Bug 123576 Data can't be retrieved when exporting data
Description: Data can't be retrieved when exporting data Steps to reproduce: 1.Preview the attached file in Web Viewer 2.Exported the data in table Expected result: The data is exported as a CSV file Actual result: No data is retrieved
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/DataExtractionTask.java
{
			IBaseQueryDefinition query = (IBaseQueryDefinition)mapResultSetNameToQuery
									.get( resultSetName );
			assert query != null;
			validateSelectedColumns( query );
			
			IQueryResults queryResults = dataEngine.getQueryResults( resultSetName );
			assert queryResults.getResultIterator() != null;
			 
			currentResult = new ExtractionResults( queryResults.getResultIterator() 
					, selectedColumns, getValueExpressions( query ) );
			return currentResult;
		}
		catch ( BirtException e )
		{
			e.printStackTrace( );
		}
		return null;
	}
	
	/*
	 * data export by report item instance
	 */
	private IExtractionResults extractByInstanceId( ) throws EngineException
	{
		assert instanceId != null;
		
		assert executionContext.getDataEngine() != null;
		DataEngine dataEngine = executionContext.getDataEngine().getDataEngine();