Reindex API

A ReindexRequest can be used to copy documents from one or more indexes into a destination index.

It requires an existing source index and a target index which may or may not exist pre-request. Reindex does not attempt to set up the destination index. It does not copy the settings of the source index. You should set up the destination index prior to running a _reindex action, including setting up mappings, shard counts, replicas, etc.

The simplest form of a ReindexRequest looks like follows:

ReindexRequest request = new ReindexRequest(); 
request.setSourceIndices("source1", "source2"); 
request.setDestIndex("dest");  

The dest element can be configured like the index API to control optimistic concurrency control. Just leaving out versionType (as above) or setting it to internal will cause Elasticsearch to blindly dump documents into the target. Setting versionType to external will cause Elasticsearch to preserve the version from the source, create any documents that are missing, and update any documents that have an older version in the destination index than they do in the source index.

request.setDestVersionType(VersionType.EXTERNAL); 

Setting opType to create will cause _reindex to only create missing documents in the target index. All existing documents will cause a version conflict. The default opType is index.

request.setDestOpType("create"); 

By default version conflicts abort the _reindex process but you can just count them by settings it to proceed in the request body

request.setConflicts("proceed"); 

You can limit the documents by adding a type to the source or by adding a query.

request.setSourceDocTypes("doc"); 
request.setSourceQuery(new TermQueryBuilder("user", "kimchy")); 

It’s also possible to limit the number of processed documents by setting size.

request.setSize(10); 

By default _reindex uses batches of 1000. You can change the batch size with sourceBatchSize.

request.setSourceBatchSize(100); 

Reindex can also use the ingest feature by specifying a pipeline.

request.setDestPipeline("my_pipeline"); 

If you want a particular set of documents from the source index you’ll need to use sort. If possible, prefer a more selective query to size and sort.

request.addSortField("field1", SortOrder.DESC); 
request.addSortField("field2", SortOrder.ASC); 

ReindexRequest also supports a script that modifies the document. It allows you to also change the document’s metadata. The following example illustrates that.

request.setScript(
    new Script(
        ScriptType.INLINE, "painless",
        "if (ctx._source.user == 'kimchy') {ctx._source.likes++;}",
        Collections.emptyMap())); 

ReindexRequest supports reindexing from a remote Elasticsearch cluster. When using a remote cluster the query should be specified inside the RemoteInfo object and not using setSourceQuery. If both the remote info and the source query are set it results in a validation error during the request. The reason for this is that the remote Elasticsearch may not understand queries built by the modern query builders. The remote cluster support works all the way back to Elasticsearch 0.90 and the query language has changed since then. When reaching older versions, it is safer to write the query by hand in JSON.

request.setRemoteInfo(
    new RemoteInfo(
        "https", "localhost", 9002, null, new BytesArray(new MatchAllQueryBuilder().toString()),
        "user", "pass", Collections.emptyMap(), new TimeValue(100, TimeUnit.MILLISECONDS),
        new TimeValue(100, TimeUnit.SECONDS)
    )
); 

ReindexRequest also helps in automatically parallelizing using sliced-scroll to slice on _uid. Use setSlices to specify the number of slices to use.

request.setSlices(2); 

ReindexRequest uses the scroll parameter to control how long it keeps the "search context" alive.

request.setScroll(TimeValue.timeValueMinutes(10)); 

In addition to the options above the following arguments can optionally be also provided:

request.setTimeout(TimeValue.timeValueMinutes(2)); 

request.setRefresh(true); 

The asynchronous execution of a reindex request requires both the ReindexRequest instance and an ActionListener instance to be passed to the asynchronous method:

client.reindexAsync(request, RequestOptions.DEFAULT, listener); 

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 BulkByScrollResponse looks like:

ActionListener<BulkByScrollResponse> listener = new ActionListener<BulkByScrollResponse>() {
    @Override
    public void onResponse(BulkByScrollResponse bulkResponse) {
        
    }

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

The returned BulkByScrollResponse contains information about the executed operations and allows to iterate over each result as follows:

TimeValue timeTaken = bulkResponse.getTook(); 
boolean timedOut = bulkResponse.isTimedOut(); 
long totalDocs = bulkResponse.getTotal(); 
long updatedDocs = bulkResponse.getUpdated(); 
long createdDocs = bulkResponse.getCreated(); 
long deletedDocs = bulkResponse.getDeleted(); 
long batches = bulkResponse.getBatches(); 
long noops = bulkResponse.getNoops(); 
long versionConflicts = bulkResponse.getVersionConflicts(); 
long bulkRetries = bulkResponse.getBulkRetries(); 
long searchRetries = bulkResponse.getSearchRetries(); 
TimeValue throttledMillis = bulkResponse.getStatus().getThrottled(); 
TimeValue throttledUntilMillis = bulkResponse.getStatus().getThrottledUntil(); 
List<ScrollableHitSource.SearchFailure> searchFailures = bulkResponse.getSearchFailures(); 
List<BulkItemResponse.Failure> bulkFailures = bulkResponse.getBulkFailures();