public FieldMatchMetrics compute(Query query, String fieldString, boolean collectTrace) {
        return compute(query, new Field(fieldString), collectTrace);
    }
Computes the string match metrics from a query and field string.

@param query the query to compute over
@param fieldString the field value to compute over - tokenized by splitting on space
@param collectTrace true to accumulate trace information in the trace returned with the metrics
searchlib/src/main/java/com/yahoo/searchlib/ranking/features/fieldmatch/FieldMatchMetricsComputer.java