private static Dictionary.Type extractDictionaryType(Attribute attr) {
        Dictionary dict = attr.getDictionary();
        return dict != null ? dict.getType() : Dictionary.Type.BTREE;
    }
Validates the changes between the current and next set of attribute fields in a document database.

@author geirst
config-model/src/main/java/com/yahoo/vespa/model/application/validation/change/search/AttributeChangeValidator.java