it.unimi.dsi.mg4j.search
Class AbstractUnionDocumentIterator

java.lang.Object
  it.unimi.dsi.fastutil.ints.AbstractIntIterator
      it.unimi.dsi.mg4j.search.AbstractDocumentIterator
          it.unimi.dsi.mg4j.search.AbstractCompositeDocumentIterator
              it.unimi.dsi.mg4j.search.AbstractUnionDocumentIterator

All Implemented Interfaces:

IntIterator, DocumentIterator, Iterable<Interval>, Iterator<Integer>

Direct Known Subclasses:

MultiTermIndexIterator, OrDocumentIterator

public abstract class AbstractUnionDocumentIterator
extends AbstractCompositeDocumentIterator

A document iterator on documents, generating the union of the documents returned by a number of document iterators.

The pattern of this class is the same as that of AbstractIntersectionDocumentIterator. Additionally, this class provides a mechanism that makes accessible the set of component document iterators that are positioned on the current document.

Nested Class Summary

Nested classes/interfaces inherited from class it.unimi.dsi.mg4j.search.AbstractCompositeDocumentIterator

AbstractCompositeDocumentIterator.AbstractCompositeIndexIntervalIterator, AbstractCompositeDocumentIterator.AbstractCompositeIntervalIterator

Nested classes/interfaces inherited from class it.unimi.dsi.mg4j.search.AbstractDocumentIterator

AbstractDocumentIterator.AbstractIntervalIterator

Field Summary

protected int[]	front The IndirectPriorityQueue.front(int[]) of queue, if frontSize is not -1.
protected int	frontSize The number of valid entries in front, or -1 if the front has not been computed for the current document.
protected IntHeapSemiIndirectPriorityQueue	queue A heap-based semi-indirect priority queue used to keep track of the currently scanned integers.
protected int[]	refArray The reference array used for the queue.

Fields inherited from class it.unimi.dsi.mg4j.search.AbstractCompositeDocumentIterator

documentIterator, indexIterator, indices, n, soleIndex

Fields inherited from class it.unimi.dsi.mg4j.search.AbstractDocumentIterator

ahead, curr, weight

Fields inherited from interface it.unimi.dsi.mg4j.search.DocumentIterator

END_OF_LIST

Constructor Summary

protected

AbstractUnionDocumentIterator(DocumentIterator... documentIterator) Creates a new document iterator that computes the OR of the given array of iterators.

Method Summary

<T> T	acceptOnTruePaths(DocumentIteratorVisitor<T> visitor) Invokes acceptOnTruePaths(DocumentIteratorVisitor) only on component iterators positioned on the current document.
protected int	computeFront() Forces computation of the current front, returning the number of indices it contains.
protected abstract IntervalIterator	getComposedIntervalIterator(Index index)
IntervalIterator	intervalIterator(Index index) Returns the interval iterator of this document iterator for the given index.
Reference2ReferenceMap<Index,IntervalIterator>	intervalIterators() Returns an unmodifiable map from indices to interval iterators.
protected int	nextDocumentInternal()
int	skipTo(int n) Skips all documents smaller than n.

Methods inherited from class it.unimi.dsi.mg4j.search.AbstractCompositeDocumentIterator

accept, dispose, indices, intervalIterator, toString

Methods inherited from class it.unimi.dsi.mg4j.search.AbstractDocumentIterator

document, ensureOnADocument, fromNextDocument, hasNext, iterator, nextDocument, nextInt, toNextDocument, weight, weight

Methods inherited from class it.unimi.dsi.fastutil.ints.AbstractIntIterator

next, remove, skip

Methods inherited from class java.lang.Object

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

Methods inherited from interface it.unimi.dsi.mg4j.search.DocumentIterator

document, iterator, nextDocument, nextInt, weight, weight

Methods inherited from interface it.unimi.dsi.fastutil.ints.IntIterator

skip

Methods inherited from interface java.util.Iterator

hasNext, next, remove

Field Detail

queue

protected final IntHeapSemiIndirectPriorityQueue queue

A heap-based semi-indirect priority queue used to keep track of the currently scanned integers.

front

protected final int[] front

The IndirectPriorityQueue.front(int[]) of queue, if frontSize is not -1.

refArray

protected final int[] refArray

The reference array used for the queue.

frontSize

protected int frontSize

The number of valid entries in front, or -1 if the front has not been computed for the current document.

Constructor Detail

AbstractUnionDocumentIterator

protected AbstractUnionDocumentIterator(DocumentIterator... documentIterator)
                                 throws IOException

Creates a new document iterator that computes the OR of the given array of iterators.

Parameters:

documentIterator - the iterators to be joined.

Throws:

IOException

Method Detail

skipTo

public int skipTo(int n)
           throws IOException

Description copied from interface: DocumentIterator

Skips all documents smaller than n. If Iterator.hasNext() has been called returning true but DocumentIterator.nextDocument() has not been called afterwards, then a call to DocumentIterator.skipTo(int) will be implicitly preceded by a call to DocumentIterator.nextDocument() (the only consequence is that skipping to the current document after a call to Iterator.hasNext() will return the next document).

Define the current document k associated with this document iterator as follows:

• -1, if DocumentIterator.nextDocument() and this method have never been called;
• DocumentIterator.END_OF_LIST, if a call to this method returned DocumentIterator.END_OF_LIST, or DocumentIterator.nextDocument() returned -1;
• the last value returned by a call to DocumentIterator.nextDocument() or this method, otherwise.

If k is larger than or equal to n, then this method does nothing and returns k. Otherwise, a call to this method is equivalent to

 while( ( k = nextDocument() ) < n && k != -1 );
 return k == -1 ? END_OF_LIST : k;
 

Thus, when a result k ≠ DocumentIterator.END_OF_LIST is returned, the state of this iterator will be exactly the same as after a call to DocumentIterator.nextDocument() that returned k. In particular, the first document larger than or equal to n (when returned by this method) will not be returned by the next call to DocumentIterator.nextDocument().

Parameters:

n - a document pointer.

Returns:

a document pointer larger than or equal to n if available, DocumentIterator.END_OF_LIST otherwise.

Throws:

IOException

nextDocumentInternal

protected int nextDocumentInternal()
                            throws IOException

Specified by:

nextDocumentInternal in class AbstractDocumentIterator

Throws:

IOException

computeFront

protected int computeFront()

Forces computation of the current front, returning the number of indices it contains.

After a call to this method, the first elements of front contain the indices of the component document iterators that are positioned on the current document. If the front has already been computed for the current document, this method has no side effects.

Returns:

the size of the current front (the number of valid entries in front).

intervalIterators

public Reference2ReferenceMap<Index,IntervalIterator> intervalIterators()
                                                                 throws IOException

Description copied from interface: DocumentIterator

Returns an unmodifiable map from indices to interval iterators.

After a call to DocumentIterator.nextDocument(), this map can be used to retrieve the intervals in the current document. An invocation of Map.get(java.lang.Object) on this map with argument index yields the same result as intervalIterator(index).

Returns:

a map from indices to interval iterators over the current document.

Throws:

IOException

See Also:

DocumentIterator.intervalIterator(Index)

intervalIterator

public IntervalIterator intervalIterator(Index index)
                                  throws IOException

Description copied from interface: DocumentIterator

Returns the interval iterator of this document iterator for the given index.

After a call to DocumentIterator.nextDocument(), this iterator can be used to retrieve the intervals in the current document (the one returned by DocumentIterator.nextDocument()) for the index index.

Note that if all indices have positions, it is guaranteed that at least one index will return an interval. However, for disjunctive queries it cannot be guaranteed that all indices will return an interval.

Indices without positions always return IntervalIterators.TRUE. Thus, in presence of indices without positions it is possible that no intervals at all are available.

Parameters:

index - an index (must be one over which the query was built).

Returns:

an interval iterator over the current document in index.

Throws:

IOException

getComposedIntervalIterator

protected abstract IntervalIterator getComposedIntervalIterator(Index index)

acceptOnTruePaths

public <T> T acceptOnTruePaths(DocumentIteratorVisitor<T> visitor)
                    throws IOException

Invokes acceptOnTruePaths(DocumentIteratorVisitor) only on component iterators positioned on the current document.

Specified by:

acceptOnTruePaths in interface DocumentIterator

Overrides:

acceptOnTruePaths in class AbstractCompositeDocumentIterator

Parameters:

visitor - a visitor.

Returns:

true if the visit should continue.

Throws:

IOException

See Also:

DocumentIterator.accept(DocumentIteratorVisitor), CounterCollectionVisitor