org.apache.accumulo.core.iterators.user

Class SeekingFilter

java.lang.Object

org.apache.accumulo.core.iterators.WrappingIterator

org.apache.accumulo.core.iterators.user.SeekingFilter

All Implemented Interfaces:

SortedKeyValueIterator<Key,Value>, YieldingKeyValueIterator<Key,Value>

Direct Known Subclasses:

CfCqSliceSeekingFilter

public abstract class SeekingFilter
extends WrappingIterator

Base class for filters that can skip over key-value pairs which do not match their filter predicate. In addition to returning true/false to accept or reject a kv pair, subclasses can return an extra field which indicates how far the source iterator should be advanced. Note that the behaviour of the negate option is different from the Filter class. If a KV pair fails the subclass' filter predicate and negate is true, then the KV pair will pass the filter. However if the subclass advances the source past a bunch of KV pairs, all those pairs will be implicitly rejected and negate will have no effect.

See Also:

Filter

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SeekingFilter.AdvanceResult
static class	SeekingFilter.FilterResult

Field Summary

Fields

Modifier and Type	Field and Description
protected static String	NEGATE

Constructor Summary

Constructors

Constructor and Description
SeekingFilter()

Method Summary

Modifier and Type	Method and Description
SortedKeyValueIterator<Key,Value>	deepCopy(IteratorEnvironment env) Creates a deep copy of this iterator as though seek had not yet been called.
abstract SeekingFilter.FilterResult	filter(Key k, Value v) Subclasses must provide an implementation which examines the given key and value and determines (1) whether to accept the KV pair and (2) how far to advance the source iterator past the key.
protected void	findTop()
abstract Key	getNextKeyHint(Key k, Value v) Whenever the subclass returns AdvanceResult.USE_HINT from its filter predicate, this method will be called to see how far to advance the source iterator.
boolean	hasTop() Returns true if the iterator has more elements.
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.

Methods inherited from class org.apache.accumulo.core.iterators.WrappingIterator

getSource, getTopKey, getTopValue, setSource

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.accumulo.core.iterators.YieldingKeyValueIterator

enableYielding

Field Detail

NEGATE

protected static final String NEGATE

See Also:

Constant Field Values

Constructor Detail

SeekingFilter

public SeekingFilter()

Method Detail

filter

public abstract SeekingFilter.FilterResult filter(Key k,
                                                  Value v)

Subclasses must provide an implementation which examines the given key and value and determines (1) whether to accept the KV pair and (2) how far to advance the source iterator past the key.

Parameters:

k - a key

v - a value

Returns:

indicating whether to pass or block the key, and how far the source iterator should be advanced.

getNextKeyHint

public abstract Key getNextKeyHint(Key k,
                                   Value v)

Whenever the subclass returns AdvanceResult.USE_HINT from its filter predicate, this method will be called to see how far to advance the source iterator. The return value must be a key which is greater than (sorts after) the input key. If the subclass never returns USE_HINT, this method will never be called and may safely return null.

Parameters:

k - a key

v - a value

Returns:

as above

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.

hasTop

public boolean hasTop()

Description copied from interface: SortedKeyValueIterator

Returns true if the iterator has more elements. Note that if this iterator has yielded (@see YieldingKeyValueIterator.enableYielding(YieldCallback)), this this method must return false.

Specified by:

hasTop in interface SortedKeyValueIterator<Key,Value>

Overrides:

hasTop in class WrappingIterator

Returns:

true if the iterator has more elements.

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<K, V>, java.util.Map<java.lang.String, java.lang.String>, 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.

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.

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. A proper implementation would call deepCopy on the source.

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).

findTop

protected void findTop()
                throws IOException

Throws:

IOException