private Set<String> removeSummaryTo(SDField field) {
        Set<String> summaryTo = new HashSet<>();
        Collection<SummaryField> summaryFields = field.getSummaryFields().values();
        for (SummaryField summary : summaryFields) {
            summaryTo.addAll(summary.getDestinations());
        }
        field.removeSummaryFields();
        return summaryTo;
    }
Adds a "fieldName_zcurve" long attribute and "fieldName.distance" and "FieldName.position" summary fields to all position type fields.

@author bratseth
config-model/src/main/java/com/yahoo/schema/processing/CreatePositionZCurve.java