Multi-Get API
editMulti-Get API
editThe multiGet
API executes multiple get
requests in a single http request in parallel.
Multi-Get Request
editA MultiGetRequest
is built empty and you add `MultiGetRequest.Item`s to configure
what to fetch:
Optional arguments
editmultiGet
supports the same optional arguments that the
get
API supports.
You can set most of these on the Item
:
request.add(new MultiGetRequest.Item("index", "example_id") .fetchSourceContext(FetchSourceContext.DO_NOT_FETCH_SOURCE));
String[] includes = new String[] {"foo", "*r"}; String[] excludes = Strings.EMPTY_ARRAY; FetchSourceContext fetchSourceContext = new FetchSourceContext(true, includes, excludes); request.add(new MultiGetRequest.Item("index", "example_id") .fetchSourceContext(fetchSourceContext));
String[] includes = Strings.EMPTY_ARRAY; String[] excludes = new String[] {"foo", "*r"}; FetchSourceContext fetchSourceContext = new FetchSourceContext(true, includes, excludes); request.add(new MultiGetRequest.Item("index", "example_id") .fetchSourceContext(fetchSourceContext));
request.add(new MultiGetRequest.Item("index", "example_id") .storedFields("foo")); MultiGetResponse response = client.mget(request, RequestOptions.DEFAULT); MultiGetItemResponse item = response.getResponses()[0]; String value = item.getResponse().getField("foo").getValue();
Configure retrieval for specific stored fields (requires fields to be stored separately in the mappings) |
|
Retrieve the |
request.add(new MultiGetRequest.Item("index", "with_routing") .routing("some_routing")); request.add(new MultiGetRequest.Item("index", "with_version") .versionType(VersionType.EXTERNAL) .version(10123L));
preference
,
realtime
and
refresh
can be set on the main request but
not on any items:
Synchronous execution
editWhen executing a MultiGetRequest
in the following manner, the client waits
for the MultiGetResponse
to be returned before continuing with code execution:
MultiGetResponse response = client.mget(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 execution
editExecuting a MultiGetRequest
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 multi-get method:
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 multi-get
looks like:
Multi Get Response
editThe returned MultiGetResponse
contains a list of MultiGetItemResponse`s in
`getResponses
in the same order that they were requested.
MultiGetItemResponse
contains either a
GetResponse
if the get succeeded
or a MultiGetResponse.Failure
if it failed. A success looks just like a
normal GetResponse
.
MultiGetItemResponse firstItem = response.getResponses()[0]; assertNull(firstItem.getFailure()); GetResponse firstGet = firstItem.getResponse(); String index = firstItem.getIndex(); String id = firstItem.getId(); if (firstGet.isExists()) { long version = firstGet.getVersion(); String sourceAsString = firstGet.getSourceAsString(); Map<String, Object> sourceAsMap = firstGet.getSourceAsMap(); byte[] sourceAsBytes = firstGet.getSourceAsBytes(); } else { }
|
|
|
|
Retrieve the document as a |
|
Retrieve the document as a |
|
Retrieve the document as a |
|
Handle the scenario where the document was not found. Note that although
the returned response has |
When one of the subrequests as performed against an index that does not exist
getFailure
will contain an exception:
assertNull(missingIndexItem.getResponse()); Exception e = missingIndexItem.getFailure().getFailure(); ElasticsearchException ee = (ElasticsearchException) e; // TODO status is broken! fix in a followup // assertEquals(RestStatus.NOT_FOUND, ee.status()); assertThat(e.getMessage(), containsString("reason=no such index [missing_index]"));
|
|
|
|
That |
|
and it has a status of |
|
|
In case a specific document version has been requested, and the existing document has a different version number, a version conflict is raised:
MultiGetRequest request = new MultiGetRequest(); request.add(new MultiGetRequest.Item("index", "example_id") .version(1000L)); MultiGetResponse response = client.mget(request, RequestOptions.DEFAULT); MultiGetItemResponse item = response.getResponses()[0]; assertNull(item.getResponse()); Exception e = item.getFailure().getFailure(); ElasticsearchException ee = (ElasticsearchException) e; // TODO status is broken! fix in a followup // assertEquals(RestStatus.CONFLICT, ee.status()); assertThat(e.getMessage(), containsString("version conflict, current version [1] is " + "different than the one provided [1000]"));