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.tests/test/org/eclipse/birt/data/engine/binding/APITestCase.java
{
		try
		{
			Object val = result.getValue( name );
			if ( val == null )
				return "<null>";
			else
				return val.toString( );
		}
		catch ( Exception e )
		{
			
			
			return "<EXCEPTION>";
		}
	}
	
	/**
	 * Return default query definition
	 * 
	 * @param dataSetName
	 * @return default query definition
	 */
	protected IQueryDefinition getDefaultQueryDefn( String dataSetName )
	{
		return Util.instance.getDefaultQueryDefn( dataSetName );
	}
	
	/**
	 * Return default query definition with subquery