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
.getReport( ) );
		
		executionContext.setReport( report );
		setParameterValues( reportDocReader.getParameterValues( ) );
		
		IDataEngine dataEngine = executionContext.getDataEngine();
		dataEngine.prepare( report, appContext );
	}
	
	/*
	 * prepare the meta data of DataExtractionTask.
	 */
	private void prepareMetaData( )
	{
		if( isMetaDataPrepared == true ) 
			return;
			
		mapQueryToReportItem = report.getReportItemToQueryMap( );
		mapQueryToValueExprs = report.getQueryToValueExprMap( );
		
		
		try
		{
			loadResultSetMetaData( );
		}
		catch( EngineException e )
		{
			e.printStackTrace( );
		}
		assert mapQueryIDToResultSetName != null;