Bug 416703 Mongodb : Display correctly the Number data type
data/org.eclipse.birt.data.oda.mongodb/src/org/eclipse/birt/data/oda/mongodb/internal/impl/MDbMetaData.java
*/
        public List<String> getSortedFieldNames()
        {
            Set<String> attributeNames = m_fieldsMetaData.keySet();
            return sortFieldNames( attributeNames );
        }
        private List<String> sortFieldNames( Set<String> fieldNames )
        {
            if( fieldNames == null || fieldNames.isEmpty() )
                return Collections.emptyList();
            
            String[] attrNamesArray = (String[])fieldNames.toArray( new String[fieldNames.size()] );
            Arrays.sort( attrNamesArray );
            List<String> sortedAttrList = new ArrayList<String>(attrNamesArray.length);
            sortedAttrList.addAll( Arrays.asList( attrNamesArray ) );
            return sortedAttrList;
        }
        
        public FieldMetaData getFieldMetaData( String fieldSimpleName )
        {
            FieldMetaData fieldMd = m_fieldsMetaData.get( fieldSimpleName );
            return fieldMd != null ? fieldMd : sm_emptyFieldMetaData;
        }
        public void setFlattenableFields( Map<String,FieldMetaData> resultFieldsMD, boolean isTopLevelDoc )
        {
            if( resultFieldsMD == null || resultFieldsMD.isEmpty() )
                return;     
            FieldMetaData flattenableFieldMD = null;
            if( m_nestedCollFieldName != null )
                flattenableFieldMD = resultFieldsMD.get( m_nestedCollFieldName );