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* Copyright (C) 2003-2006 Ben van Klinken and the CLucene Team
* Distributable under the terms of either the Apache License (Version 2.0) or 
* the GNU Lesser General Public License, as specified in the COPYING file.
#ifndef _lucene_search_ChainedFilter_
#define _lucene_search_ChainedFilter_

#include "CLucene/index/IndexReader.h"
#include "CLucene/util/BitSet.h"
#include "CLucene/search/Filter.h"


Discussion - brian@unixpoet.com

From ChainedFilter.java:


// First AND operation takes place against a completely false
// bitset and will always return zero results. Thanks to
// Daniel Armbrust for pointing this out and suggesting workaround.

if (logic[0] == AND)
      result = (BitSet) chain[i].bits(reader).clone();


The observation is correct and it was buggy. The problem is that the same
issue remains for the ANDNOT logic op but with the inverse result: all bits
set to 1. The result of the other ops, i.e. OR, AND, XOR for the first filter
ends up just copying the bitset of the first filter (explicitly in the case of the AND).

Why not do the same for the NAND? This will have the side effect of rendering the first op
in the logic array superflous - not a big problem.

The only "problem" is that we will return different results then the Java 
Lucene code - though I prefer CLucene to be a correct implementation and only maintain 
API compat rather than full 100% compat with Lucene.  
class ChainedFilter: public Filter 
      LUCENE_STATIC_CONSTANT(int, OR            = 0); //set current bit if the chain is set OR if the filter bit is set
      LUCENE_STATIC_CONSTANT(int, AND     = 1); //set current bit if the chain is set AND the filter bit is set
      LUCENE_STATIC_CONSTANT(int, ANDNOT  = 2); //set current bit if the chain is not set AND the filter bit is not set
      LUCENE_STATIC_CONSTANT(int, XOR     = 3); //set current bit if the chain is set OR the filter bit is set BUT not both is set
      LUCENE_STATIC_CONSTANT(int, USER    = 5); //add this value to user defined value, then override doUserChain

      Filter **filters;
      int       *logicArray;
      int          logic;
      ChainedFilter( const ChainedFilter& copy );
      CL_NS(util)::BitSet* bits( CL_NS(index)::IndexReader* reader, int logic );
      CL_NS(util)::BitSet* bits( CL_NS(index)::IndexReader* reader, int* logicArray );
      CL_NS(util)::BitSet* doChain( CL_NS(util)::BitSet* result, CL_NS(index)::IndexReader* reader, int logic, Filter* filter );

      virtual void doUserChain( CL_NS(util)::BitSet* chain, CL_NS(util)::BitSet* filter, int logic );
      virtual const TCHAR* getLogicString(int logic);
      ChainedFilter( Filter** filters, int op = DEFAULT );
      ChainedFilter( Filter** filters, int* _array );
      virtual ~ChainedFilter();
      /** Returns a BitSet with true for documents which should be permitted in
      search results, and false for those that should not. */
      CL_NS(util)::BitSet* bits( CL_NS(index)::IndexReader* reader );

      virtual Filter* clone() const;
      TCHAR* toString();


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