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#ifndef __Query_h__
#define __Query_h__
//
// Query.h
//
// Query: (abstract) a parsed, 'executable' digger database query
// a query tree is formed by leaf objects (ExactWordQuery) and
// node objects (OperatorQuery) derived from this class.
// Query execution results are returned as ResultList objects.
// Query evaluation is cached. Cache policy is delegated to the
// QueryCache class family.
//
// 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: Query.h,v 1.4 2004/05/28 13:15:24 lha Exp $
//
//
// for details about the basic architectural patterns see the book:
// Design Patterns, by the infamous GoF
// Interpreter pattern
// Factory pattern
// Flyweight pattern
//
#ifdef HAVE_CONFIG_H
#include "htconfig.h"
#endif
#include "Object.h"
#include "htString.h"
#include "ResultList.h"
class QueryCache;
// abstract
class Query : public Object
{
public:
// destr
virtual ~Query();
// does nothing here -- hack for comfortable parser coding
virtual void Add(Query *) {}
// get a boolean-style query string
virtual String GetLogicalWords() const = 0;
// evaluate if necessary and return results
ResultList *GetResults();
// set a cache policy
static void SetCache(QueryCache *c) { cache = c; }
protected:
// get an unique cache index
virtual String GetSignature() const = 0;
Query() {}
// generate results
virtual ResultList *Evaluate() = 0;
// by default, nothing -- for use of leaf queries
virtual void AdjustWeight(ResultList &) {}
private:
// the current cache object, if some
static QueryCache *cache;
};
#endif
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