question: public void accumulate ( TaggedLogAPIEntity entity ) throws Exception { AggregateAPIEntity current = root ; for ( String groupby : groupbys ) { String tagv = locateGroupbyField ( groupby , entity ) ; if ( tagv == null || tagv . isEmpty ( ) ) { tagv = UNASSIGNED_GROUPBY_ROOT_FIELD_NAME ; } Map < String , AggregateAPIEntity > children = current . getEntityList ( ) ; if ( children . get ( tagv ) == null ) { children . put ( tagv , factory . create ( ) ) ; current . setNumDirectDescendants ( current . getNumDirectDescendants ( ) + 1 ) ; } AggregateAPIEntity child = children . get ( tagv ) ; if ( counting ) count ( child ) ; for ( String sumFunctionField : sumFunctionFields ) { sum ( child , entity , sumFunctionField ) ; } current = child ; } }
target:  currently only group by tags groupbys' first item always is site, which is a reserved field 