/*
* Created on 28-Oct-2004
*/
package org.apache.lucene.search.highlight;
import java.io.IOException;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.Token;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.TermFreqVector;
import org.apache.lucene.index.TermPositionVector;
import org.apache.lucene.index.TermVectorOffsetInfo;
/**
* Hides implementation issues associated with obtaining a TokenStream for use with
* the higlighter - can obtain from TermFreqVectors with offsets and (optionally) positions or
* from Analyzer class reparsing the stored content.
* @author maharwood
*/
public class TokenSources
{
/**
* A convenience method that tries a number of approaches to getting a token stream.
* The cost of finding there are no termVectors in the index is minimal (1000 invocations still
* registers 0 ms). So this "lazy" (flexible?) approach to coding is probably acceptable
* @param reader
* @param docId
* @param field
* @param analyzer
* @return null if field not stored correctly
* @throws IOException
*/
public static TokenStream getAnyTokenStream(IndexReader reader,int docId, String field,Analyzer analyzer) throws IOException
{
TokenStream ts=null;
TermFreqVector tfv=(TermFreqVector) reader.getTermFreqVector(docId,field);
if(tfv!=null)
{
if(tfv instanceof TermPositionVector)
{
ts=getTokenStream((TermPositionVector) tfv);
}
}
//No token info stored so fall back to analyzing raw content
if(ts==null)
{
ts=getTokenStream(reader,docId,field,analyzer);
}
return ts;
}
public static TokenStream getTokenStream(TermPositionVector tpv)
{
//assumes the worst and makes no assumptions about token position sequences.
return getTokenStream(tpv,false);
}
/**
* Low level api.
* Returns a token stream or null if no offset info available in index.
* This can be used to feed the highlighter with a pre-parsed token stream
*
* In my tests the speeds to recreate 1000 token streams using this method are:
* - with TermVector offset only data stored - 420 milliseconds
* - with TermVector offset AND position data stored - 271 milliseconds
* (nb timings for TermVector with position data are based on a tokenizer with contiguous
* positions - no overlaps or gaps)
* The cost of not using TermPositionVector to store
* pre-parsed content and using an analyzer to re-parse the original content:
* - reanalyzing the original content - 980 milliseconds
*
* The re-analyze timings will typically vary depending on -
* 1) The complexity of the analyzer code (timings above were using a
* stemmer/lowercaser/stopword combo)
* 2) The number of other fields (Lucene reads ALL fields off the disk
* when accessing just one document field - can cost dear!)
* 3) Use of compression on field storage - could be faster cos of compression (less disk IO)
* or slower (more CPU burn) depending on the content.
*
* @param tpv
* @param tokenPositionsGuaranteedContiguous true if the token position numbers have no overlaps or gaps. If looking
* to eek out the last drops of performance, set to true. If in doubt, set to false.
*/
public static TokenStream getTokenStream(TermPositionVector tpv, boolean tokenPositionsGuaranteedContiguous)
{
//an object used to iterate across an array of tokens
class StoredTokenStream extends TokenStream
{
Token tokens[];
int currentToken=0;
StoredTokenStream(Token tokens[])
{
this.tokens=tokens;
}
public Token next()
{
if(currentToken>=tokens.length)
{
return null;
}
return tokens[currentToken++];
}
}
//code to reconstruct the original sequence of Tokens
String[] terms=tpv.getTerms();
int[] freq=tpv.getTermFrequencies();
int totalTokens=0;
for (int t = 0; t < freq.length; t++)
{
totalTokens+=freq[t];
}
Token tokensInOriginalOrder[]=new Token[totalTokens];
ArrayList unsortedTokens = null;
for (int t = 0; t < freq.length; t++)
{
TermVectorOffsetInfo[] offsets=tpv.getOffsets(t);
if(offsets==null)
{
return null;
}
int[] pos=null;
if(tokenPositionsGuaranteedContiguous)
{
//try get the token position info to speed up assembly of tokens into sorted sequence
pos=tpv.getTermPositions(t);
}
if(pos==null)
{
//tokens NOT stored with positions or not guaranteed contiguous - must add to list and sort later
if(unsortedTokens==null)
{
unsortedTokens=new ArrayList();
}
for (int tp = 0; tp < offsets.length; tp++)
{
unsortedTokens.add(new Token(terms[t],
offsets[tp].getStartOffset(),
offsets[tp].getEndOffset()));
}
}
else
{
//We have positions stored and a guarantee that the token position information is contiguous
// This may be fast BUT wont work if Tokenizers used which create >1 token in same position or
// creates jumps in position numbers - this code would fail under those circumstances
//tokens stored with positions - can use this to index straight into sorted array
for (int tp = 0; tp < pos.length; tp++)
{
tokensInOriginalOrder[pos[tp]]=new Token(terms[t],
offsets[tp].getStartOffset(),
offsets[tp].getEndOffset());
}
}
}
//If the field has been stored without position data we must perform a sort
if(unsortedTokens!=null)
{
tokensInOriginalOrder=(Token[]) unsortedTokens.toArray(new Token[unsortedTokens.size()]);
Arrays.sort(tokensInOriginalOrder, new Comparator(){
public int compare(Object o1, Object o2)
{
Token t1=(Token) o1;
Token t2=(Token) o2;
if(t1.startOffset()>t2.startOffset())
return 1;
if(t1.startOffset()<t2.startOffset())
return -1;
return 0;
}});
}
return new StoredTokenStream(tokensInOriginalOrder);
}
public static TokenStream getTokenStream(IndexReader reader,int docId, String field) throws IOException
{
TermFreqVector tfv=(TermFreqVector) reader.getTermFreqVector(docId,field);
if(tfv==null)
{
throw new IllegalArgumentException(field+" in doc #"+docId
+"does not have any term position data stored");
}
if(tfv instanceof TermPositionVector)
{
TermPositionVector tpv=(TermPositionVector) reader.getTermFreqVector(docId,field);
return getTokenStream(tpv);
}
throw new IllegalArgumentException(field+" in doc #"+docId
+"does not have any term position data stored");
}
//convenience method
public static TokenStream getTokenStream(IndexReader reader,int docId, String field,Analyzer analyzer) throws IOException
{
Document doc=reader.document(docId);
String contents=doc.get(field);
if(contents==null)
{
throw new IllegalArgumentException("Field "+field +" in document #"+docId+ " is not stored and cannot be analyzed");
}
return analyzer.tokenStream(field,new StringReader(contents));
}
}