org.apache.hadoop.hbase.filter

Class ColumnPaginationFilter

java.lang.Object

org.apache.hadoop.hbase.filter.Filter

org.apache.hadoop.hbase.filter.FilterBase

org.apache.hadoop.hbase.filter.ColumnPaginationFilter

@InterfaceAudience.Public
public class ColumnPaginationFilter
extends FilterBase

A filter, based on the ColumnCountGetFilter, takes two arguments: limit and offset. This filter can be used for row-based indexing, where references to other tables are stored across many columns, in order to efficient lookups and paginated results for end users. Only most recent versions are considered for pagination.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.hadoop.hbase.filter.Filter

Filter.ReturnCode

Field Summary

Fields

Modifier and Type	Field and Description
private byte[]	columnOffset
private int	count
private int	limit
private int	offset

Fields inherited from class org.apache.hadoop.hbase.filter.Filter

reversed

Constructor Summary

Constructors

Constructor and Description
ColumnPaginationFilter(int limit, byte[] columnOffset) Initializes filter with a string/bookmark based offset and limit.
ColumnPaginationFilter(int limit, int offset) Initializes filter with an integer offset and limit.

Method Summary

Modifier and Type	Method and Description
(package private) boolean	areSerializedFieldsEqual(Filter o) Default implementation so that writers of custom filters aren't forced to implement.
static Filter	createFilterFromArguments(ArrayList<byte[]> filterArguments)
boolean	equals(Object obj)
Filter.ReturnCode	filterCell(Cell c) A way to filter based on the column family, column qualifier and/or the column value.
Filter.ReturnCode	filterKeyValue(Cell c) Deprecated.
boolean	filterRowKey(Cell cell) Filters a row based on the row key.
byte[]	getColumnOffset()
int	getLimit()
Cell	getNextCellHint(Cell cell) Filters that are not sure which key must be next seeked to, can inherit this implementation that, by default, returns a null Cell.
int	getOffset()
int	hashCode()
static ColumnPaginationFilter	parseFrom(byte[] pbBytes)
void	reset() Filters that are purely stateless and do nothing in their reset() methods can inherit this null/empty implementation.
byte[]	toByteArray() Return length 0 byte array for Filters that don't require special serialization
String	toString() Return filter's info for debugging and logging purpose.

Methods inherited from class org.apache.hadoop.hbase.filter.FilterBase

filterAllRemaining, filterRow, filterRowCells, filterRowKey, hasFilterRow, isFamilyEssential, transformCell

Methods inherited from class org.apache.hadoop.hbase.filter.Filter

isReversed, setReversed

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

limit

private int limit

offset

private int offset

columnOffset

private byte[] columnOffset

count

private int count

Constructor Detail

ColumnPaginationFilter

public ColumnPaginationFilter(int limit,
                              int offset)

Initializes filter with an integer offset and limit. The offset is arrived at scanning sequentially and skipping entries. @limit number of columns are then retrieved. If multiple column families are involved, the columns may be spread across them.

Parameters:

limit - Max number of columns to return.

offset - The integer offset where to start pagination.

ColumnPaginationFilter

public ColumnPaginationFilter(int limit,
                              byte[] columnOffset)

Initializes filter with a string/bookmark based offset and limit. The offset is arrived at, by seeking to it using scanner hints. If multiple column families are involved, pagination starts at the first column family which contains @columnOffset. Columns are then retrieved sequentially upto @limit number of columns which maybe spread across multiple column families, depending on how the scan is setup.

Parameters:

limit - Max number of columns to return.

columnOffset - The string/bookmark offset on where to start pagination.

Method Detail

getLimit

public int getLimit()

Returns:

limit

getOffset

public int getOffset()

Returns:

offset

getColumnOffset

public byte[] getColumnOffset()

Returns:

columnOffset

filterRowKey

public boolean filterRowKey(Cell cell)
                     throws IOException

Description copied from class: Filter

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

Overrides:

filterRowKey in class FilterBase

Parameters:

cell - 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.

filterKeyValue

@Deprecated
public Filter.ReturnCode filterKeyValue(Cell c)

Deprecated.

Description copied from class: Filter

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 Filter.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.

Overrides:

filterKeyValue in class Filter

Parameters:

c - the Cell in question

Returns:

code as described below, Filter.ReturnCode.INCLUDE by default

See Also:

Filter.ReturnCode

filterCell

public Filter.ReturnCode filterCell(Cell c)

Description copied from class: Filter

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 Filter.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.

Overrides:

filterCell in class Filter

Parameters:

c - the Cell in question

Returns:

code as described below

See Also:

Filter.ReturnCode

getNextCellHint

public Cell getNextCellHint(Cell cell)

Description copied from class: FilterBase

Filters that are not sure which key must be next seeked to, can inherit this implementation that, by default, returns a null Cell. 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.

Overrides:

getNextCellHint in class FilterBase

Returns:

KeyValue which must be next seeked. return null if the filter is not sure which key to seek to next.

reset

public void reset()

Description copied from class: FilterBase

Filters that are purely stateless and do nothing in their reset() methods can inherit this null/empty implementation. Reset the state of the filter between rows. Concrete implementers can signal a failure condition in their code by throwing an IOException.

Overrides:

reset in class FilterBase

createFilterFromArguments

public static Filter createFilterFromArguments(ArrayList<byte[]> filterArguments)

toByteArray

public byte[] toByteArray()

Description copied from class: FilterBase

Return length 0 byte array for Filters that don't require special serialization

Overrides:

toByteArray in class FilterBase

Returns:

The filter serialized using pb

parseFrom

public static ColumnPaginationFilter parseFrom(byte[] pbBytes)
                                        throws DeserializationException

Parameters:

pbBytes - A pb serialized ColumnPaginationFilter instance

Returns:

An instance of ColumnPaginationFilter made from bytes

Throws:

DeserializationException

See Also:

toByteArray()

areSerializedFieldsEqual

boolean areSerializedFieldsEqual(Filter o)

Description copied from class: FilterBase

Default implementation so that writers of custom filters aren't forced to implement.

Overrides:

areSerializedFieldsEqual in class FilterBase

Parameters:

o - the other filter to compare with

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.

toString

public String toString()

Description copied from class: FilterBase

Return filter's info for debugging and logging purpose.

Overrides:

toString in class FilterBase

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object