PostingListManager (Terrier Information Retrieval Platform 5.1 API)

java.lang.Object
- org.terrier.matching.PostingListManager

All Implemented Interfaces:

Closeable, AutoCloseable
```
public class PostingListManager
extends Object
implements Closeable
```
The PostingListManager is responsible for opening the appropriate posting lists IterablePosting given the MatchingQueryTerms object. Moreover, it knows how each Posting should be scored.
Plugins are also supported by PostingListManager. Each plugin class should implement the PostingListManagerPlugin interface, and be named explicitly in the matching.postinglist.manager.plugins property.
Properties:
- ignore.low.idf.terms - should terms with low IDF (i.e. very frequent) be ignored? Defaults to false, i.e. ignored
- matching.postinglist.manager.plugins - Comma delimited list of PostingListManagerPlugin classes to load.
Example Usage
Following code shows how term-at-a-time matching may occur using the PostingListManager:
```
 
 MatchingQueryTerms mqt;
 Index index;
 PostingListManager plm = new PostingListManager(index, index.getCollectionStatistics(), mqt);
 plm.prepare(false);
 for(int term = 0;term > plm.size(); term++)
 {
   IterablePosting ip = plm.get(term);
   while(ip.next() != IterablePosting.EOL)
   {
     double score = plm.score(term);
     int id = ip.getId();
   }
 }
 plm.close();
 
```
Since:

3.5

Author:

Nicola Tonellotto and Craig Macdonald

See Also:

Matching

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static interface`	`PostingListManager.PostingListManagerPlugin` Interface for plugins to further alter the posting lists managed by the PostingListManager

Field Summary

Fields
Modifier and Type	Field and Description
`protected CollectionStatistics`	`collectionStatistics` statistics of the collection
`protected static boolean`	`IGNORE_LOW_IDF_TERMS` A property that enables to ignore the terms with a low IDF.
`protected Index`	`index` underlying index
`protected PostingIndex<Pointer>`	`invertedIndex` inverted index of the index
`protected Lexicon<String>`	`lexicon` lexicon for the index
`protected static org.slf4j.Logger`	`logger`
`protected gnu.trove.TIntArrayList`	`matchOnTerms`
`protected long`	`negRequiredBitMask`
`protected gnu.trove.TIntArrayList`	`nonMatchOnTerms`
`protected int`	`numTerms` number of terms
`protected static PostingListManager.PostingListManagerPlugin[]`	`plugins`
`protected long`	`requiredBitMask` which terms are positively required to match in retrieved documents
`protected gnu.trove.TDoubleArrayList`	`termKeyFreqs` key (query) frequencies for each term
`protected List<WeightingModel>`	`termModels` weighting models for each term
`protected List<IterablePosting>`	`termPostings` posting lists for each term
`protected List<EntryStatistics>`	`termStatistics` EntryStatistics for each term
`protected List<String>`	`termStrings` String form for each term
`protected List<Set<String>>`	`termTags` String form for each term

Constructor Summary

Constructors
Modifier	Constructor and Description
`protected`	`PostingListManager(Index _index, CollectionStatistics cs)` Create a posting list manager for the given index and statistics
	`PostingListManager(Index _index, CollectionStatistics _cs, MatchingQueryTerms mqt)` Create a posting list manager for the given index and statistics, and populated using the specified MatchingQueryTerms.
	`PostingListManager(Index _index, CollectionStatistics _cs, MatchingQueryTerms mqt, boolean splitSynonyms, String scoringTag, String additionalTag)` Create a posting list manager for the given index and statistics, and populated using the specified MatchingQueryTerms.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`close()`
`double`	`getKeyFrequency(int i)`
`int[]`	`getMatchingTerms()` Returns the indices of the terms that are considered (i.e.
`long`	`getNegRequiredBitMask()`
`int[]`	`getNonMatchingTerms()` Returns the indices of the terms that must be called through assignScore() but not actually used to match documents.
`int`	`getNumTerms()` Returns the number of postings lists (that are terms) for this query
`IterablePosting`	`getPosting(int i)` Returns the IterablePosting corresponding to the specified term
`long`	`getRequiredBitMask()`
`EntryStatistics`	`getStatistics(int i)` Returns the EntryStatistics corresponding to the specified term
`Set<String>`	`getTags(int i)`
`String`	`getTerm(int i)`
`static EntryStatistics`	`mergeStatistics(EntryStatistics[] entryStats)` Knows how to merge several EntryStatistics for a single effective term
`void`	`prepare(boolean firstMove)` Counts the number of terms active.
`double`	`score(int i)` Returns the score using all weighting models for the current posting of the specified term
`int`	`size()` Returns the number of posting lists for this query

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

- Field Detail
  - logger
```
protected static final org.slf4j.Logger logger
```
  - IGNORE_LOW_IDF_TERMS
```
protected static boolean IGNORE_LOW_IDF_TERMS
```
    A property that enables to ignore the terms with a low IDF. Controlled by ignore.low.idf.terms property, defualts to false.
  - plugins
```
protected static PostingListManager.PostingListManagerPlugin[] plugins
```
  - termPostings
```
protected final List<IterablePosting> termPostings
```
    posting lists for each term
  - termModels
```
protected final List<WeightingModel> termModels
```
    weighting models for each term
  - termStatistics
```
protected final List<EntryStatistics> termStatistics
```
    EntryStatistics for each term
  - termStrings
```
protected final List<String> termStrings
```
    String form for each term
  - termTags
```
protected final List<Set<String>> termTags
```
    String form for each term
  - matchOnTerms
```
protected final gnu.trove.TIntArrayList matchOnTerms
```
  - nonMatchOnTerms
```
protected final gnu.trove.TIntArrayList nonMatchOnTerms
```
  - termKeyFreqs
```
protected final gnu.trove.TDoubleArrayList termKeyFreqs
```
    key (query) frequencies for each term
  - numTerms
```
protected int numTerms
```
    number of terms
  - index
```
protected Index index
```
    underlying index
  - lexicon
```
protected Lexicon<String> lexicon
```
    lexicon for the index
  - invertedIndex
```
protected PostingIndex<Pointer> invertedIndex
```
    inverted index of the index
  - collectionStatistics
```
protected CollectionStatistics collectionStatistics
```
    statistics of the collection
  - requiredBitMask
```
protected long requiredBitMask
```
    which terms are positively required to match in retrieved documents
  - negRequiredBitMask
```
protected long negRequiredBitMask
```
- Constructor Detail
  - PostingListManager
```
protected PostingListManager(Index _index,
                             CollectionStatistics cs)
                      throws IOException
```
    Create a posting list manager for the given index and statistics
    
    Throws:
    
    IOException
  - PostingListManager
```
public PostingListManager(Index _index,
                          CollectionStatistics _cs,
                          MatchingQueryTerms mqt)
                   throws IOException
```
    Create a posting list manager for the given index and statistics, and populated using the specified MatchingQueryTerms.
    
    Parameters:
    
    _index - - index to obtain postings from
    
    _cs - - collection statistics to obtain
    
    mqt - - MatchingQueryTerms object calculated for the query
    
    Throws:
    
    IOException
  - PostingListManager
```
public PostingListManager(Index _index,
                          CollectionStatistics _cs,
                          MatchingQueryTerms mqt,
                          boolean splitSynonyms,
                          String scoringTag,
                          String additionalTag)
                   throws IOException
```
    Create a posting list manager for the given index and statistics, and populated using the specified MatchingQueryTerms.
    
    Parameters:
    
    _index - - index to obtain postings from
    
    _cs - - collection statistics to obtain
    
    mqt - - MatchingQueryTerms object calculated for the query
    
    splitSynonyms - - allows the splitting of synonym groups (i.e. singleTermAlternatives) to be disabled
    
    Throws:
    
    IOException
- Method Detail
  - mergeStatistics
```
public static EntryStatistics mergeStatistics(EntryStatistics[] entryStats)
```
    Knows how to merge several EntryStatistics for a single effective term
  - prepare
```
public void prepare(boolean firstMove)
             throws IOException
```
    Counts the number of terms active. If firstMove is true, it will move each posting to the first posting.
    
    Parameters:
    
    firstMove - move all postings to the start?
    
    Throws:
    
    IOException
  - getStatistics
```
public EntryStatistics getStatistics(int i)
```
    Returns the EntryStatistics corresponding to the specified term
    
    Parameters:
    
    i - term to obtain statistics for
    
    Returns:
    
    Statistics for this i-1th term
  - getPosting
```
public IterablePosting getPosting(int i)
```
    Returns the IterablePosting corresponding to the specified term
    
    Parameters:
    
    i - term to obtain the posting list for
    
    Returns:
    
    Posting list for this i-1th term
  - size
```
public int size()
```
    Returns the number of posting lists for this query
  - getNumTerms
```
public int getNumTerms()
```
    Returns the number of postings lists (that are terms) for this query
  - getMatchingTerms
```
public int[] getMatchingTerms()
```
    Returns the indices of the terms that are considered (i.e. scored) during matching
  - getNonMatchingTerms
```
public int[] getNonMatchingTerms()
```
    Returns the indices of the terms that must be called through assignScore() but not actually used to match documents.
  - score
```
public double score(int i)
```
    Returns the score using all weighting models for the current posting of the specified term
    
    Parameters:
    
    i - Which term to score
    
    Returns:
    
    score obtained from all weighting models for that term
  - close
```
public void close()
           throws IOException
```
    Specified by:
    
    close in interface Closeable
    
    Specified by:
    
    close in interface AutoCloseable
    
    Throws:
    
    IOException
  - getRequiredBitMask
```
public long getRequiredBitMask()
```
  - getNegRequiredBitMask
```
public long getNegRequiredBitMask()
```
  - getTerm
```
public String getTerm(int i)
```
  - getTags
```
public Set<String> getTags(int i)
```
  - getKeyFrequency
```
public double getKeyFrequency(int i)
```

Class PostingListManager

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

logger

IGNORE_LOW_IDF_TERMS

plugins

termPostings

termModels

termStatistics

termStrings

termTags

matchOnTerms

nonMatchOnTerms

termKeyFreqs

numTerms

index

lexicon

invertedIndex

collectionStatistics

requiredBitMask

negRequiredBitMask

Constructor Detail

PostingListManager

PostingListManager

PostingListManager

Method Detail

mergeStatistics

prepare

getStatistics

getPosting

size

getNumTerms

getMatchingTerms

getNonMatchingTerms

score

close

getRequiredBitMask

getNegRequiredBitMask

getTerm

getTags

getKeyFrequency