org.apache.hadoop.hbase.filter
Class PageFilter

java.lang.Object
  extended by org.apache.hadoop.hbase.filter.PageFilter
All Implemented Interfaces:
Filter, org.apache.hadoop.io.Writable

public class PageFilter
extends Object
implements Filter

Implementation of Filter interface that limits results to a specific page size. It terminates scanning once the number of filter-passed rows is > the given page size.

Note that this filter cannot guarantee that the number of results returned to a client are <= page size. This is because the filter is applied separately on different region servers. It does however optimize the scan of individual HRegions by making sure that the page size is never exceeded locally.


Nested Class Summary
 
Nested classes/interfaces inherited from interface org.apache.hadoop.hbase.filter.Filter
Filter.ReturnCode
 
Constructor Summary
PageFilter()
          Default constructor, filters nothing.
PageFilter(long pageSize)
          Constructor that takes a maximum page size.
 
Method Summary
 boolean filterAllRemaining()
          If this returns true, the scan will terminate.
 Filter.ReturnCode filterKeyValue(KeyValue v)
          A way to filter based on the column family, column qualifier and/or the column value.
 boolean filterRow()
          Last chance to veto row based on previous Filter.filterKeyValue(KeyValue) calls.
 boolean filterRowKey(byte[] rowKey, int offset, int length)
          Filters a row based on the row key.
 long getPageSize()
           
 void readFields(DataInput in)
           
 void reset()
          Reset the state of the filter between rows.
 void write(DataOutput out)
           
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

PageFilter

public PageFilter()
Default constructor, filters nothing. Required though for RPC deserialization.


PageFilter

public PageFilter(long pageSize)
Constructor that takes a maximum page size.

Parameters:
pageSize - Maximum result size.
Method Detail

getPageSize

public long getPageSize()

reset

public void reset()
Description copied from interface: Filter
Reset the state of the filter between rows.

Specified by:
reset in interface Filter

filterAllRemaining

public boolean filterAllRemaining()
Description copied from interface: Filter
If this returns true, the scan will terminate.

Specified by:
filterAllRemaining in interface Filter
Returns:
true to end scan, false to continue.

filterRowKey

public boolean filterRowKey(byte[] rowKey,
                            int offset,
                            int length)
Description copied from interface: 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.filterKeyValue(KeyValue) below.

Specified by:
filterRowKey in interface Filter
Parameters:
rowKey - 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).

readFields

public void readFields(DataInput in)
                throws IOException
Specified by:
readFields in interface org.apache.hadoop.io.Writable
Throws:
IOException

write

public void write(DataOutput out)
           throws IOException
Specified by:
write in interface org.apache.hadoop.io.Writable
Throws:
IOException

filterKeyValue

public Filter.ReturnCode filterKeyValue(KeyValue v)
Description copied from interface: 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 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.

Specified by:
filterKeyValue in interface Filter
Parameters:
v - the KeyValue in question
Returns:
code as described below
See Also:
Filter.ReturnCode

filterRow

public boolean filterRow()
Description copied from interface: Filter
Last chance to veto row based on previous Filter.filterKeyValue(KeyValue) 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).

Specified by:
filterRow in interface Filter
Returns:
true to exclude row, false to include row.


Copyright © 2010 The Apache Software Foundation