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Lucene example source code file (DuplicateFilter.java)

This example Lucene source code file (DuplicateFilter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

duplicatefilter, duplicatefilter, io, ioexception, ioexception, km_use_first_occurrence=1, km_use_last_occurrence,pm_full_validation, openbitset, openbitset, override, string, term, term, termdocs, termenum

The Lucene DuplicateFilter.java source code

package org.apache.lucene.search;
/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import java.io.IOException;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.index.TermEnum;
import org.apache.lucene.util.OpenBitSet;

public class DuplicateFilter extends Filter
{
	
	String fieldName;
	
	/**
	 * KeepMode determines which document id to consider as the master, all others being 
	 * identified as duplicates. Selecting the "first occurrence" can potentially save on IO.
	 */
	int keepMode=KM_USE_FIRST_OCCURRENCE;
	public static final int KM_USE_FIRST_OCCURRENCE=1;
	public static final int KM_USE_LAST_OCCURRENCE=2;
	
	/**
	 * "Full" processing mode starts by setting all bits to false and only setting bits
	 * for documents that contain the given field and are identified as none-duplicates. 

	 * "Fast" processing sets all bits to true then unsets all duplicate docs found for the
	 * given field. This approach avoids the need to read TermDocs for terms that are seen 
	 * to have a document frequency of exactly "1" (i.e. no duplicates). While a potentially 
	 * faster approach , the downside is that bitsets produced will include bits set for 
	 * documents that do not actually contain the field given.
	 * 
	 */
	int processingMode=PM_FULL_VALIDATION;
	public static final int PM_FULL_VALIDATION=1;
	public static final int PM_FAST_INVALIDATION=2;
	

	
	public DuplicateFilter(String fieldName)
	{
		this(fieldName, KM_USE_LAST_OCCURRENCE,PM_FULL_VALIDATION);
	}
	

	public DuplicateFilter(String fieldName, int keepMode, int processingMode)
	{
		this.fieldName = fieldName;
		this.keepMode = keepMode;
		this.processingMode = processingMode;
	}

  @Override
  public DocIdSet getDocIdSet(IndexReader reader) throws IOException
	{
		if(processingMode==PM_FAST_INVALIDATION)
		{
			return fastBits(reader);
		}
		else
		{
			return correctBits(reader);
		}
	}
	
  private OpenBitSet correctBits(IndexReader reader) throws IOException
	{
		
    OpenBitSet bits=new OpenBitSet(reader.maxDoc()); //assume all are INvalid
		Term startTerm=new Term(fieldName);
		TermEnum te = reader.terms(startTerm);
		if(te!=null)
		{
			Term currTerm=te.term();
			while((currTerm!=null)&&(currTerm.field()==startTerm.field())) //term fieldnames are interned
			{
				int lastDoc=-1;
				//set non duplicates
				TermDocs td = reader.termDocs(currTerm);
				if(td.next())
				{
					if(keepMode==KM_USE_FIRST_OCCURRENCE)
					{
						bits.set(td.doc());
					}
					else
					{
						do
						{
							lastDoc=td.doc();
						}while(td.next());
						bits.set(lastDoc);
					}
				}
				if(!te.next())
				{
					break;
				}
				currTerm=te.term();
			}
		}
		return bits;
	}
	
  private OpenBitSet fastBits(IndexReader reader) throws IOException
	{
		
    OpenBitSet bits=new OpenBitSet(reader.maxDoc());
		bits.set(0,reader.maxDoc()); //assume all are valid
		Term startTerm=new Term(fieldName);
		TermEnum te = reader.terms(startTerm);
		if(te!=null)
		{
			Term currTerm=te.term();
			
			while((currTerm!=null)&&(currTerm.field()==startTerm.field())) //term fieldnames are interned
			{
				if(te.docFreq()>1)
				{
					int lastDoc=-1;
					//unset potential duplicates
					TermDocs td = reader.termDocs(currTerm);
					td.next();
					if(keepMode==KM_USE_FIRST_OCCURRENCE)
					{
						td.next();
					}
					do
					{
						lastDoc=td.doc();
            bits.clear(lastDoc);
					}while(td.next());
					if(keepMode==KM_USE_LAST_OCCURRENCE)
					{
						//restore the last bit
						bits.set(lastDoc);
					}					
				}
				if(!te.next())
				{
					break;
				}
				currTerm=te.term();
			}
		}
		return bits;
	}

	public String getFieldName()
	{
		return fieldName;
	}


	public void setFieldName(String fieldName)
	{
		this.fieldName = fieldName;
	}


	public int getKeepMode()
	{
		return keepMode;
	}


	public void setKeepMode(int keepMode)
	{
		this.keepMode = keepMode;
	}


	@Override
	public boolean equals(Object obj)
	{
		if(this == obj)
			return true;
		if((obj == null) || (obj.getClass() != this.getClass()))
			return false;
		DuplicateFilter other = (DuplicateFilter)obj;
		return keepMode == other.keepMode &&
		processingMode == other.processingMode &&
			(fieldName == other.fieldName || (fieldName != null && fieldName.equals(other.fieldName)));
	}



	@Override
	public int hashCode()
	{
		int hash = 217;
		hash = 31 * hash + keepMode;
		hash = 31 * hash + processingMode;
		hash = 31 * hash + fieldName.hashCode();
		return hash;	
	}


	public int getProcessingMode()
	{
		return processingMode;
	}


	public void setProcessingMode(int processingMode)
	{
		this.processingMode = processingMode;
	}
	
	

}

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