Package it.unimi.di.big.mg4j.search

Class AndDocumentIterator

java.lang.Object

it.unimi.di.big.mg4j.search.AbstractDocumentIterator

it.unimi.di.big.mg4j.search.AbstractIntervalDocumentIterator

it.unimi.di.big.mg4j.search.AbstractCompositeDocumentIterator

it.unimi.di.big.mg4j.search.AbstractIntersectionDocumentIterator

it.unimi.di.big.mg4j.search.AndDocumentIterator

All Implemented Interfaces:

DocumentIterator

public class AndDocumentIterator
extends AbstractIntersectionDocumentIterator

A document iterator that returns the AND of a number of document iterators.

This class adds to AbstractIntersectionDocumentIterator an interval iterator generating the AND of the intervals returned for each of the documents involved.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected class	AndDocumentIterator.AndIndexIntervalIterator	An interval iterator returning the AND (in the Clarke−Cormack−Burkowski lattice) of the component interval iterators.
protected class	AndDocumentIterator.AndIntervalIterator	An interval iterator returning the AND (in the Clarke−Cormack−Burkowski lattice) of the component interval iterators.

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

AbstractCompositeDocumentIterator.AbstractCompositeIndexIntervalIterator, AbstractCompositeDocumentIterator.AbstractCompositeIntervalIterator

Field Summary

Fields inherited from class it.unimi.di.big.mg4j.search.AbstractIntersectionDocumentIterator

lastIterator, sortedIterator

Fields inherited from class it.unimi.di.big.mg4j.search.AbstractCompositeDocumentIterator

documentIterator, indexIterator, indexIteratorsWithoutPositions, n

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

currentIterators, indices, intervalIterators, soleIndex, soleIntervalIterator, unmodifiableCurrentIterators

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

curr, weight

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

END_OF_LIST

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AndDocumentIterator(DocumentIterator[] documentIterator)

Method Summary

Modifier and Type	Method	Description
static DocumentIterator	getInstance(Index index, DocumentIterator... documentIterator)	Returns a document iterator that computes the AND of the given array of iterators.
static DocumentIterator	getInstance(DocumentIterator... documentIterator)	Returns a document iterator that computes the AND of the given nonzero-length array of iterators.
protected IntervalIterator	getIntervalIterator(Index index, int n, boolean allIndexIterators, Object unused)	Creates an interval iterator suitable for this AbstractIntervalDocumentIterator.
IntervalIterator	intervalIterator()	Returns the interval iterator of this document iterator for single-index queries.
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.
long	nextDocument()	Returns the next document provided by this document iterator, or DocumentIterator.END_OF_LIST if no more documents are available.
long	skipTo(long n)	Skips all documents smaller than n.

Methods inherited from class it.unimi.di.big.mg4j.search.AbstractIntersectionDocumentIterator

align

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

accept, acceptOnTruePaths, dispose, toString

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

allIndexIterators, indices, indices

Methods inherited from class it.unimi.di.big.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.big.mg4j.search.DocumentIterator

document, indices, mayHaveNext, weight, weight

Constructor Detail

AndDocumentIterator

protected AndDocumentIterator(DocumentIterator[] documentIterator)

Method Detail

getInstance

public static DocumentIterator getInstance(Index index,
                                           DocumentIterator... documentIterator)

Returns a document iterator that computes the AND of the given array of iterators.

Note that the special case of the empty and of the singleton arrays are handled efficiently.

Parameters:

index - the default index; relevant only if documentIterator has zero length.

documentIterator - the iterators to be joined.

Returns:

a document iterator that computes the AND of documentIterator.

getInstance

public static DocumentIterator getInstance(DocumentIterator... documentIterator)

Returns a document iterator that computes the AND of the given nonzero-length array of iterators.

Note that the special case of the singleton array is handled efficiently.

Parameters:

documentIterator - the iterators to be joined (at least one).

Returns:

a document iterator that computes the AND of documentIterator.

getIntervalIterator

protected IntervalIterator getIntervalIterator(Index index,
                                               int n,
                                               boolean allIndexIterators,
                                               Object unused)

Description copied from class: AbstractIntervalDocumentIterator

Creates an interval iterator suitable for this AbstractIntervalDocumentIterator.

Specified by:

getIntervalIterator in class AbstractIntervalDocumentIterator

Parameters:

index - the reference index for the iterator, or null.

n - the number of underlying or component iterators.

allIndexIterators - whether all underlying or component iterators are index iterators.

unused - an optional argument.

Returns:

an interval iterator suitable for this AbstractIntervalDocumentIterator.

skipTo

public long skipTo(long 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 long 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

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).

Specified by:

intervalIterators in interface DocumentIterator

Overrides:

intervalIterators in class AbstractIntersectionDocumentIterator

Returns:

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

Throws:

IOException

See Also:

DocumentIterator.intervalIterator(Index)

intervalIterator

public IntervalIterator intervalIterator()
                                  throws IOException

Description copied from interface: DocumentIterator

Returns the interval iterator of this document iterator for single-index queries.

This is a commodity method that can be used only for queries built over a single index.

Returns:

an interval iterator.

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