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Elastic Docs ›Java REST Client [6.4] ›Java High Level REST Client ›Indices APIs

Force Merge API

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Force Merge API

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Force merge Request

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A ForceMergeRequest can be applied to one or more indices, or even on _all the indices:

ForceMergeRequest request = new ForceMergeRequest("index1"); 
ForceMergeRequest requestMultiple = new ForceMergeRequest("index1", "index2"); 
ForceMergeRequest requestAll = new ForceMergeRequest();

Force merge one index

Force merge multiple indices

Force merge all the indices

Optional arguments

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request.indicesOptions(IndicesOptions.lenientExpandOpen());

Setting IndicesOptions controls how unavailable indices are resolved and how wildcard expressions are expanded

 
request.maxNumSegments(1);

Set max_num_segments to control the number of segments to merge down to.

 
request.onlyExpungeDeletes(true);

Set the only_expunge_deletes flag to true

 
request.flush(true);

Set the flush flag to true

Synchronous Execution

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ForceMergeResponse forceMergeResponse = client.indices().forcemerge(request, RequestOptions.DEFAULT);

Asynchronous Execution

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The asynchronous execution of a force merge request requires both the ForceMergeRequest instance and an ActionListener instance to be passed to the asynchronous method:

client.indices().forcemergeAsync(request, RequestOptions.DEFAULT, listener);

The ForceMergeRequest 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.

A typical listener for ForceMergeResponse looks like:

ActionListener<ForceMergeResponse> listener = new ActionListener<ForceMergeResponse>() {
    @Override
    public void onResponse(ForceMergeResponse forceMergeResponse) {
        
    }

    @Override
    public void onFailure(Exception e) {
        
    }
};

Called when the execution is successfully completed. The response is provided as an argument

Called in case of failure. The raised exception is provided as an argument

Force Merge Response

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The returned ForceMergeResponse allows to retrieve information about the executed operation as follows:

int totalShards = forceMergeResponse.getTotalShards(); 
int successfulShards = forceMergeResponse.getSuccessfulShards(); 
int failedShards = forceMergeResponse.getFailedShards(); 
DefaultShardOperationFailedException[] failures = forceMergeResponse.getShardFailures();

Total number of shards hit by the force merge request

Number of shards where the force merge has succeeded

Number of shards where the force merge has failed

A list of failures if the operation failed on one or more shards

By default, if the indices were not found, an ElasticsearchException will be thrown:

try {
    ForceMergeRequest request = new ForceMergeRequest("does_not_exist");
    client.indices().forcemerge(request, RequestOptions.DEFAULT);
} catch (ElasticsearchException exception) {
    if (exception.status() == RestStatus.NOT_FOUND) {
        
    }
}

Do something if the indices to be force merged were not found
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