    
    IOException - in case an I/O or an filter specific failure needs to be signaled.
  - getNextKeyHint
```
@Deprecated
public abstract org.apache.hadoop.hbase.KeyValue getNextKeyHint(org.apache.hadoop.hbase.KeyValue currentKV)
                                                         throws IOException
```
    Deprecated.
    
    Parameters:
    currentKV -
    
    Returns:
    KeyValue which must be next seeked. return null if the filter is not sure which key to seek to next.
    
    Throws:
    
    IOException - Function is Deprecated. Use getNextCellHint(Cell) instead.
  - getNextCellHint
```
public abstract Cell getNextCellHint(Cell currentKV)
                              throws IOException
```
    If the filter returns the match code SEEK_NEXT_USING_HINT, then it should also tell which is the next key it must seek to. After receiving the match code SEEK_NEXT_USING_HINT, the QueryMatcher would call this function to find out which key it must next seek to. Concrete implementers can signal a failure condition in their code by throwing an IOException.
    
    Returns:
    KeyValue which must be next seeked. return null if the filter is not sure which key to seek to next.
    
    Throws:
    
    IOException - in case an I/O or an filter specific failure needs to be signaled.
  - isFamilyEssential
```
public abstract boolean isFamilyEssential(byte[] name)
                                   throws IOException
```
    Check that given column family is essential for filter to check row. Most filters always return true here. But some could have more sophisticated logic which could significantly reduce scanning process by not even touching columns until we are 100% sure that it's data is needed in result. Concrete implementers can signal a failure condition in their code by throwing an IOException.
    
    Throws:
    
    IOException - in case an I/O or an filter specific failure needs to be signaled.
  - toByteArray
```
public abstract byte[] toByteArray()
                            throws IOException
```
    TODO: JAVADOC Concrete implementers can signal a failure condition in their code by throwing an IOException.
    
    Returns:
    The filter serialized using pb
    
    Throws:
    
    IOException - in case an I/O or an filter specific failure needs to be signaled.
  - parseFrom
```
public static Filter parseFrom(byte[] pbBytes)
                        throws org.apache.hadoop.hbase.exceptions.DeserializationException
```
    Concrete implementers can signal a failure condition in their code by throwing an IOException.
    
    Parameters:
    pbBytes - A pb serialized Filter instance
    
    Returns:
    An instance of Filter made from bytes
    
    Throws:
    
    org.apache.hadoop.hbase.exceptions.DeserializationException
    See Also:
    toByteArray()
  - setReversed
```
public void setReversed(boolean reversed)
```
    alter the reversed scan flag
    
    Parameters:
    reversed - flag
  - isReversed
```
public boolean isReversed()
```

Class Filter

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

reversed

Constructor Detail

Filter

Method Detail

reset

filterRowKey

filterAllRemaining

filterKeyValue

transformCell

transform

filterRowCells

hasFilterRow

filterRow

getNextKeyHint

getNextCellHint

isFamilyEssential

toByteArray

parseFrom

setReversed

isReversed