Elastic / NEST将不处理空值

Question

I am currently limited to NEST v2.4.6.

I have objects with attributes that can sometimes be null and must be persisted with those null attributes.

According to the documentation: https://www.elastic.co/guide/en/elasticsearch/client/net-api/2.x/modifying-default-serializer.html#_modifying_settings_using_serializerfactory

This should allow me to serialize Null values. Unfortunately, once setting this up, all my ElasticDB queries start to return nothing.

This is confusing as when I put the

[JsonProperty(NullValueHandling = NullValueHandling.Include)]

attribute, it works fine.

I obviously however would like to enable this globally.

This is what my implementation looks like:

    var pool = new SingleNodeConnectionPool(new Uri(ConfigurationManager.AppSettings["ElasticInstanceAddress"]));
    var connection = new HttpConnection();
    var settings = new ConnectionSettings(pool, connection,
        new SerializerFactory((s, values) =>
    {
        s.NullValueHandling = NullValueHandling.Include;
    }));

An example NEST query that suddenly starts to return nothing after the NullValueHandling is enabled on the serializer is as below:

var dog = _client.Get<Dog>(query.DogName).Source;

Any ideas?

Answer 1

Why should your object be persisted with null values? Persisted or not, the value should be null when deserialized back from _source because the field is either missing or actually set to null . In any case, it should work by default. Checking for null in a query can be done with an Exists Query, see : https://www.elastic.co/guide/en/elasticsearch/reference/2.4/query-dsl-exists-query.html