@Override
        protected Expression doConvert(Expression exp) {
            return new StatementExpression(
                    isArray ? new ForEachExpression(new ZCurveExpression()) :
                    new ZCurveExpression(), new AttributeExpression(replace));
        }
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