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//
// Query.cc
//
// 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 <https://htdig.sourceforge.net/>
// 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.cc,v 1.4 2004/05/28 13:15:24 lha Exp $
//
#include "Query.h"
#include "VolatileCache.h"
//
// the in-memory query result cache. the default instance is
// defined static so its destructor is called at program exit
//
VolatileCache theDefaultCache;
QueryCache *
Query::cache = &theDefaultCache;
extern int debug;
//
// destructor
//
Query::~Query()
{
}
//
// return a ResultList with the query results
// results are initially fetched from the cache
// if not cached, the query is evaluated
// Weight of the results is adjusted at each invocation, as
// the same result list may be shared by different queries
// but different weights may be assigned to the word
//
//
ResultList *
Query::GetResults()
{
ResultList *result = 0;
// try to find in cache before trying eval
String signature;
if(cache)
{
signature = GetSignature();
result = cache->Lookup(signature);
}
// no cache or not in cache, evaluate
if(!result)
{
if(debug) cerr << "EVAL: " << signature << endl;
result = Evaluate();
if(cache)
{
cache->Add(signature, result);
}
}
// adjust if something found/returned
if(result)
{
if(result->Count())
{
AdjustWeight(*result);
}
else if(!result->IsIgnore())
{
result = 0;
}
}
return result;
}
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