ES 5.1.X - REST API with SearchSourceBuilder bug?

[erik_dreyer]

I'm using the following in my Java project.

<!-- https://mvnrepository.com/artifact/org.elasticsearch.client/rest -->
<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>rest</artifactId>
    <version>5.1.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.elasticsearch/elasticsearch -->
<dependency>
    <groupId>org.elasticsearch</groupId>
    <artifactId>elasticsearch</artifactId>
    <version>5.1.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.elasticsearch.client/transport -->
<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>transport</artifactId>
    <version>5.1.1</version>
</dependency>

I'm using SearchSourceBuilder to build a query, which I then execute against the new REST API.

Specifically, I'm running a count query .../_count. The problem is that SearchSourceBuilder generates this as part of the query: { ..., ext:{} } which is not allows for /_count queries.

There seems to be no way to disable the generation of this field (null not allowed):

public SearchSourceBuilder ext(List<SearchExtBuilder> searchExtBuilders) {
    this.extBuilders = Objects.requireNonNull(searchExtBuilders, "searchExtBuilders must not be null");
    return this;
}

Is this a bug? Am I missing something? Or is there another preferred way to generate the queries?

Thanks,
Erik