com.db4o.inside.query.NativeQueryHandler Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of db4o-java5 Show documentation
Db4o-java5
The newest version!
/* Copyright (C) 2004 - 2005  db4objects Inc.  http://www.db4o.com

This file is part of the db4o open source object database.

db4o is free software; you can redistribute it and/or modify it under
the terms of version 2 of the GNU General Public License as published
by the Free Software Foundation and as clarified by db4objects' GPL 
interpretation policy, available at
http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
Suite 350, San Mateo, CA 94403, USA.

db4o is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. */
package com.db4o.inside.query;

import com.db4o.*;
import com.db4o.foundation.*;
import com.db4o.query.*;

public class NativeQueryHandler {
	
	private static final String OPTIMIZER_IMPL_NAME = "com.db4o.nativequery.optimization.Db4oOnTheFlyEnhancer";

	public final static String UNOPTIMIZED = "UNOPTIMIZED";
	public final static String PREOPTIMIZED = "PREOPTIMIZED";
	public final static String DYNOPTIMIZED = "DYNOPTIMIZED";
	
	private ObjectContainer _container;
	private Db4oNQOptimizer _enhancer;
	private List4 _listeners;
	
	public NativeQueryHandler(ObjectContainer container) {
		_container = container;
		loadQueryOptimizer();
    }	

	public void addListener(Db4oQueryExecutionListener listener) {
		_listeners=new List4(_listeners,listener);
	}

	public void clearListeners() {
		_listeners=null;
	}
	
	public ObjectSet execute(Predicate predicate,QueryComparator comparator) {
		return configureQuery(predicate,comparator).execute();
	}
	
	private Query configureQuery(Predicate predicate,QueryComparator comparator) {
		Query q=_container.query();
		if(comparator!=null) {
			q.sortBy(comparator);
		}
		q.constrain(predicate.extentType());
		if(predicate instanceof Db4oEnhancedFilter) {
			((Db4oEnhancedFilter)predicate).optimizeQuery(q);
			notifyListeners(predicate,NativeQueryHandler.PREOPTIMIZED,null);
			return q;
		}
		try {
			if (_container.ext().configure().optimizeNativeQueries() && _enhancer!=null) {
				Object optimized=_enhancer.optimize(q,predicate);
				notifyListeners(predicate,NativeQueryHandler.DYNOPTIMIZED,optimized);
				return q;
			}
		} catch (Exception exc) {
			//exc.printStackTrace();
		}
		q.constrain(new PredicateEvaluation(predicate));
		notifyListeners(predicate,NativeQueryHandler.UNOPTIMIZED,null);
		return q;
	}

	private void notifyListeners(Predicate predicate, String msg,Object optimized) {
		NQOptimizationInfo info=new NQOptimizationInfo(predicate,msg,optimized);
		for(Iterator4 iter=new Iterator4Impl(_listeners);iter.hasNext();/**/) {
			((Db4oQueryExecutionListener)iter.next()).notifyQueryExecuted(info);
		}
	}
	
	private void loadQueryOptimizer() {
		try {
			Class enhancerClass = Class.forName(NativeQueryHandler.OPTIMIZER_IMPL_NAME);
			_enhancer=(Db4oNQOptimizer)enhancerClass.newInstance();
		} catch (Throwable ignored) {
			_enhancer=null;
		}
	}
}