java.lang.Object
- it.unimi.di.big.mg4j.search.CachingDocumentIterator

All Implemented Interfaces:

DocumentIterator
```
public class CachingDocumentIterator
extends Object
implements DocumentIterator
```
A decorator that caches the intervals produced by the underlying document iterator.
Often, scores exhaust the intervals produced by a document iterator to compute their result. However, often you also need those intervals for other purposes (maybe just because you are aggregating several interval-based scorers). Decorating a document iterator with an instance of this class you get again a document iterator, but its intervals can be retrieved several times by calling intervalIterator(Index), intervalIterator() and intervalIterators(). Important: calls are not nestable: when you require again an iterator, the one previously returned is no longer valid, and when the current document changes (e.g., because of a call to nextDocument()) the previously returned interval iterators are invalidated.

Since:

0.9.1

Author:

Sebastiano Vigna

Field Summary
- Fields inherited from interface it.unimi.di.big.mg4j.search.DocumentIterator
  END_OF_LIST

Constructor Summary

Constructors
Constructor Description

CachingDocumentIterator(DocumentIterator documentIterator)

Method Summary

Modifier and Type	Method	Description
`<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.
`long`	`document()`	Returns the last document returned by `DocumentIterator.nextDocument()`.
`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.
`IntervalIterator`	`iterator()`
`boolean`	`mayHaveNext()`	Returns whether there may be a next document, possibly with false positives.
`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`.
`double`	`weight()`	Returns the weight associated with this iterator.
`DocumentIterator`	`weight(double weight)`	Sets the weight of this index iterator.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - CachingDocumentIterator
```
public CachingDocumentIterator(DocumentIterator documentIterator)
```
- Method Detail
  - document
```
public long document()
```
    Description copied from interface: DocumentIterator
    
    Returns the last document returned by DocumentIterator.nextDocument().
    
    Specified by:
    
    document in interface DocumentIterator
    
    Returns:
    
    the last document returned by DocumentIterator.nextDocument(), -1 if no document has been returned yet, and DocumentIterator.END_OF_LIST if the list of results has been exhausted.
  - 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.
  - 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
  - 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)
  - 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)
  - 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.
    
    Specified by:
    
    nextDocument in interface DocumentIterator
    
    Returns:
    
    the next document, or DocumentIterator.END_OF_LIST if no more documents are available.
    
    Throws:
    
    IOException
  - mayHaveNext
```
public boolean mayHaveNext()
```
    Description copied from interface: DocumentIterator
    
    Returns whether there may be a next document, possibly with false positives.
    
    Specified by:
    
    mayHaveNext in interface DocumentIterator
    
    Returns:
    
    true there may be a next document; false if certainly there is no next document.
  - 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().
    Specified by:
    
    skipTo in interface DocumentIterator
    
    Parameters:
    
    n - a document pointer.
    
    Returns:
    
    a document pointer larger than or equal to n if available, DocumentIterator.END_OF_LIST otherwise.
    
    Throws:
    
    IOException
  - 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
  - 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
  - iterator
```
public IntervalIterator iterator()
```
  - weight
```
public double weight()
```
    Description copied from interface: DocumentIterator
    
    Returns the weight associated with this iterator.
    The number returned by this method has no fixed semantics: different scorers might choose different interpretations, or even ignore it.
    
    Specified by:
    
    weight in interface DocumentIterator
    
    Returns:
    
    the weight associated with this iterator.
  - weight
```
public DocumentIterator weight(double weight)
```
    Description copied from interface: DocumentIterator
    
    Sets the weight of this index iterator.
    
    Specified by:
    
    weight in interface DocumentIterator
    
    Parameters:
    
    weight - the weight of this index iterator.
    
    Returns:
    
    this document iterator.

Class CachingDocumentIterator

Field Summary

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

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

CachingDocumentIterator

Method Detail

document

indices

intervalIterator

intervalIterator

intervalIterators

nextDocument

mayHaveNext

skipTo

dispose

accept

acceptOnTruePaths

iterator

weight

weight