ElasticSearch NEST API update value to null

问题:

I am using NEST api and I am having trouble using client.Update<T, K> method to update a value to null

Is there any parameter or settings when calling update that will allow for null to be set trough nest api?

I know I can do it with sense.

回答1:

Rather then changing how null should be serialised for the entire request the safest and most isolated way to do this is to introduce a separate POCO for the update where the property you want to clear has the following attribute.

[JsonProperty(NullValueHandling = NullValueHandling.Include)]

Example POCO:

// <summary>
/// This POCO models an ElasticsearchProject that allows country to serialize to null explicitly
/// So that we can use it to clear contents in the Update API
/// </summary>
public class PartialElasticsearchProjectWithNull
{
    [JsonProperty(NullValueHandling = NullValueHandling.Include)]
    public string Country { get; set; }
}

Example update using that POCO:

var partialUpdate = new PartialElasticsearchProjectWithNull { Country = null };

this._client.Update<ElasticsearchProject, PartialElasticsearchProjectWithNull>(update => update
    .Id(3) 
    .Doc(partialUpdate)
);

which will generate the following JSON:

{
  "doc": {
    "country": null
  }
}

回答2:

• In my case, I had a .NET DateTime? property, and I wanted to update an ElasticSearch date property to either null or empty.
• I couldn't do it with the Doc method. It wouldn't push my null assignment to elasticsearch (probably because the elasticsearch date type doesn't support null).

So here's what I did:

1. I modified the elasticsearch.yml file to include this setting: script.groovy.sandbox.enabled: true.

2. I modified my C# code to the following to remove the property from the document:

       _elasticClient.Update<MyIndexType, object>(u => u
           .Id(myDocumentId)
           .Index(myIndexName)
           .Type(myType)
           .Script(string.Format("ctx._source.remove(\"{0}\")", myPropertyName))
           .RetryOnConflict(3));