Bug 213907 Provide a copy constructor for SubqueryDefinition.
Engine need a copy constructor to generate a SubqueryDefinition from an ISubqueryDefinition and change the name of the query.
data/org.eclipse.birt.report.data.adapter/src/org/eclipse/birt/report/data/adapter/api/DataRequestSession.java
throws BirtException;
	
	/**
	 * Provides a hint to DtE that the consumer is done with the given data
	 * source, and that its resources can be safely released as appropriate.
	 * This tells DtE that there is to be no more query in this session that
	 * uses such data source.
	 * 
	 * @param dataSourceName
	 *            The name of a data source. The named data source must have
	 *            been previously defined.
	 */
	public abstract void closeDataSource( String dataSourceName )
			throws BirtException;
	
	/**
	 * Delete the cache content of the specified data set. Subsequent requests
	 * using this data set will cause its cache to be regenerated with updated
	 * data
	 * 
	 * @param dataSource,
	 *            which is associated with the data set
	 * @param dataSet,
	 *            which cache needs to be cleared
	 * @throws BirtException
	 */
	public abstract void clearCache( IBaseDataSourceDesign dataSource,
			IBaseDataSetDesign dataSet ) throws BirtException;
	/**
	 * This method will return NULL if the named data set is not cached. Otherwise, it