org.apache.accumulo.core.iterators
Class Filter

java.lang.Object
  extended by org.apache.accumulo.core.iterators.WrappingIterator
      extended by org.apache.accumulo.core.iterators.Filter
All Implemented Interfaces:
OptionDescriber, SortedKeyValueIterator<Key,Value>
Direct Known Subclasses:
AgeOffFilter, ColumnAgeOffFilter, ColumnQualifierFilter, GrepIterator, RegExFilter, ReqVisFilter, TimestampFilter, VisibilityFilter

public abstract class Filter
extends WrappingIterator
implements OptionDescriber

A SortedKeyValueIterator that filters entries from its source iterator. Subclasses must implement an accept method: public boolean accept(Key k, Value v); Key/Value pairs for which the accept method returns true are said to match the filter. By default, this class iterates over entries that match its filter. This iterator takes an optional "negate" boolean parameter that defaults to false. If negate is set to true, this class instead omits entries that match its filter, thus iterating over entries that do not match its filter.


Nested Class Summary
 
Nested classes/interfaces inherited from interface org.apache.accumulo.core.iterators.OptionDescriber
OptionDescriber.IteratorOptions
 
Field Summary
protected static String NEGATE
           
 
Constructor Summary
Filter()
           
 
Method Summary
abstract  boolean accept(Key k, Value v)
           
 SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment env)
          Creates a deep copy of this iterator as though seek had not yet been called.
 OptionDescriber.IteratorOptions describeOptions()
          Gets an iterator options object that contains information needed to configure this iterator.
protected  void findTop()
          Iterates over the source until an acceptable key/value pair is found.
 void init(SortedKeyValueIterator<Key,Value> source, Map<String,String> options, IteratorEnvironment env)
          Initializes the iterator.
 void next()
          Advances to the next K,V pair.
 void seek(Range range, Collection<ByteSequence> columnFamilies, boolean inclusive)
          Seeks to the first key in the Range, restricting the resulting K,V pairs to those with the specified columns.
static void setNegate(IteratorSetting is, boolean negate)
          A convenience method for setting the negation option on a filter.
 boolean validateOptions(Map<String,String> options)
          Check to see if an options map contains all options required by an iterator and that the option values are in the expected formats.
 
Methods inherited from class org.apache.accumulo.core.iterators.WrappingIterator
getSource, getTopKey, getTopValue, hasTop, setSource
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

NEGATE

protected static final String NEGATE
See Also:
Constant Field Values
Constructor Detail

Filter

public Filter()
Method Detail

deepCopy

public SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment env)
Description copied from interface: SortedKeyValueIterator
Creates a deep copy of this iterator as though seek had not yet been called. init should be called on an iterator before deepCopy is called. init should not need to be called on the copy that is returned by deepCopy; that is, when necessary init should be called in the deepCopy method on the iterator it returns. The behavior is unspecified if init is called after deepCopy either on the original or the copy.

Specified by:
deepCopy in interface SortedKeyValueIterator<Key,Value>
Overrides:
deepCopy in class WrappingIterator
Parameters:
env - IteratorEnvironment environment in which iterator is being run.
Returns:
SortedKeyValueIterator a copy of this iterator (with the same source and settings).

next

public void next()
          throws IOException
Description copied from interface: SortedKeyValueIterator
Advances to the next K,V pair. Note that in minor compaction scope and in non-full major compaction scopes the iterator may see deletion entries. These entries should be preserved by all iterators except ones that are strictly scan-time iterators that will never be configured for the minc or majc scopes. Deletion entries are only removed during full major compactions.

Specified by:
next in interface SortedKeyValueIterator<Key,Value>
Overrides:
next in class WrappingIterator
Throws:
IOException - if an I/O error occurs.

seek

public void seek(Range range,
                 Collection<ByteSequence> columnFamilies,
                 boolean inclusive)
          throws IOException
Description copied from interface: SortedKeyValueIterator
Seeks to the first key in the Range, restricting the resulting K,V pairs to those with the specified columns. An iterator does not have to stop at the end of the range. The whole range is provided so that iterators can make optimizations. Seek may be called multiple times with different parameters after SortedKeyValueIterator.init(org.apache.accumulo.core.iterators.SortedKeyValueIterator, java.util.Map, org.apache.accumulo.core.iterators.IteratorEnvironment) is called. Iterators that examine groups of adjacent key/value pairs (e.g. rows) to determine their top key and value should be sure that they properly handle a seek to a key in the middle of such a group (e.g. the middle of a row). Even if the client always seeks to a range containing an entire group (a,c), the tablet server could send back a batch of entries corresponding to (a,b], then reseek the iterator to range (b,c) when the scan is continued. columnFamilies is used, at the lowest level, to determine which data blocks inside of an RFile need to be opened for this iterator. This set of data blocks is also the set of locality groups defined for the given table. If no columnFamilies are provided, the data blocks for all locality groups inside of the correct RFile will be opened and seeked in an attempt to find the correct start key, regardless of the startKey in the range. In an Accumulo instance in which multiple locality groups exist for a table, it is important to ensure that columnFamilies is properly set to the minimum required column families to ensure that data from separate locality groups is not inadvertently read.

Specified by:
seek in interface SortedKeyValueIterator<Key,Value>
Overrides:
seek in class WrappingIterator
Parameters:
range - Range of keys to iterate over.
columnFamilies - Collection of column families to include or exclude.
inclusive - boolean that indicates whether to include (true) or exclude (false) column families.
Throws:
IOException - if an I/O error occurs.

findTop

protected void findTop()
Iterates over the source until an acceptable key/value pair is found.


accept

public abstract boolean accept(Key k,
                               Value v)
Returns:
true if the key/value pair is accepted by the filter.

init

public void init(SortedKeyValueIterator<Key,Value> source,
                 Map<String,String> options,
                 IteratorEnvironment env)
          throws IOException
Description copied from interface: SortedKeyValueIterator
Initializes the iterator. Data should not be read from the source in this method.

Specified by:
init in interface SortedKeyValueIterator<Key,Value>
Overrides:
init in class WrappingIterator
Parameters:
source - SortedKeyValueIterator source to read data from.
options - Map map of string option names to option values.
env - IteratorEnvironment environment in which iterator is being run.
Throws:
IOException - unused.

describeOptions

public OptionDescriber.IteratorOptions describeOptions()
Description copied from interface: OptionDescriber
Gets an iterator options object that contains information needed to configure this iterator. This object will be used by the accumulo shell to prompt the user to input the appropriate information.

Specified by:
describeOptions in interface OptionDescriber
Returns:
an iterator options object

validateOptions

public boolean validateOptions(Map<String,String> options)
Description copied from interface: OptionDescriber
Check to see if an options map contains all options required by an iterator and that the option values are in the expected formats.

Specified by:
validateOptions in interface OptionDescriber
Parameters:
options - a map of option names to option values
Returns:
true if options are valid, false otherwise (IllegalArgumentException preferred)

setNegate

public static void setNegate(IteratorSetting is,
                             boolean negate)
A convenience method for setting the negation option on a filter.

Parameters:
is - IteratorSetting object to configure.
negate - if false, filter accepts k/v for which the accept method returns true; if true, filter accepts k/v for which the accept method returns false.


Copyright © 2013 Apache Accumulo Project. All Rights Reserved.