Preview transform APIedit

Previews the results of a transform.

The API accepts a PreviewTransformRequest object as a request and returns a PreviewTransformResponse.

Preview transform requestedit

A PreviewTransformRequest takes a single argument: a valid transform config.

TransformConfig transformConfig =

PreviewTransformRequest request =
        new PreviewTransformRequest(transformConfig); 

The source config from which the data should be gathered

The pivot config used to transform the data

The configuration of the transform to preview

Synchronous executionedit

When executing a PreviewTransformRequest in the following manner, the client waits for the PreviewTransformResponse to be returned before continuing with code execution:

PreviewTransformResponse response =
        .previewTransform(request, RequestOptions.DEFAULT);

Synchronous calls may throw an IOException in case of either failing to parse the REST response in the high-level REST client, the request times out or similar cases where there is no response coming back from the server.

In cases where the server returns a 4xx or 5xx error code, the high-level client tries to parse the response body error details instead and then throws a generic ElasticsearchException and adds the original ResponseException as a suppressed exception to it.

Asynchronous executionedit

Executing a PreviewTransformRequest can also be done in an asynchronous fashion so that the client can return directly. Users need to specify how the response or potential failures will be handled by passing the request and a listener to the asynchronous preview-transform method:

        request, RequestOptions.DEFAULT, listener);  

The PreviewTransformRequest to execute and the ActionListener to use when the execution completes

The asynchronous method does not block and returns immediately. Once it is completed the ActionListener is called back using the onResponse method if the execution successfully completed or using the onFailure method if it failed. Failure scenarios and expected exceptions are the same as in the synchronous execution case.

A typical listener for preview-transform looks like:

ActionListener<PreviewTransformResponse> listener =
    new ActionListener<PreviewTransformResponse>() {
        public void onResponse(PreviewTransformResponse response) {

        public void onFailure(Exception e) {

Called when the execution is successfully completed.

Called when the whole PreviewTransformRequest fails.


The returned PreviewTransformResponse contains the preview documents