Bug 124251 the data cann't been exported.
Description: the data cann't been exported. Steps to reproduce: 1. new a report 2. new a datasource and a data set(DS_A) 3. use an external library 4. drag a table to the report layout from the imported library 5. insert an another table into the layout of the report and bind the data set(DS_A) 6. preview in the 'Web Viewer' and export the data Actual result: The data can been exported. Expect result: The data can been exporteded
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/DataExtractionTask.java
parId = parId.getParentID();
					if( parId != null )
						queryResultName = parId.getDataSetName();
				}
				assert queryResultName != null;
				
				IQueryResults parentQueryResult = dataEngine
						.getQueryResults( queryResultName );
				assert parentQueryResult != null;
				
				IResultIterator iter = parentQueryResult.getResultIterator( );
				long rowid = dataSetId.getRowID( );
				
				int i = 0;
				while ( iter.next( ) && i++ < rowid ) 		;
				
				IResultIterator subIter = iter.getSecondaryIterator( dataSetId
						.getQueryName( ), executionContext.getScope( ) );
				
				currentResult = new ExtractionResults( subIter, 
						selectedColumns, getValueExpressions ( rptItem.getQuery( ) ) );
				return currentResult;
			}
			catch( BirtException be )
			{
				be.printStackTrace( );
			}
		}
		return null;
	}