and { only { filter_eq { all_rows ; built ; 12/1915 } } ; eq { hop { filter_eq { all_rows ; built ; 12/1915 } ; hr name } ; ( river garry ) } } = true
select the rows whose built record fuzzily matches to 121915 . there is only one such row in the table . the hr name record of this unqiue row is  river garry  .