How can I make sure that an existing value is not overwritten when doing an ElasticSearch update in-CodePudding

I have an ElasticSearch entry with the ID myId in the index myIndex. This entry has the field someExistingField.

Now I want to update this entry. For technical reasons, the update request does not contain someExistingField data.

I want to make sure that in scope of this update

only those values are changed that are specified in the update request and
values not mentioned in the update request are not changed.

Currently I am using this code:

final Map<String, Object> esDocument = ...;

final UpdateRequest request = new UpdateRequest(myIndex, myId);
request.doc(esDocument, XContentType.JSON);

esClient.update(request, RequestOptions.DEFAULT);

How do I need to change this code in order for it to not override existing values which are not specified in request?

CodePudding user response：

This seems to work:

final UpdateRequest request = new UpdateRequest(myIndex, myId);
...
request.fetchSource(new FetchSourceContext(true, 
  new String[]{"someExistingField"}, Strings.EMPTY_ARRAY));
...