org.apache.accumulo.core.iterators.user

Class IntersectingIterator

java.lang.Object

org.apache.accumulo.core.iterators.user.IntersectingIterator

All Implemented Interfaces:

SortedKeyValueIterator<Key,Value>

Direct Known Subclasses:

IndexedDocIterator, IntersectingIterator

public class IntersectingIterator
extends Object
implements SortedKeyValueIterator<Key,Value>

This iterator facilitates document-partitioned indexing. It involves grouping a set of documents together and indexing those documents into a single row of an Accumulo table. This allows a tablet server to perform boolean AND operations on terms in the index. The table structure should have the following form: row: shardID, colfam: term, colqual: docID When you configure this iterator with a set of terms (column families), it will return only the docIDs that appear with all of the specified terms. The result will have an empty column family, as follows: row: shardID, colfam: (empty), colqual: docID This iterator is commonly used with BatchScanner or AccumuloInputFormat, to parallelize the search over all shardIDs. This iterator will *ignore* any columnFamilies passed to seek(Range, Collection, boolean) as it performs intersections over terms. Extending classes should override the IntersectingIterator.TermSource.seekColfams in their implementation's init(SortedKeyValueIterator, Map, IteratorEnvironment) method. README.shard in docs/examples shows an example of using the IntersectingIterator.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	IntersectingIterator.TermSource

Field Summary

Fields

Modifier and Type	Field and Description
protected org.apache.hadoop.io.Text	currentDocID
protected org.apache.hadoop.io.Text	currentPartition
protected static org.apache.log4j.Logger	log
protected org.apache.hadoop.io.Text	nullText
protected IntersectingIterator.TermSource[]	sources
protected Key	topKey
protected Value	value

Constructor Summary

Constructors

Constructor and Description
IntersectingIterator()

Method Summary

Methods

Modifier and Type	Method and Description
void	addSource(SortedKeyValueIterator<Key,Value> source, IteratorEnvironment env, org.apache.hadoop.io.Text term, boolean notFlag)
protected void	advanceToIntersection()
protected Key	buildFollowingPartitionKey(Key key)
protected Key	buildKey(org.apache.hadoop.io.Text partition, org.apache.hadoop.io.Text term)
protected Key	buildKey(org.apache.hadoop.io.Text partition, org.apache.hadoop.io.Text term, org.apache.hadoop.io.Text docID)
protected static boolean[]	decodeBooleans(String flags)
protected static org.apache.hadoop.io.Text[]	decodeColumns(String columns)
SortedKeyValueIterator<Key,Value>	deepCopy(IteratorEnvironment env) Creates a deep copy of this iterator as though seek had not yet been called.
protected static String	encodeBooleans(boolean[] flags)
protected static String	encodeColumns(org.apache.hadoop.io.Text[] columns)
protected org.apache.hadoop.io.Text	getDocID(Key key)
protected org.apache.hadoop.io.Text	getPartition(Key key)
protected org.apache.hadoop.io.Text	getTerm(Key key)
Key	getTopKey() Returns top key.
Value	getTopValue() Returns top value.
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> seekColumnFamilies, boolean inclusive) Seeks to the first key in the Range, restricting the resulting K,V pairs to those with the specified columns.
static void	setColumnFamilies(IteratorSetting cfg, org.apache.hadoop.io.Text[] columns) Encode the columns to be used when iterating.
static void	setColumnFamilies(IteratorSetting cfg, org.apache.hadoop.io.Text[] columns, boolean[] notFlags) Encode columns and NOT flags indicating which columns should be negated (docIDs will be excluded if matching negated columns, instead of included).
static String	stringTopKey(SortedKeyValueIterator<Key,Value> iter)

Methods inherited from class java.lang.Object

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

Field Detail

nullText

protected org.apache.hadoop.io.Text nullText

log

protected static final org.apache.log4j.Logger log

sources

protected IntersectingIterator.TermSource[] sources

currentPartition

protected org.apache.hadoop.io.Text currentPartition

currentDocID

protected org.apache.hadoop.io.Text currentDocID

topKey

protected Key topKey

value

protected Value value

Constructor Detail

IntersectingIterator

public IntersectingIterator()

Method Detail

getPartition

protected org.apache.hadoop.io.Text getPartition(Key key)

getTerm

protected org.apache.hadoop.io.Text getTerm(Key key)

getDocID

protected org.apache.hadoop.io.Text getDocID(Key key)

buildKey

protected Key buildKey(org.apache.hadoop.io.Text partition,
           org.apache.hadoop.io.Text term)

buildKey

protected Key buildKey(org.apache.hadoop.io.Text partition,
           org.apache.hadoop.io.Text term,
           org.apache.hadoop.io.Text docID)

buildFollowingPartitionKey

protected Key buildFollowingPartitionKey(Key key)

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>

Parameters:

env - IteratorEnvironment environment in which iterator is being run.

Returns:

SortedKeyValueIterator a copy of this iterator (with the same source and settings).

getTopKey

public Key getTopKey()

Description copied from interface: SortedKeyValueIterator

Returns top key. Can be called 0 or more times without affecting behavior of next() or hasTop(). 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:

getTopKey in interface SortedKeyValueIterator<Key,Value>

Returns:

K

getTopValue

public Value getTopValue()

Description copied from interface: SortedKeyValueIterator

Returns top value. Can be called 0 or more times without affecting behavior of next() or hasTop().

Specified by:

getTopValue in interface SortedKeyValueIterator<Key,Value>

Returns:

V

hasTop

public boolean hasTop()

Description copied from interface: SortedKeyValueIterator

Returns true if the iterator has more elements.

Specified by:

hasTop in interface SortedKeyValueIterator<Key,Value>

Returns:

true if the iterator has more elements.

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>

Throws:

IOException - if an I/O error occurs.

advanceToIntersection

protected void advanceToIntersection()
                              throws IOException

Throws:

IOException

stringTopKey

public static String stringTopKey(SortedKeyValueIterator<Key,Value> iter)

encodeColumns

protected static String encodeColumns(org.apache.hadoop.io.Text[] columns)

Returns:

encoded columns

encodeBooleans

protected static String encodeBooleans(boolean[] flags)

Returns:

encoded flags

decodeColumns

protected static org.apache.hadoop.io.Text[] decodeColumns(String columns)

decodeBooleans

protected static boolean[] decodeBooleans(String flags)

Returns:

decoded flags

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>

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.

seek

public void seek(Range range,
        Collection<ByteSequence> seekColumnFamilies,
        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>

Parameters:

range - Range of keys to iterate over.

seekColumnFamilies - 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.

addSource

public void addSource(SortedKeyValueIterator<Key,Value> source,
             IteratorEnvironment env,
             org.apache.hadoop.io.Text term,
             boolean notFlag)

setColumnFamilies

public static void setColumnFamilies(IteratorSetting cfg,
                     org.apache.hadoop.io.Text[] columns)

Encode the columns to be used when iterating.

setColumnFamilies

public static void setColumnFamilies(IteratorSetting cfg,
                     org.apache.hadoop.io.Text[] columns,
                     boolean[] notFlags)

Encode columns and NOT flags indicating which columns should be negated (docIDs will be excluded if matching negated columns, instead of included).