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//
// OrQuery.cc
//
// OrQuery: an operator query that merges all the results of its operands
// i.e. does 'or' combination
//
// Part of the ht://Dig package <http://www.htdig.org/>
// Copyright (c) 1995-2004 The ht://Dig Group
// For copyright details, see the file COPYING in your distribution
// or the GNU Library General Public License (LGPL) version 2 or later
// <http://www.gnu.org/copyleft/lgpl.html>
//
// $Id: OrQuery.cc,v 1.4 2004/05/28 13:15:24 lha Exp $
//
#include "OrQuery.h"
//
// return a ResultList containing an Or of the results of the operands
// evaluate all operands to do so
//
// l r or
// ---------------------
// 0 0 0
// 0 b b
// 0 x x
// a 0 a
// a b union(a,b)
// a x a
// x 0 x
// x b b
// x x x
//
// i.e. nulls and ignored are left out union
//
// Note that all operands are evaluated
// Ignored operands are not included in the operation
// the longer input result list is passed separately to Union
//
ResultList *
OrQuery::Evaluate()
{
ResultList *result = 0;
ResultList *longer = 0;
List shorter;
int ignores = 0;
operands.Start_Get();
Query *operand = (Query *) operands.Get_Next();
while(operand)
{
ResultList *next = operand->GetResults();
if(next)
{
if(!next->IsIgnore())
{
if(!longer || longer->Count() < next->Count())
{
if(longer)
{
shorter.Add(longer);
}
longer = next;
}
else
{
shorter.Add(next);
}
}
else
{
ignores++;
}
}
operand = (Query *) operands.Get_Next();
}
if(longer)
{
result = Union(*longer, shorter);
shorter.Release();
}
else if(ignores == operands.Count())
{
result = new ResultList;
result->Ignore();
}
return result;
}
//
// copy unique DocMatches to the resulting list
// matches with the same docId are merged
// the longer list is assumed to be the first parameter
// this is a modest optimisation
//
ResultList *
OrQuery::Union(const ResultList &longer, const List &lists)
{
ResultList *result = new ResultList(longer);
ListCursor lc;
lists.Start_Get(lc);
ResultList *current = (ResultList *) lists.Get_Next(lc);
while(current)
{
DictionaryCursor c;
current->Start_Get(c);
DocMatch *match = (DocMatch *) current->Get_NextElement(c);
while(match)
{
DocMatch *previous = result->find(match->GetId());
if(previous)
{
previous->Merge(*match);
}
else
{
DocMatch *copy = new DocMatch(*match);
result->add(copy);
}
match = (DocMatch *) current->Get_NextElement(c);
}
current = (ResultList *) lists.Get_Next(lc);
}
return result;
}
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