Package it.unimi.di.big.mg4j.index

Class BitStreamHPIndexReader.BitStreamHPIndexReaderIndexIterator

java.lang.Object

it.unimi.di.big.mg4j.index.AbstractIndexIterator

it.unimi.di.big.mg4j.index.BitStreamHPIndexReader.BitStreamHPIndexReaderIndexIterator

All Implemented Interfaces:

IndexIterator, DocumentIterator

Enclosing class:

BitStreamHPIndexReader

protected static final class BitStreamHPIndexReader.BitStreamHPIndexReaderIndexIterator
extends AbstractIndexIterator
implements IndexIterator

Field Summary

Fields

Modifier and Type	Field	Description
protected int	b	The parameter b for Golomb coding of pointers.
protected int	count	The current count (if this index contains counts).
protected CompressionFlags.Coding	countCoding	The cached copy of index.countCoding.
protected long	currentDocument	The last document pointer we read from current list, -1 if we just read the frequency, DocumentIterator.END_OF_LIST if we are beyond the end of list.
protected int	currentPosition	The index of the next position to be returned by nextPosition().
protected long	currentTerm	The current term.
protected long	frequency	The current frequency.
protected boolean	hasPointers	Whether the current terms has pointers at all (this happens when the frequency is smaller than the number of documents).
int	height	The parameter h (the maximum height of a skip tower).
protected InputBitStream	ibs	The underlying input bit stream.
protected BitStreamHPIndex	index	The reference index.
protected long	lastPositionsOffset	The offset of the positions of the current term.
protected int	log2b	The parameter log2b for Golomb coding of pointers; it is the most significant bit of b.
protected long	numberOfDocumentRecord	The number of the document record we are going to read inside the current inverted list.
protected CompressionFlags.Coding	pointerCoding	The cached copy of index.pointerCoding.
protected int[]	positionCache	The cached position array.
protected CompressionFlags.Coding	positionCoding	The cached copy of index.positionCoding.
protected InputBitStream	positions	The underlying positions input bit stream.
protected boolean	positionsUnread	Whether the positions for the current document pointer have not been fetched yet.
long	quantum	The quantum.
protected int	state	This variable tracks the current state of the reader.

Fields inherited from class it.unimi.di.big.mg4j.index.AbstractIndexIterator

id, term, 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
BitStreamHPIndexReaderIndexIterator(BitStreamHPIndexReader parent, InputBitStream ibs, InputBitStream positions)

Method Summary

Modifier and Type	Method	Description
protected IndexIterator	advance()
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.
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.
protected void	position(long term)	Positions the index on the inverted list of a given term.
long	skipTo(long p)	Skips all documents smaller than n.
long	termNumber()	Returns the number of the term whose inverted list is returned by this index iterator.
String	toString()
protected void	updatePositionCache()

Methods inherited from class it.unimi.di.big.mg4j.index.AbstractIndexIterator

accept, acceptOnTruePaths, id, id, term, term, weight, weight

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

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

accept, acceptOnTruePaths, weight

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

id, id, term, term, weight

Field Detail

index

protected final BitStreamHPIndex index

The reference index.

ibs

protected final InputBitStream ibs

The underlying input bit stream.

positions

protected final InputBitStream positions

The underlying positions input bit stream.

pointerCoding

protected final CompressionFlags.Coding pointerCoding

The cached copy of index.pointerCoding.

countCoding

protected final CompressionFlags.Coding countCoding

The cached copy of index.countCoding.

positionCoding

protected final CompressionFlags.Coding positionCoding

The cached copy of index.positionCoding.

b

protected int b

The parameter b for Golomb coding of pointers.

log2b

protected int log2b

The parameter log2b for Golomb coding of pointers; it is the most significant bit of b.

currentTerm

protected long currentTerm

The current term.

frequency

protected long frequency

The current frequency.

hasPointers

protected boolean hasPointers

Whether the current terms has pointers at all (this happens when the frequency is smaller than the number of documents).

count

protected int count

The current count (if this index contains counts).

currentDocument

protected long currentDocument

The last document pointer we read from current list, -1 if we just read the frequency, DocumentIterator.END_OF_LIST if we are beyond the end of list.

numberOfDocumentRecord

protected long numberOfDocumentRecord

The number of the document record we are going to read inside the current inverted list.

state

protected int state

This variable tracks the current state of the reader.

height

public final int height

The parameter h (the maximum height of a skip tower).

quantum

public long quantum

The quantum.

positionsUnread

protected boolean positionsUnread

Whether the positions for the current document pointer have not been fetched yet.

positionCache

protected int[] positionCache

The cached position array.

currentPosition

protected int currentPosition

The index of the next position to be returned by nextPosition().

lastPositionsOffset

protected long lastPositionsOffset

The offset of the positions of the current term.

Constructor Detail

BitStreamHPIndexReaderIndexIterator

public BitStreamHPIndexReaderIndexIterator(BitStreamHPIndexReader parent,
                                           InputBitStream ibs,
                                           InputBitStream positions)

Method Detail

position

protected void position(long term)
                 throws IOException

Positions the index on the inverted list of a given term.

This method can be called at any time. Note that it is always possible to call this method with argument 0, even if offsets have not been loaded.

Parameters:

term - a term.

Throws:

IOException

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()

advance

protected IndexIterator advance()
                         throws IOException

Throws:

IOException

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.

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.

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.

payload

public Payload payload()
                throws IOException

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.

Throws:

IOException

count

public int count()
          throws IOException

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.

Throws:

IOException

updatePositionCache

protected void updatePositionCache()
                            throws IOException

Throws:

IOException

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

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

skipTo

public long skipTo(long p)
            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:

p - 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

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.

toString

public String toString()

Overrides:

toString in class Object

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)

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)

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

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.