java.lang.Object
- it.unimi.di.big.mg4j.index.Index.EmptyIndexIterator

All Implemented Interfaces:

IndexIterator, DocumentIterator, Serializable

Enclosing class:

Index
```
public class Index.EmptyIndexIterator
extends Object
implements IndexIterator, Serializable
```
An iterator returning no documents based on this index.
Note that accept(DocumentIteratorVisitor) does nothing and returns true, whereas acceptOnTruePaths(DocumentIteratorVisitor) throws an IllegalStateException, weight() returns 1 and weight(double) is a no-op.

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type Field Description

int id

String term

long termNumber

double weight
- Fields inherited from interface it.unimi.di.big.mg4j.search.DocumentIterator
  END_OF_LIST
- Fields inherited from interface it.unimi.di.big.mg4j.index.IndexIterator
  END_OF_POSITIONS

Constructor Summary

Constructors
Constructor Description

EmptyIndexIterator()

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.
`int`	`count()`	Returns the count, that is, the number of occurrences of the term in the current document.
`void`	`dispose()`	Disposes this document iterator, releasing all resources.
`long`	`document()`	Returns the last document returned by `DocumentIterator.nextDocument()`.
`long`	`frequency()`	Returns the frequency, that is, the number of documents that will be returned by this iterator.
`int`	`id()`	Returns the id of this index iterator.
`IndexIterator`	`id(int id)`	Sets the id of this index iterator.
`Index`	`index()`	Returns the index over which this iterator is built.
`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.
`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.
`int`	`nextPosition()`	Returns the next position at which the term appears in the current document.
`Payload`	`payload()`	Returns the payload, if any, associated with the current document.
`long`	`skipTo(long n)`	Skips all documents smaller than `n`.
`String`	`term()`	Returns the term whose inverted list is returned by this index iterator.
`Index.EmptyIndexIterator`	`term(CharSequence term)`	Sets the term whose inverted list is returned by this index iterator.
`long`	`termNumber()`	Returns the number of the term whose inverted list is returned by this index iterator.
`IndexIterator`	`termNumber(long term)`
`double`	`weight()`	Returns the weight associated with this iterator.
`IndexIterator`	`weight(double weight)`	Returns the weight of this index iterator.

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

- Field Detail
  - term
```
public String term
```
  - weight
```
public double weight
```
  - id
```
public int id
```
  - termNumber
```
public long termNumber
```
- Constructor Detail
  - EmptyIndexIterator
```
public EmptyIndexIterator()
```
- 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()
```
    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.
    
    See Also:
    
    DocumentIterator.intervalIterator(Index)
  - intervalIterators
```
public Reference2ReferenceMap<Index,IntervalIterator> intervalIterators()
```
    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.
    
    See Also:
    
    DocumentIterator.intervalIterator(Index)
  - intervalIterator
```
public IntervalIterator intervalIterator(Index index)
```
    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.
  - nextDocument
```
public long nextDocument()
```
    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.
  - 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)
```
    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.
  - frequency
```
public long frequency()
```
    Description copied from interface: IndexIterator
    
    Returns the frequency, that is, the number of documents that will be returned by this iterator.
    
    Specified by:
    
    frequency in interface IndexIterator
    
    Returns:
    
    the number of documents that will be returned by this iterator.
  - payload
```
public Payload payload()
```
    Description copied from interface: IndexIterator
    
    Returns the payload, if any, associated with the current document.
    
    Specified by:
    
    payload in interface IndexIterator
    
    Returns:
    
    the payload associated with the current document.
  - count
```
public int count()
```
    Description copied from interface: IndexIterator
    
    Returns the count, that is, the number of occurrences of the term in the current document.
    
    Specified by:
    
    count in interface IndexIterator
    
    Returns:
    
    the count (number of occurrences) of the term in the current document.
  - dispose
```
public void dispose()
```
    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
  - index
```
public Index index()
```
    Description copied from interface: IndexIterator
    
    Returns the index over which this iterator is built.
    
    Specified by:
    
    index in interface IndexIterator
    
    Returns:
    
    the index over which this iterator is built.
  - 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)
```
    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.
    
    See Also:
    
    DocumentIterator.accept(DocumentIteratorVisitor), CounterCollectionVisitor
  - term
```
public String term()
```
    Description copied from interface: IndexIterator
    
    Returns the term whose inverted list is returned by this index iterator.
    Usually, the term is automatically set by IndexReader.documents(CharSequence) or IndexReader.documents(long), but you can supply your own term with IndexIterator.term(CharSequence).
    
    Specified by:
    
    term in interface IndexIterator
    
    Returns:
    
    the term over which this iterator is built, as a compact mutable string.
    
    See Also:
    
    IndexIterator.termNumber()
  - term
```
public Index.EmptyIndexIterator term(CharSequence term)
```
    Description copied from interface: IndexIterator
    
    Sets the term whose inverted list is returned by this index iterator.
    Usually, the term is automatically set by Index.documents(CharSequence) or by IndexReader.documents(CharSequence), but you can use this method to ensure that IndexIterator.term() doesn't throw an exception.
    
    Specified by:
    
    term in interface IndexIterator
    
    Parameters:
    
    term - a character sequence (that will be defensively copied) that will be assumed to be the term whose inverted list is returned by this index iterator.
    
    Returns:
    
    this index iterator.
  - id
```
public int id()
```
    Description copied from interface: IndexIterator
    
    Returns the id of this index iterator.
    
    Specified by:
    
    id in interface IndexIterator
    
    Returns:
    
    the id of this index iterator.
    
    See Also:
    
    IndexIterator.id(int)
  - id
```
public IndexIterator id(int id)
```
    Description copied from interface: IndexIterator
    
    Sets the id of this index iterator.
    The id is an integer associated with each index iterator. It has no specific semantics, and can be used differently in different contexts. A typical usage pattern, for instance, is using it to assign a unique number to the index iterators contained in a composite document iterator (say, numbering consecutively the leaves of the composite).
    
    Specified by:
    
    id in interface IndexIterator
    
    Parameters:
    
    id - the new id for this index iterator.
    
    Returns:
    
    this index iterator.
  - termNumber
```
public long termNumber()
```
    Description copied from interface: IndexIterator
    
    Returns the number of the term whose inverted list is returned by this index iterator.
    Usually, the term number is automatically set by IndexReader.documents(CharSequence) or IndexReader.documents(long).
    
    Specified by:
    
    termNumber in interface IndexIterator
    
    Returns:
    
    the number of the term over which this iterator is built.
    
    See Also:
    
    IndexIterator.term()
  - termNumber
```
public IndexIterator termNumber(long term)
```
  - 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 IndexIterator weight(double weight)
```
    Description copied from interface: IndexIterator
    
    Returns the weight of this index iterator.
    
    Specified by:
    
    weight in interface DocumentIterator
    
    Specified by:
    
    weight in interface IndexIterator
    
    Parameters:
    
    weight - the weight of this index iterator.
    
    Returns:
    
    this document iterator.
    
    See Also:
    
    DocumentIterator.weight(double)
  - nextPosition
```
public int nextPosition()
                 throws IOException
```
    Description copied from interface: IndexIterator
    
    Returns the next position at which the term appears in the current document.
    
    Specified by:
    
    nextPosition in interface IndexIterator
    
    Returns:
    
    the next position of the current document in which the current term appears, or IndexIterator.END_OF_POSITIONS if there are no more positions.
    
    Throws:
    
    IOException

Class Index.EmptyIndexIterator

Field Summary

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

Fields inherited from interface it.unimi.di.big.mg4j.index.IndexIterator

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

term

weight

id

termNumber

Constructor Detail

EmptyIndexIterator

Method Detail

document

indices

intervalIterator

intervalIterators

intervalIterator

nextDocument

mayHaveNext

skipTo

frequency

payload

count

dispose

index

accept

acceptOnTruePaths

term

term

id

id

termNumber

termNumber

weight

weight

nextPosition