org.terrier.structures
Class CollectionStatistics

java.lang.Object
  org.terrier.structures.CollectionStatistics

All Implemented Interfaces:

Serializable, org.apache.hadoop.io.Writable

Direct Known Subclasses:

Index.UpdatingCollectionStatistics

public class CollectionStatistics
extends Object
implements Serializable, org.apache.hadoop.io.Writable

This class provides basic statistics for the indexed collection of documents, such as the average length of documents, or the total number of documents in the collection.
After indexing, statistics are saved in the PREFIX.log file, along with the classes that should be used for the Lexicon, the DocumentIndex, the DirectIndex and the InvertedIndex. This means that an index knows how it was build and how it should be opened again.

Author:

Gianni Amati, Vassilis Plachouras, Craig Macdonald

See Also:

Serialized Form

Field Summary

protected double	averageDocumentLength The average length of a document in the collection.
protected double[]	avgFieldLengths Average length of each field
protected long[]	fieldTokens number of tokens in each field
protected int	numberOfDocuments The total number of documents in the collection.
protected int	numberOfFields Number of fields used to index
protected long	numberOfPointers The total number of pointers in the inverted file.
protected long	numberOfTokens The total number of tokens in the collection.
protected int	numberOfUniqueTerms The total number of unique terms in the collection.

Constructor Summary

CollectionStatistics()

CollectionStatistics(int numDocs, int numTerms, long numTokens, long numPointers, long[] _fieldTokens)
Constructs an instance of the class with

Method Summary

void	addStatistics(CollectionStatistics cs) Increment the statistics by the specified amount
double	getAverageDocumentLength() Returns the documents' average length.
double[]	getAverageFieldLengths() Returns the average length of each field in tokens
long[]	getFieldTokens() Returns the length of each field in tokens
int	getNumberOfDocuments() Returns the total number of documents in the collection.
int	getNumberOfFields() Returns the number of fields being used to index
long	getNumberOfPointers() Returns the total number of pointers in the collection.
long	getNumberOfTokens() Returns the total number of tokens in the collection.
int	getNumberOfUniqueTerms() Returns the total number of unique terms in the lexicon.
void	readFields(DataInput in)
protected void	relcaluateAverageLengths()
String	toString() Returns a concrete representation of an index's statistics
void	write(DataOutput out)

Methods inherited from class java.lang.Object

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

Field Detail

numberOfFields

protected int numberOfFields

Number of fields used to index

fieldTokens

protected long[] fieldTokens

number of tokens in each field

avgFieldLengths

protected double[] avgFieldLengths

Average length of each field

numberOfDocuments

protected int numberOfDocuments

The total number of documents in the collection.

numberOfTokens

protected long numberOfTokens

The total number of tokens in the collection.

numberOfPointers

protected long numberOfPointers

The total number of pointers in the inverted file. This corresponds to the sum of the document frequencies for the terms in the lexicon.

numberOfUniqueTerms

protected int numberOfUniqueTerms

The total number of unique terms in the collection. This corresponds to the number of entries in the lexicon.

averageDocumentLength

protected double averageDocumentLength

The average length of a document in the collection.

Constructor Detail

CollectionStatistics

public CollectionStatistics(int numDocs,
                            int numTerms,
                            long numTokens,
                            long numPointers,
                            long[] _fieldTokens)

Constructs an instance of the class with

Parameters:

numDocs -

numTerms -

numTokens -

numPointers -

_fieldTokens -

CollectionStatistics

public CollectionStatistics()

Method Detail

relcaluateAverageLengths

protected void relcaluateAverageLengths()

toString

public String toString()

Returns a concrete representation of an index's statistics

Overrides:

toString in class Object

getAverageDocumentLength

public double getAverageDocumentLength()

Returns the documents' average length.

Returns:

the average length of the documents in the collection.

getNumberOfDocuments

public int getNumberOfDocuments()

Returns the total number of documents in the collection.

Returns:

the total number of documents in the collection

getNumberOfPointers

public long getNumberOfPointers()

Returns the total number of pointers in the collection.

Returns:

the total number of pointers in the collection

getNumberOfTokens

public long getNumberOfTokens()

Returns the total number of tokens in the collection.

Returns:

the total number of tokens in the collection

getNumberOfUniqueTerms

public int getNumberOfUniqueTerms()

Returns the total number of unique terms in the lexicon.

Returns:

the total number of unique terms in the lexicon

getNumberOfFields

public int getNumberOfFields()

Returns the number of fields being used to index

getFieldTokens

public long[] getFieldTokens()

Returns the length of each field in tokens

getAverageFieldLengths

public double[] getAverageFieldLengths()

Returns the average length of each field in tokens

addStatistics

public void addStatistics(CollectionStatistics cs)

Increment the statistics by the specified amount

readFields

public void readFields(DataInput in)
                throws IOException

Specified by:

readFields in interface org.apache.hadoop.io.Writable

Throws:

IOException

write

public void write(DataOutput out)
           throws IOException

Specified by:

write in interface org.apache.hadoop.io.Writable

Throws:

IOException