public class CachingDocumentIterator extends Object implements DocumentIterator
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
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the one previously returned is no longer valid, and when the current document changes (e.g.,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.
|Constructor and Description|
|Modifier and Type||Method and Description|
Accepts a visitor.
Accepts a visitor after a call to
Disposes this document iterator, releasing all resources.
Returns the last document returned by
Returns the set of indices over which this iterator is built.
Returns the interval iterator of this document iterator for single-index queries.
Returns the interval iterator of this document iterator for the given index.
Returns an unmodifiable map from indices to interval iterators.
Returns whether there may be a next document, possibly with false positives.
Returns the next document provided by this document iterator, or
Skips all documents smaller than
Returns the weight associated with this iterator.
Sets the weight of this index iterator.
public CachingDocumentIterator(DocumentIterator documentIterator)
public int document()
public ReferenceSet<Index> indices()
public IntervalIterator intervalIterator(Index index) throws IOException
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
Thus, in presence of indices without positions it is possible that no
intervals at all are available.
public IntervalIterator intervalIterator() throws IOException
This is a commodity method that can be used only for queries built over a single index.
public Reference2ReferenceMap<Index,IntervalIterator> intervalIterators() throws IOException
After a call to
DocumentIterator.nextDocument(), this map
can be used to retrieve the intervals in the current document. An invocation of
on this map with argument
index yields the same result as
public int nextDocument() throws IOException
DocumentIterator.END_OF_LISTif no more documents are available.
public boolean mayHaveNext()
public int skipTo(int n) throws IOException
Define the current document
k associated with this document iterator
DocumentIterator.nextDocument()and this method have never been called;
DocumentIterator.END_OF_LIST, if a call to this method or to
DocumentIterator.nextDocument()or this method, otherwise.
k is larger than or equal to
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
is returned, the state of this iterator
will be exactly the same as after a call to
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
public void dispose() throws IOException
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.
public <T> T accept(DocumentIteratorVisitor<T> visitor) throws IOException
A document iterator is usually structured as composite,
with operators as internal nodes and
as leaves. This method implements the visitor pattern.
public <T> T acceptOnTruePaths(DocumentIteratorVisitor<T> visitor) throws IOException
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
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
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
public IntervalIterator iterator()
public double weight()
The number returned by this method has no fixed semantics: different scorers might choose different interpretations, or even ignore it.