Package org.apache.lucene.index.pruning
Class TFTermPruningPolicy
- 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.TermPruningPolicy
fieldFlags, in
-
Fields inherited from class org.apache.lucene.index.pruning.PruningPolicy
DEL_ALL, DEL_PAYLOADS, DEL_POSTINGS, DEL_STORED, DEL_VECTOR
-
-
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 movingTermPositions
to a newTerm
.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 org.apache.lucene.index.pruning.TermPruningPolicy
pruneAllFieldPostings, prunePayload, pruneWholeTermVector
-
-
-
-
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 classTermPruningPolicy
- 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 movingTermPositions
to a newTerm
.- Specified by:
initPositionsTerm
in classTermPruningPolicy
- Parameters:
in
- input term positionst
- 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 classTermPruningPolicy
- Parameters:
termPositions
- positioned term positions. Implementations MUST NOT advance this by callingTermPositions
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 classTermPruningPolicy
- Parameters:
docNumber
- document numberfield
- field nameterms
- array of termsfreqs
- array of term frequenciestfv
- 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 classTermPruningPolicy
- Parameters:
docNum
- current document numberpositions
- 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.
-
-