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java.lang.Objectit.unimi.dsi.fastutil.ints.AbstractIntIterator
it.unimi.dsi.mg4j.search.AbstractDocumentIterator
it.unimi.dsi.mg4j.search.AbstractCompositeDocumentIterator
it.unimi.dsi.mg4j.search.AbstractUnionDocumentIterator
public abstract class AbstractUnionDocumentIterator
A document iterator on documents, generating the union of the documents returned by a number of document iterators.
The pattern of this class is the same as that of AbstractIntersectionDocumentIterator
.
Additionally, this class provides a mechanism that makes accessible the set of component
document iterators that are positioned on the current document.
Nested Class Summary |
---|
Nested classes/interfaces inherited from class it.unimi.dsi.mg4j.search.AbstractCompositeDocumentIterator |
---|
AbstractCompositeDocumentIterator.AbstractCompositeIndexIntervalIterator, AbstractCompositeDocumentIterator.AbstractCompositeIntervalIterator |
Nested classes/interfaces inherited from class it.unimi.dsi.mg4j.search.AbstractDocumentIterator |
---|
AbstractDocumentIterator.AbstractIntervalIterator |
Field Summary | |
---|---|
protected int[] |
curr
The reference array used for the queue. |
protected int[] |
front
The IndirectPriorityQueue.front(int[]) of queue , if frontSize is not -1. |
protected int |
frontSize
The number of valid entries in front , or -1 if the front has not been computed for the current document. |
protected IntHeapSemiIndirectPriorityQueue |
queue
A heap-based semi-indirect priority queue used to keep track of the currently scanned integers. |
Fields inherited from class it.unimi.dsi.mg4j.search.AbstractCompositeDocumentIterator |
---|
documentIterator, indexIterator, indices, n, soleIndex |
Fields inherited from class it.unimi.dsi.mg4j.search.AbstractDocumentIterator |
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last, next, weight |
Constructor Summary | |
---|---|
protected |
AbstractUnionDocumentIterator(DocumentIterator... documentIterator)
Creates a new document iterator that computes the OR of the given array of iterators. |
Method Summary | ||
---|---|---|
|
acceptOnTruePaths(DocumentIteratorVisitor<T> visitor)
Invokes acceptOnTruePaths(DocumentIteratorVisitor) only on component
iterators positioned on the current document. |
|
protected int |
computeFront()
Forces computation of the current front, returning the number of indices it contains. |
|
protected abstract IntervalIterator |
getComposedIntervalIterator(Index index)
|
|
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 -1 if no more documents are available. |
|
int |
skipTo(int n)
Skips all documents smaller than n . |
Methods inherited from class it.unimi.dsi.mg4j.search.AbstractCompositeDocumentIterator |
---|
accept, dispose, indices, intervalIterator, toString |
Methods inherited from class it.unimi.dsi.mg4j.search.AbstractDocumentIterator |
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document, hasNext, iterator, nextInt, weight, weight |
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, wait, wait, wait |
Methods inherited from interface it.unimi.dsi.mg4j.search.DocumentIterator |
---|
document, iterator, nextInt, weight, weight |
Methods inherited from interface it.unimi.dsi.fastutil.ints.IntIterator |
---|
skip |
Methods inherited from interface java.util.Iterator |
---|
hasNext, next, remove |
Field Detail |
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protected final IntHeapSemiIndirectPriorityQueue queue
protected final int[] front
IndirectPriorityQueue.front(int[])
of queue
, if frontSize
is not -1.
protected final int[] curr
protected int frontSize
front
, or -1 if the front has not been computed for the current document.
Constructor Detail |
---|
protected AbstractUnionDocumentIterator(DocumentIterator... documentIterator) throws IOException
documentIterator
- the iterators to be joined.
IOException
Method Detail |
---|
public int skipTo(int n) throws IOException
DocumentIterator
n
.
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()
.
n
- a document pointer.
n
if available, Integer.MAX_VALUE
otherwise.
IOException
public int nextDocument() throws IOException
DocumentIterator
Warning: 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).
IOException
protected int computeFront()
After a call to this method,
the first elements of front
contain
the indices of the component document iterators
that are positioned on the current document. If the front has already been
computed for the current document, this method has no side effects.
front
).public Reference2ReferenceMap<Index,IntervalIterator> intervalIterators() throws IOException
DocumentIterator
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)
.
IOException
DocumentIterator.intervalIterator(Index)
public IntervalIterator intervalIterator(Index index) throws IOException
DocumentIterator
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.
index
- an index (must be one over which the query was built).
index
.
IOException
protected abstract IntervalIterator getComposedIntervalIterator(Index index)
public <T> T acceptOnTruePaths(DocumentIteratorVisitor<T> visitor) throws IOException
acceptOnTruePaths(DocumentIteratorVisitor)
only on component
iterators positioned on the current document.
acceptOnTruePaths
in interface DocumentIterator
acceptOnTruePaths
in class AbstractCompositeDocumentIterator
visitor
- a visitor.
IOException
DocumentIterator.accept(DocumentIteratorVisitor)
,
CounterCollectionVisitor
|
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