private void appendNewFields(Fields fields) {
            properties.putAll(fields.properties);
            Set<String> inputExcludes = fields.source.getExcludes();
            Set<String> excludes = source.getExcludes();
            excludes.addAll(inputExcludes);
            fields.properties.keySet().forEach(p -> {
                if (!inputExcludes.contains(p) && excludes.contains(p)) {
                    excludes.remove(p);
                }
            });
        }
Append new fields and update.
Properties combine input and exist, update property's attribute, won't remove old one.
If the existed `excludes` contains a not existing property, the excluded field would be removed.
oap-server/server-storage-plugin/storage-elasticsearch-plugin/src/main/java/org/apache/skywalking/oap/server/storage/plugin/elasticsearch/base/IndexStructures.java