Bug 196745 Data Engine implementation of BPS80- Result Set Sharing
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ResultIterator.java
if ( this.isFirstRowPepared )
			this.prepareCurrentRow( );
		
		if ( !this.boundColumnValueMap.containsKey( exprName ) )
		{
			
			
			if ( this.resultService.getBindingExpr( exprName ) != null )
			{
				return prepareBindingColumn( exprName );				
			}
			throw new DataException( ResourceConstants.INVALID_BOUND_COLUMN_NAME,
					exprName );
		}
		Object exprValue = boundColumnValueMap.get( exprName );
		if ( exprValue instanceof BirtException )
			throw (BirtException) exprValue;
		return exprValue;
	}
	
	/**
	 * Evaluate the specified column binding in case of its value still not
	 * calculate yet.
	 * 
	 * @param exprName
	 * @return
	 * @throws DataException