it.unimi.di.mg4j.index.cluster
Class DocumentalConcatenatedClusterDocumentIterator

java.lang.Object
  extended by it.unimi.di.mg4j.search.AbstractDocumentIterator
      extended by it.unimi.di.mg4j.index.cluster.DocumentalConcatenatedClusterDocumentIterator
All Implemented Interfaces:
DocumentIterator
Direct Known Subclasses:
DocumentalConcatenatedClusterIndexIterator

public class DocumentalConcatenatedClusterDocumentIterator
extends AbstractDocumentIterator
implements DocumentIterator

A document iterator concatenating iterators from local indices.

Author:
Alessandro Arrabito, Sebastiano Vigna

Field Summary
protected  int currentIterator
          The current iterator (an index into documentIterator).
protected  DocumentIterator[] documentIterator
          The component document iterators.
protected  int[] documentIteratorIndex
          The indices corresponding to each underlying document iterator.
protected  int lastIterator
          The last iterator to ever return something (an index into documentIterator).
protected  int n
          The number of component iterators.
protected  ContiguousDocumentalStrategy strategy
          The cached strategy of the index we refer to.
 
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
DocumentalConcatenatedClusterDocumentIterator(DocumentalClusterIndexReader indexReader, DocumentIterator[] documentIterator, int[] usedIndex)
          Creates a new document iterator for a documental cluster.
 
Method Summary
<T> T
accept(DocumentIteratorVisitor<T> visitor)
          Accepts a visitor.
<T> T
acceptOnTruePaths(DocumentIteratorVisitor<T> visitor)
          Accepts a visitor after a call to DocumentIterator.nextDocument(), limiting recursion to true paths.
 void dispose()
          Disposes this document iterator, releasing all resources.
 ReferenceSet<Index> indices()
          Returns the set of indices over which this iterator is built.
 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.
 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 p)
          Skips all documents smaller than n.
 String toString()
           
 
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, mayHaveNext, weight, weight
 

Field Detail

documentIterator

protected final DocumentIterator[] documentIterator
The component document iterators.


n

protected final int n
The number of component iterators.


documentIteratorIndex

protected final int[] documentIteratorIndex
The indices corresponding to each underlying document iterator.


strategy

protected final ContiguousDocumentalStrategy strategy
The cached strategy of the index we refer to.


currentIterator

protected int currentIterator
The current iterator (an index into documentIterator). If it is equal to n, it means that we hit the end of list on the last document iterator. Otherwise, AbstractDocumentIterator.curr contains the last document ever returned or reached by skipTo(int).


lastIterator

protected int lastIterator
The last iterator to ever return something (an index into documentIterator).

Constructor Detail

DocumentalConcatenatedClusterDocumentIterator

public DocumentalConcatenatedClusterDocumentIterator(DocumentalClusterIndexReader indexReader,
                                                     DocumentIterator[] documentIterator,
                                                     int[] usedIndex)
Creates a new document iterator for a documental cluster.

This constructor uses an array of document iterators that it is not required to be full. This is very useful with rare terms.

Parameters:
indexReader - the underlying index reader.
documentIterator - an array of document iterators.
usedIndex - an array parallel to documentIterator containing the number of the indices corresponding to the iterators.
Method Detail

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.

Specified by:
intervalIterator in interface DocumentIterator
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.

Specified by:
intervalIterator in interface DocumentIterator
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

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
Returns:
a map from indices to interval iterators over the current document.
Throws:
IOException
See Also:
DocumentIterator.intervalIterator(Index)

indices

public ReferenceSet<Index> indices()
Description copied from interface: DocumentIterator
Returns the set of indices over which this iterator is built.

Specified by:
indices in interface DocumentIterator
Returns:
the set of indices over which this iterator is built.

skipTo

public int skipTo(int p)
           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:

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 kDocumentIterator.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().

Specified by:
skipTo in interface DocumentIterator
Parameters:
p - 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.

Specified by:
nextDocument in interface DocumentIterator
Returns:
the next document, or DocumentIterator.END_OF_LIST if no more documents are available.
Throws:
IOException

accept

public <T> T accept(DocumentIteratorVisitor<T> visitor)
         throws IOException
Description copied from interface: DocumentIterator
Accepts a visitor.

A document iterator is usually structured as composite, with operators as internal nodes and IndexIterators as leaves. This method implements the visitor pattern.

Specified by:
accept in interface DocumentIterator
Parameters:
visitor - the visitor.
Returns:
an object resulting from the visit, or null if the visit was interrupted.
Throws:
IOException

acceptOnTruePaths

public <T> T acceptOnTruePaths(DocumentIteratorVisitor<T> visitor)
                    throws IOException
Description copied from interface: DocumentIterator
Accepts a visitor after a call to DocumentIterator.nextDocument(), limiting recursion to true paths.

After a call to DocumentIterator.nextDocument(), a document iterator is positioned over a document. This call is equivalent to DocumentIterator.accept(DocumentIteratorVisitor), but visits only along true paths.

We define a true path as a path from the root of the composite that passes only through nodes whose associated subtree is positioned on the same document of the root. Note that OrDocumentIterators detach exhausted iterators from the composite tree, so true paths define the subtree that is causing the current document to satisfy the query represented by this document iterator.

For more elaboration, and the main application of this method, see CounterCollectionVisitor.

Specified by:
acceptOnTruePaths in interface DocumentIterator
Parameters:
visitor - the visitor.
Returns:
an object resulting from the visit, or null if the visit was interrupted.
Throws:
IOException
See Also:
DocumentIterator.accept(DocumentIteratorVisitor), CounterCollectionVisitor

dispose

public void dispose()
             throws IOException
Description copied from interface: DocumentIterator
Disposes this document iterator, releasing all resources.

This method should propagate down to the underlying index iterators, where it should release resources such as open files and network connections. If you're doing your own resource tracking and pooling, then you do not need to call this method.

Specified by:
dispose in interface DocumentIterator
Throws:
IOException

toString

public String toString()
Overrides:
toString in class Object