TFTermPruningPolicy (Lucene 3.6.2 API)

java.lang.Object
- org.apache.lucene.index.pruning.PruningPolicy
- - org.apache.lucene.index.pruning.TermPruningPolicy
  - - org.apache.lucene.index.pruning.TFTermPruningPolicy

```
public class TFTermPruningPolicy
extends TermPruningPolicy
```
Policy for producing smaller index out of an input index, by removing postings data for those terms where their in-document frequency is below a specified threshold.
Larger threshold value will produce a smaller index. See TermPruningPolicy for size vs performance considerations.
This implementation uses simple term frequency thresholds to remove all postings from documents where a given term occurs rarely (i.e. its TF in a document is smaller than the threshold).
Threshold values in this method are expressed as absolute term frequencies.

Field Summary

Fields
Modifier and Type Field Description

protected int curThr

protected int defThreshold

protected Map<String,Integer> thresholds
- Fields inherited from class org.apache.lucene.index.pruning.PruningPolicy
  DEL_ALL, DEL_PAYLOADS, DEL_POSTINGS, DEL_STORED, DEL_VECTOR
- Fields inherited from class org.apache.lucene.index.pruning.TermPruningPolicy
  fieldFlags, in

Fields
Modifier and Type	Field	Description
`protected int`	`curThr`
`protected int`	`defThreshold`
`protected Map<String,Integer>`	`thresholds`

Constructor Summary

Constructors
Constructor	Description
`TFTermPruningPolicy(IndexReader in, Map<String,Integer> fieldFlags, Map<String,Integer> thresholds, int defThreshold)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`initPositionsTerm(TermPositions in, Term t)`	Called when moving `TermPositions` to a new `Term`.
`boolean`	`pruneAllPositions(TermPositions termPositions, Term t)`	Prune all postings per term (invoked once per term per doc)
`int`	`pruneSomePositions(int docNum, int[] positions, Term curTerm)`	Prune some postings per term (invoked once per term per doc).
`boolean`	`pruneTermEnum(TermEnum te)`	Pruning of all postings for a term (invoked once per term).
`int`	`pruneTermVectorTerms(int docNumber, String field, String[] terms, int[] freqs, TermFreqVector tfv)`	Pruning of individual terms in term vectors.

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

Methods inherited from class org.apache.lucene.index.pruning.TermPruningPolicy
pruneAllFieldPostings, prunePayload, pruneWholeTermVector

- Field Detail
  - thresholds
```
protected Map<String,Integer> thresholds
```
  - defThreshold
```
protected int defThreshold
```
  - curThr
```
protected int curThr
```
- Constructor Detail
  - TFTermPruningPolicy
```
public TFTermPruningPolicy(IndexReader in,
                           Map<String,Integer> fieldFlags,
                           Map<String,Integer> thresholds,
                           int defThreshold)
```
- Method Detail
  - pruneTermEnum
```
public boolean pruneTermEnum(TermEnum te)
                      throws IOException
```
    Description copied from class: TermPruningPolicy
    
    Pruning of all postings for a term (invoked once per term).
    
    Specified by:
    
    pruneTermEnum in class TermPruningPolicy
    
    Parameters:
    
    te - positioned term enum.
    
    Returns:
    
    true if all postings for this term should be removed, false otherwise.
    
    Throws:
    
    IOException
  - initPositionsTerm
```
public void initPositionsTerm(TermPositions in,
                              Term t)
                       throws IOException
```
    Description copied from class: TermPruningPolicy
    
    Called when moving TermPositions to a new Term.
    
    Specified by:
    
    initPositionsTerm in class TermPruningPolicy
    
    Parameters:
    
    in - input term positions
    
    t - current term
    
    Throws:
    
    IOException
  - pruneAllPositions
```
public boolean pruneAllPositions(TermPositions termPositions,
                                 Term t)
                          throws IOException
```
    Description copied from class: TermPruningPolicy
    
    Prune all postings per term (invoked once per term per doc)
    
    Specified by:
    
    pruneAllPositions in class TermPruningPolicy
    
    Parameters:
    
    termPositions - positioned term positions. Implementations MUST NOT advance this by calling TermPositions methods that advance either the position pointer (next, skipTo) or term pointer (seek).
    
    t - current term
    
    Returns:
    
    true if the current posting should be removed, false otherwise.
    
    Throws:
    
    IOException
  - pruneTermVectorTerms
```
public int pruneTermVectorTerms(int docNumber,
                                String field,
                                String[] terms,
                                int[] freqs,
                                TermFreqVector tfv)
                         throws IOException
```
    Description copied from class: TermPruningPolicy
    
    Pruning of individual terms in term vectors.
    
    Specified by:
    
    pruneTermVectorTerms in class TermPruningPolicy
    
    Parameters:
    
    docNumber - document number
    
    field - field name
    
    terms - array of terms
    
    freqs - array of term frequencies
    
    tfv - the original term frequency vector
    
    Returns:
    
    0 if no terms are to be removed, positive number to indicate how many terms need to be removed. The same number of entries in the terms array must be set to null to indicate which terms to remove.
    
    Throws:
    
    IOException
  - pruneSomePositions
```
public int pruneSomePositions(int docNum,
                              int[] positions,
                              Term curTerm)
```
    Description copied from class: TermPruningPolicy
    
    Prune some postings per term (invoked once per term per doc).
    
    Specified by:
    
    pruneSomePositions in class TermPruningPolicy
    
    Parameters:
    
    docNum - current document number
    
    positions - original term positions in the document (and indirectly term frequency)
    
    curTerm - current term
    
    Returns:
    
    0 if no postings are to be removed, or positive number to indicate how many postings need to be removed. The same number of entries in the positions array must be set to -1 to indicate which positions to remove.

Class TFTermPruningPolicy

Field Summary

Fields inherited from class org.apache.lucene.index.pruning.PruningPolicy

Fields inherited from class org.apache.lucene.index.pruning.TermPruningPolicy

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from class org.apache.lucene.index.pruning.TermPruningPolicy

Field Detail

thresholds

defThreshold

curThr

Constructor Detail

TFTermPruningPolicy

Method Detail

pruneTermEnum

initPositionsTerm

pruneAllPositions

pruneTermVectorTerms

pruneSomePositions