Bug 123726 "Top n", "Bottom n" in highlight dialog doesn't work.
Description: "Top n", "Bottom n" in highlight dialog doesn't work. Steps to reproduce: 1. Add a highlight for a table. 2. Set highlight rule: "account_id", "top n", "3", let its font color red. 3. Preview the report, it doesn't work. Attached is design file.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/PreparedQuery.java
* @param context
	 */
	protected void setAppContext( Map context )
	{
	    appContext = context;
	}
	
	/**
	 * @return the appropriate subclass of the Executor
	 */
	protected abstract Executor newExecutor();
	
	/**
	 * For a SubQuery, this returns the top-level data source query that
	 * contains the SubQuery. For other queries, "this" is returned
	 * 
	 * @return the main data source query
	 */
	abstract protected PreparedDataSourceQuery getDataSourceQuery();
	
	/**
	 * @throws DataException
	 */
	private void prepare( )	throws DataException
	{
	    
		Context cx = Context.enter();
		
		try
		{