org.terrier.matching
Class CollectionResultSet

java.lang.Object
  org.terrier.matching.CollectionResultSet

All Implemented Interfaces:

java.io.Serializable, ResultSet

Direct Known Subclasses:

QueryResultSet

public class CollectionResultSet
extends java.lang.Object
implements ResultSet, java.io.Serializable

This class implements the interface ResultSet and models the set of all documents in the collection. It encapsulates two arrays, one for the docids and one for the scores. It has also the occurrences matrix which counts how many query terms appear in each of the retrieved documents. The metadata related methods are empty.
This class is only used internally by the Matching class and the classes that extent it, because the arrays for the docids and scores contain one entry for each document in the collection. Therefore, the instantiation of an object of this class can be expensive. Access to the retrieved documents is enabled by using the method GetResultSet that returns a cropped result set.

Author:

Vassilis plachouras

See Also:

Serialized Form

Field Summary

protected boolean	arraysInitialised A static boolean flag indicating whether the arrays of docids and scores have been initialized (memory allocated for them) or not.
protected int[]	docids The array that stores the document ids.
protected int	exactResultSize The number of retrieved documents.
protected java.util.concurrent.locks.Lock	lock A lock for enabling access of the result set by different threads
protected short[]	occurrences The occurrences of the query terms in a document.
protected int	resultSize The number of documents that have been ranked and sorted according to their scores.
protected double[]	scores An array holding the scores of documents in the collection.
protected int	statusCode A status code for the result set.

Constructor Summary

CollectionResultSet(int numberOfDocuments)
A default constructor for the result set with a given number of documents.

CollectionResultSet(int[] _docids, double[] _scores, short[] _occurrences)
Construct a resultset from the following components

CollectionResultSet(ResultSet resultSet)
A default constructor for the result set with a given instance of the result set.

Method Summary

void	addMetaItem(java.lang.String name, int docid, java.lang.String value) Empty method.
void	addMetaItems(java.lang.String name, java.lang.String[] values) Empty method.
int[]	getDocids() Returns the documents ids after retrieval
int	getExactResultSize() Returns the exact size of the result set.
java.util.concurrent.locks.Lock	getLock() Returns the lock for enabling the modification of the result set by more than one threads.
java.lang.String	getMetaItem(java.lang.String name, int docid) Empty method.
java.lang.String[]	getMetaItems(java.lang.String name) Empty method.
java.lang.String[]	getMetaKeys() Returns the names of the meta keys which this resultset has
short[]	getOccurrences() Returns the occurrences array.
ResultSet	getResultSet(int[] positions) Extracts a subset of the resultset given by the list parameter, which contains a list of positions in the resultset that should be saved.
ResultSet	getResultSet(int start, int length) Crops the existing result file and extracts a subset from the given starting point to the ending point.
int	getResultSize() Returns the effective size of the result set.
double[]	getScores() Returns the documents scores after retrieval
int	getStatusCode() Returns the status code for the current result set.
boolean	hasMetaItems(java.lang.String name) Returns true if the resultset already has a set of metaitems with the specified name.
void	initialise() Initialises the arrays prior of retrieval.
void	initialise(double[] scs) Initialises the result set with the given scores.
void	setExactResultSize(int newExactResultSize) Sets the exact size of the result set, that is the number of documents that would be retrieved, if the result set was not truncated.
void	setResultSize(int newResultSize) Sets the effective size of the result set, that is the number of documents to be sorted after retrieval.
void	setStatusCode(int _statusCode) Sets the status code for the current result set.

Methods inherited from class java.lang.Object

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

Field Detail

docids

protected int[] docids

The array that stores the document ids.

scores

protected double[] scores

An array holding the scores of documents in the collection.

occurrences

protected short[] occurrences

The occurrences of the query terms in a document. This allows to use Boolean operators and filter documents. If the i-th query term appears in the j-th document, then the i-th bit of occurrences[j] is set, otherwise it is zero. Using a 2-byte long integer allows to check for the occurence of up to 16 query terms.

arraysInitialised

protected boolean arraysInitialised

A static boolean flag indicating whether the arrays of docids and scores have been initialized (memory allocated for them) or not.

resultSize

protected int resultSize

The number of documents that have been ranked and sorted according to their scores.

exactResultSize

protected int exactResultSize

The number of retrieved documents. This may be higher that <tt>resultSize<tt>, and corresponds to the number of documents that contain at least one query term.

lock

protected java.util.concurrent.locks.Lock lock

A lock for enabling access of the result set by different threads

statusCode

protected int statusCode

A status code for the result set.

Constructor Detail

CollectionResultSet

public CollectionResultSet(int[] _docids,
                           double[] _scores,
                           short[] _occurrences)

Construct a resultset from the following components

CollectionResultSet

public CollectionResultSet(int numberOfDocuments)

A default constructor for the result set with a given number of documents.

Parameters:

numberOfDocuments - the number of documents contained in the result set.

CollectionResultSet

public CollectionResultSet(ResultSet resultSet)

A default constructor for the result set with a given instance of the result set. The constructor creates a clone of the given result set.

Parameters:

resultSet - The given result set.

Method Detail

getLock

public java.util.concurrent.locks.Lock getLock()

Returns the lock for enabling the modification of the result set by more than one threads.

Specified by:

getLock in interface ResultSet

Returns:

the lock.

getStatusCode

public int getStatusCode()

Returns the status code for the current result set.

Specified by:

getStatusCode in interface ResultSet

Returns:

a integer status code. 0 stands success. 1 stands for empty result set. 2 stands for wrong setting of start/end parameters. 3 stands for query timeout. The values assigned to the status codes are increasing accordingly to the severity of the status.

setStatusCode

public void setStatusCode(int _statusCode)

Sets the status code for the current result set.

Specified by:

setStatusCode in interface ResultSet

getDocids

public int[] getDocids()

Returns the documents ids after retrieval

Specified by:

getDocids in interface ResultSet

getResultSize

public int getResultSize()

Returns the effective size of the result set.

Specified by:

getResultSize in interface ResultSet

Returns:

int the effective size of the result set

getOccurrences

public short[] getOccurrences()

Returns the occurrences array.

Specified by:

getOccurrences in interface ResultSet

Returns:

int[] the array the occurrences array.

getExactResultSize

public int getExactResultSize()

Returns the exact size of the result set.

Specified by:

getExactResultSize in interface ResultSet

Returns:

int the exact size of the result set

getScores

public double[] getScores()

Returns the documents scores after retrieval

Specified by:

getScores in interface ResultSet

initialise

public void initialise()

Initialises the arrays prior of retrieval.

Specified by:

initialise in interface ResultSet

initialise

public void initialise(double[] scs)

Initialises the result set with the given scores. If the length of the given array is different than the length of the internal arrays, then we re-allocate memory and create the arrays.

Specified by:

initialise in interface ResultSet

Parameters:

scs - double[] the scores to initiliase the result set with.

setResultSize

public void setResultSize(int newResultSize)

Sets the effective size of the result set, that is the number of documents to be sorted after retrieval.

Specified by:

setResultSize in interface ResultSet

Parameters:

newResultSize - int the effective size of the result set.

setExactResultSize

public void setExactResultSize(int newExactResultSize)

Sets the exact size of the result set, that is the number of documents that would be retrieved, if the result set was not truncated.

Specified by:

setExactResultSize in interface ResultSet

Parameters:

newExactResultSize - int the effective size of the result set.

addMetaItem

public void addMetaItem(java.lang.String name,
                        int docid,
                        java.lang.String value)

Empty method.

Specified by:

addMetaItem in interface ResultSet

Parameters:

name - the name of the metadata type. For example, it can be the url for adding the URLs of documents.

docid - the document identifier of the document.

value - the metadata value.

addMetaItems

public void addMetaItems(java.lang.String name,
                         java.lang.String[] values)

Empty method.

Specified by:

addMetaItems in interface ResultSet

Parameters:

name - the name of the metadata type. For example, it can be the url for adding the URLs of documents.

values - the metadata values.

getMetaItem

public java.lang.String getMetaItem(java.lang.String name,
                                    int docid)

Empty method.

Specified by:

getMetaItem in interface ResultSet

Parameters:

name - the name of the metadata type.

docid - the document identifier of the document.

Returns:

a string with the metadata information, or null of the metadata is not available.

getMetaItems

public java.lang.String[] getMetaItems(java.lang.String name)

Empty method.

Specified by:

getMetaItems in interface ResultSet

Parameters:

name - the name of the metadata type.

Returns:

an array of strings with the metadata information, or null of the metadata is not available.

getResultSet

public ResultSet getResultSet(int start,
                              int length)

Crops the existing result file and extracts a subset from the given starting point to the ending point.

Specified by:

getResultSet in interface ResultSet

Parameters:

start - the beginning of the subset.

length - the end of the subset.

Returns:

ResultSet a subset of the current result set.

getResultSet

public ResultSet getResultSet(int[] positions)

Extracts a subset of the resultset given by the list parameter, which contains a list of positions in the resultset that should be saved.
NB:The metadata hashtable is NOT reduced.

Specified by:

getResultSet in interface ResultSet

Parameters:

positions - int[] the list of elements in the current list that should be kept.

Returns:

a subset of the current result set specified by the list.

hasMetaItems

public boolean hasMetaItems(java.lang.String name)

Returns true if the resultset already has a set of metaitems with the specified name.

Specified by:

hasMetaItems in interface ResultSet

Parameters:

name - of the desired metaitem set

Returns:

true if the set exists.

getMetaKeys

public java.lang.String[] getMetaKeys()

Returns the names of the meta keys which this resultset has

Specified by:

getMetaKeys in interface ResultSet