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78 lines
1.8 KiB
78 lines
1.8 KiB
#ifndef __Query_h__
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#define __Query_h__
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//
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// Query.h
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//
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// Query: (abstract) a parsed, 'executable' digger database query
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// a query tree is formed by leaf objects (ExactWordQuery) and
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// node objects (OperatorQuery) derived from this class.
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// Query execution results are returned as ResultList objects.
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// Query evaluation is cached. Cache policy is delegated to the
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// QueryCache class family.
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//
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// Part of the ht://Dig package <http://www.htdig.org/>
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// Copyright (c) 1995-2004 The ht://Dig Group
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// For copyright details, see the file COPYING in your distribution
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// or the GNU Library General Public License (LGPL) version 2 or later
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// <http://www.gnu.org/copyleft/lgpl.html>
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//
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// $Id: Query.h,v 1.4 2004/05/28 13:15:24 lha Exp $
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//
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//
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// for details about the basic architectural patterns see the book:
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// Design Patterns, by the infamous GoF
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// Interpreter pattern
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// Factory pattern
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// Flyweight pattern
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//
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#ifdef HAVE_CONFIG_H
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#include "htconfig.h"
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#endif
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#include "Object.h"
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#include "htString.h"
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#include "ResultList.h"
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class QueryCache;
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// abstract
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class Query : public Object
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{
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public:
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// destr
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virtual ~Query();
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// does nothing here -- hack for comfortable parser coding
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virtual void Add(Query *) {}
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// get a boolean-style query string
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virtual String GetLogicalWords() const = 0;
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// evaluate if necessary and return results
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ResultList *GetResults();
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// set a cache policy
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static void SetCache(QueryCache *c) { cache = c; }
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protected:
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// get an unique cache index
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virtual String GetSignature() const = 0;
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Query() {}
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// generate results
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virtual ResultList *Evaluate() = 0;
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// by default, nothing -- for use of leaf queries
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virtual void AdjustWeight(ResultList &) {}
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private:
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// the current cache object, if some
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static QueryCache *cache;
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};
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#endif
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