org.apache.hadoop.hbase.filter

Class Filter

java.lang.Object

org.apache.hadoop.hbase.filter.Filter

Direct Known Subclasses:

FilterBase, FilterList, FilterWrapper

@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().

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	reversed

Constructor Summary

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 KeyValue	getNextKeyHint(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 KeyValue	transform(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 KeyValue transform(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 KeyValue getNextKeyHint(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 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:

DeserializationException

IOException - in case an I/O or an filter specific failure needs to be signaled.

See Also:

toByteArray()

setReversed

public void setReversed(boolean reversed)

alter the reversed scan flag

Parameters:

reversed - flag

isReversed

public boolean isReversed()