it.unimi.di.mg4j.search
Class AbstractUnionDocumentIterator

java.lang.Object
  it.unimi.di.mg4j.search.AbstractDocumentIterator
      it.unimi.di.mg4j.search.AbstractIntervalDocumentIterator
          it.unimi.di.mg4j.search.AbstractCompositeDocumentIterator
              it.unimi.di.mg4j.search.AbstractUnionDocumentIterator

All Implemented Interfaces:

DocumentIterator

Direct Known Subclasses:

MultiTermIndexIterator, OrDocumentIterator

public abstract class AbstractUnionDocumentIterator
extends AbstractCompositeDocumentIterator

A document iterator computing the union of the documents returned by a number of document iterators.

This class provides a mechanism that makes accessible the set of component document iterators that are positioned on the current document.

Nested Class Summary

protected static class

AbstractUnionDocumentIterator.IntHeapSemiIndirectPriorityQueue

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

AbstractCompositeDocumentIterator.AbstractCompositeIndexIntervalIterator, AbstractCompositeDocumentIterator.AbstractCompositeIntervalIterator

Field Summary

int[]	front The AbstractUnionDocumentIterator.IntHeapSemiIndirectPriorityQueue.front(int[]) of queue, if frontSize is not 0.
protected int	frontSize The number of valid entries in front, or 0 if the front has not been computed for the current document.
protected AbstractUnionDocumentIterator.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.di.mg4j.search.AbstractCompositeDocumentIterator

documentIterator, indexIterator, indexIteratorsWithoutPositions, n

Fields inherited from class it.unimi.di.mg4j.search.AbstractIntervalDocumentIterator

currentIterators, indices, intervalIterators, soleIndex, soleIntervalIterator, unmodifiableCurrentIterators

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

curr, weight

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

END_OF_LIST

Constructor Summary

protected

AbstractUnionDocumentIterator(DocumentIterator... documentIterator)

Method Summary

<T> T	acceptOnTruePaths(DocumentIteratorVisitor<T> visitor) Invokes acceptOnTruePaths(DocumentIteratorVisitor) only on component iterators positioned on the current document.
int	computeFront() Forces computation of the current front, returning the number of indices it contains.
Reference2ReferenceMap<Index,IntervalIterator>	intervalIterators() Returns an unmodifiable map from indices to interval iterators.
int	nextDocument() Returns the next document provided by this document iterator, or DocumentIterator.END_OF_LIST if no more documents are available.
int	skipTo(int n) Skips all documents smaller than n.

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

accept, dispose, toString

Methods inherited from class it.unimi.di.mg4j.search.AbstractIntervalDocumentIterator

allIndexIterators, getIntervalIterator, indices, indices

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

document, ensureOnADocument, mayHaveNext, weight, weight

Methods inherited from class java.lang.Object

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

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

document, indices, intervalIterator, intervalIterator, mayHaveNext, weight, weight

Field Detail

queue

protected final AbstractUnionDocumentIterator.IntHeapSemiIndirectPriorityQueue queue

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

front

public final int[] front

The AbstractUnionDocumentIterator.IntHeapSemiIndirectPriorityQueue.front(int[]) of queue, if frontSize is not 0.

refArray

protected final int[] refArray

The reference array used for the queue.

frontSize

protected int frontSize

The number of valid entries in front, or 0 if the front has not been computed for the current document.

Constructor Detail

AbstractUnionDocumentIterator

protected AbstractUnionDocumentIterator(DocumentIterator... documentIterator)
                                 throws IOException

Throws:

IOException

Method Detail

skipTo

public int skipTo(int n)
           throws IOException

Description copied from interface: DocumentIterator

Skips all documents smaller than n.

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 or to DocumentIterator.nextDocument() returned DocumentIterator.END_OF_LIST;
• 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 );
 return 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

nextDocument

public int nextDocument()
                 throws IOException

Description copied from interface: DocumentIterator

Returns the next document provided by this document iterator, or DocumentIterator.END_OF_LIST if no more documents are available.

Returns:

the next document, or DocumentIterator.END_OF_LIST if no more documents are available.

Throws:

IOException

computeFront

public 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)

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