it.unimi.dsi.fastutil.ints.AbstractIntIterator
it.unimi.dsi.mg4j.search.DocumentIterators.EmptyDocumentIterator
|
|||||||||
| PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||
| SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD | ||||||||
java.lang.Object
protected static class DocumentIterators.EmptyDocumentIterator
An empty document iterator with empty index set.
| Constructor Summary | |
|---|---|
protected |
DocumentIterators.EmptyDocumentIterator()
|
| Method Summary | |
|---|---|
boolean |
accept(DocumentIteratorVisitor visitor)
Accepts a visitor. |
boolean |
acceptOnTruePaths(DocumentIteratorVisitor visitor)
Accepts a visitor after a call to DocumentIterator.nextDocument(),
limiting recursion to true paths. |
void |
dispose()
Disposes this document iterator, releasing all resources. |
int |
document()
Returns the last document returned by DocumentIterator.nextDocument(). |
boolean |
hasNext()
|
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()
An alias for DocumentIterator.intervalIterator(), that has the same limitations (i.e., it will work only if
there is just one index), and that catches IOExceptions. |
int |
nextDocument()
Returns the next document provided by this document iterator, or -1 if no more documents are available. |
int |
nextInt()
Returns the next document. |
int |
skipTo(int n)
Skips all documents smaller than n. |
| Methods inherited from class it.unimi.dsi.fastutil.ints.AbstractIntIterator |
|---|
next, remove, skip |
| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Methods inherited from interface it.unimi.dsi.fastutil.ints.IntIterator |
|---|
skip |
| Methods inherited from interface java.util.Iterator |
|---|
next, remove |
| Constructor Detail |
|---|
protected DocumentIterators.EmptyDocumentIterator()
| Method Detail |
|---|
public IntervalIterator intervalIterator()
DocumentIteratorThis is a commodity method that can be used only for queries built over a single index.
intervalIterator in interface DocumentIteratorDocumentIterator.intervalIterator(Index)public IntervalIterator intervalIterator(Index index)
DocumentIteratorAfter 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.
intervalIterator in interface DocumentIteratorindex - an index (must be one over which the query was built).
index.public Reference2ReferenceMap<Index,IntervalIterator> intervalIterators()
DocumentIteratorAfter 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).
intervalIterators in interface DocumentIteratorDocumentIterator.intervalIterator(Index)public ReferenceSet<Index> indices()
DocumentIterator
indices in interface DocumentIteratorpublic boolean hasNext()
hasNext in interface Iterator<Integer>public int nextDocument()
DocumentIteratorWarning: the specification of this method has significantly changed as of MG4J 1.2.
The special return value -1 is used to mark the end of iteration (a NoSuchElementException
would have been thrown before in that case, so ho harm should be caused by this change). The reason
for this change is providing fully lazy iteration over documents. Fully lazy iteration
does not provide an hasNext() method—you have to actually ask for the next
element and check the return value. Fully lazy iteration is much lighter on method calls (half) and
in most (if not all) MG4J classes leads to a much simpler logic. Moreover, DocumentIterator.nextDocument()
can be specified as throwing an IOException, which avoids the pernicious proliferation
of try/catch blocks in very short, low-level methods (it was having a detectable impact on performance).
nextDocument in interface DocumentIteratorpublic int nextInt()
DocumentIterator
nextInt in interface IntIteratornextInt in interface DocumentIteratornextInt in class AbstractIntIteratorDocumentIterator.nextDocument()public int document()
DocumentIteratorDocumentIterator.nextDocument().
document in interface DocumentIteratorDocumentIterator.nextDocument(), or -1 if no document has been returned yet.public int skipTo(int n)
DocumentIteratorn.
Define the current document k associated with this document iterator
as follows:
DocumentIterator.nextDocument() and this method have never been called;
Integer.MAX_VALUE, if a call to this method returned Integer.MAX_VALUE;
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 && k != -1 ); return k == -1 ? Integer.MAX_VALUE : k;
Thus, when a result k ≠ Integer.MAX_VALUE
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().
skipTo in interface DocumentIteratorn - a document pointer.
n if available, Integer.MAX_VALUE
otherwise.public boolean accept(DocumentIteratorVisitor visitor)
DocumentIteratorA document iterator is usually structured as composite,
with operators as internal nodes and IndexIterators
as leaves. This method implements the visitor pattern.
accept in interface DocumentIteratorvisitor - the visitor.
public boolean acceptOnTruePaths(DocumentIteratorVisitor visitor)
DocumentIteratorDocumentIterator.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.
acceptOnTruePaths in interface DocumentIteratorvisitor - the visitor.
DocumentIterator.accept(DocumentIteratorVisitor),
CounterCollectionVisitorpublic void dispose()
DocumentIteratorThis 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.
dispose in interface DocumentIteratorpublic IntervalIterator iterator()
DocumentIteratorDocumentIterator.intervalIterator(), that has the same limitations (i.e., it will work only if
there is just one index), and that catches IOExceptions.
iterator in interface DocumentIteratoriterator in interface Iterable<Interval>
|
|||||||||
| PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||
| SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD | ||||||||