Package org.apache.hadoop.hbase.filter

Class Filter

java.lang.Object

org.apache.hadoop.hbase.filter.Filter

Direct Known Subclasses:

FilterBase, FilterWrapper

@Public
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(Cell): true means drop this row; false means include.
• filterCell(Cell): decides whether to include or exclude this Cell. See Filter.ReturnCode.
• transformCell(Cell): if the Cell is included, let the filter transform the Cell.
• 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	Description
static enum	Filter.ReturnCode	Return codes for filterValue().

Field Summary

Fields

Modifier and Type	Field	Description
protected boolean	reversed

Constructor Summary

Constructors

Constructor	Description
Filter()

Method Summary

Modifier and Type	Method	Description
(package private) abstract boolean	areSerializedFieldsEqual(Filter other)	Concrete implementers can signal a failure condition in their code by throwing an IOException.
abstract boolean	filterAllRemaining()	If this returns true, the scan will terminate.
Filter.ReturnCode	filterCell(Cell c)	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 filterCell(Cell) calls.
abstract void	filterRowCells(List<Cell> kvs)	Chance to alter the list of Cells to be submitted.
abstract boolean	filterRowKey(Cell firstRowCell)	Filters a row based on the row key.
abstract Cell	getNextCellHint(Cell currentCell)	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 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 Cell	transformCell(Cell v)	Give the filter a chance to transform the passed Cell.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

reversed

protected transient boolean reversed

Constructor Details

Filter

public Filter()

Method Details

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(Cell firstRowCell)
                              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 filterCell(Cell) below. If filterAllRemaining() returns true, then filterRowKey(Cell) should also return true. Concrete implementers can signal a failure condition in their code by throwing an IOException.

Parameters:

firstRowCell - The first cell coming in the new row

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.

filterCell

public Filter.ReturnCode filterCell(Cell c)
                             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, filterCell needs to be consistent with it. filterCell 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:

c - 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 Cell. If the Cell is changed a new Cell object must be returned.

NOTICE: Filter will be evaluate at server side so the returned Cell must be an ExtendedCell, although it is marked as IA.Private.

Parameters:

v - the Cell in question

Returns:

the changed Cell

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 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 filterCell(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.

getNextCellHint

public abstract Cell getNextCellHint(Cell currentCell)
                              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. NOTICE: Filter will be evaluate at server side so the returned Cell must be an ExtendedCell, although it is marked as IA.Private.

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 - if an error occurred

See Also:

• toByteArray()

areSerializedFieldsEqual

abstract boolean areSerializedFieldsEqual(Filter other)

Concrete implementers can signal a failure condition in their code by throwing an IOException.

Returns:

true if and only if the fields of the filter that are serialized are equal to the corresponding fields in other. Used for testing.

setReversed

public void setReversed(boolean reversed)

alter the reversed scan flag

Parameters:

reversed - flag

isReversed

public boolean isReversed()