Bug 180842 Config memory buffer size in data engine execution.
To tuning the performance, it is necessary for DtE to expose API for clients to config the size of memory it used to store the final result set. A new AppContext string, "org.eclipse.birt.data.cache.memory.size" is proposed. The new appcontext entry only accept positive integer as input, the unit of which would be MB.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ServiceForQueryResults.java
*/
	public IBaseQueryDefinition getQueryDefn( )
	{
		return queryDefn;
	}
	/*
	 * @see org.eclipse.birt.data.engine.impl.IQueryService#getPreparedQuery()
	 */
	public IPreparedQuery getPreparedQuery( )
	{
		return this.reportQuery;
	}
	
	/*
	 * @see org.eclipse.birt.data.engine.impl.IQueryService#getGroupLevel()
	 */
	public int getGroupLevel( )
	{
		if ( queryService instanceof PreparedSubquery )
		{
			PreparedSubquery subQuery = (PreparedSubquery) queryService;
			return subQuery.getGroupLevel( );
		}
		else if ( queryService instanceof PreparedIVSubQuery )
		{
			PreparedIVSubQuery subQuery = (PreparedIVSubQuery) queryService;
			return subQuery.getGroupLevel( );
		}
		else
		{