spring-data-elasticsearch/src/main/asciidoc/reference/elasticsearch-misc.adoc

[[elasticsearch.misc]]
= Miscellaneous Elasticsearch Operation Support

This chapter covers additional support for Elasticsearch operations that cannot be directly accessed via the repository interface.
It is recommended to add those operations as custom implementation as described in <<repositories.custom-implementations>> .

[[elasticsearc.misc.index.settings]]
== Index settings

When creating Elasticsearch indices with Spring Data Elasticsearch different index settings can be defined by using the `@Setting` annotation. The following arguments are available:

* `useServerConfiguration` does not send any settings parameters, so the Elasticsearch server configuration determines them.
* `settingPath` refers to a JSON file defining the settings that must be resolvable in the classpath
* `shards` the number of shards to use, defaults to _1_
* `replicas` the number of replicas, defaults to _1_
* `refreshIntervall`, defaults to _"1s"_
* `indexStoreType`, defaults to _"fs"_


It is as well possible to define https://www.elastic.co/guide/en/elasticsearch/reference/7.11/index-modules-index-sorting.html[index sorting] (check the linked Elasticsearch documentation for the possible field types and values):

====
[source,java]
----
@Document(indexName = "entities")
@Setting(
  sortFields = { "secondField", "firstField" },                                  <.>
  sortModes = { Setting.SortMode.max, Setting.SortMode.min },                    <.>
  sortOrders = { Setting.SortOrder.desc, Setting.SortOrder.asc },
  sortMissingValues = { Setting.SortMissing._last, Setting.SortMissing._first })
class Entity {
    @Nullable
    @Id private String id;

    @Nullable
    @Field(name = "first_field", type = FieldType.Keyword)
    private String firstField;

    @Nullable @Field(name = "second_field", type = FieldType.Keyword)
    private String secondField;

    // getter and setter...
}
----
<.> when defining sort fields, use the name of the Java property (_firstField_), not the name that might be defined for Elasticsearch (_first_field_)
<.> `sortModes`, `sortOrders` and `sortMissingValues` are optional, but if they are set, the number of entries must match the number of `sortFields` elements
====

[[elasticsearch.misc.filter]]
== Filter Builder

Filter Builder improves query speed.

====
[source,java]
----
private ElasticsearchOperations operations;

IndexCoordinates index = IndexCoordinates.of("sample-index");

SearchQuery searchQuery = new NativeSearchQueryBuilder()
  .withQuery(matchAllQuery())
  .withFilter(boolFilter().must(termFilter("id", documentId)))
  .build();

Page<SampleEntity> sampleEntities = operations.searchForPage(searchQuery, SampleEntity.class, index);
----
====

[[elasticsearch.scroll]]
== Using Scroll For Big Result Set

Elasticsearch has a scroll API for getting big result set in chunks.
This is internally used by Spring Data Elasticsearch to provide the implementations of the `<T> SearchHitsIterator<T> SearchOperations.searchForStream(Query query, Class<T> clazz, IndexCoordinates index)` method.

====
[source,java]
----
IndexCoordinates index = IndexCoordinates.of("sample-index");

SearchQuery searchQuery = new NativeSearchQueryBuilder()
  .withQuery(matchAllQuery())
  .withFields("message")
  .withPageable(PageRequest.of(0, 10))
  .build();

SearchHitsIterator<SampleEntity> stream = elasticsearchTemplate.searchForStream(searchQuery, SampleEntity.class, index);

List<SampleEntity> sampleEntities = new ArrayList<>();
while (stream.hasNext()) {
  sampleEntities.add(stream.next());
}

stream.close();
----
====

There are no methods in the `SearchOperations` API to access the scroll id, if it should be necessary to access this, the following methods of the `ElasticsearchRestTemplate` can be used:

====
[source,java]
----

@Autowired ElasticsearchRestTemplate template;

IndexCoordinates index = IndexCoordinates.of("sample-index");

SearchQuery searchQuery = new NativeSearchQueryBuilder()
  .withQuery(matchAllQuery())
  .withFields("message")
  .withPageable(PageRequest.of(0, 10))
  .build();

SearchScrollHits<SampleEntity> scroll = template.searchScrollStart(1000, searchQuery, SampleEntity.class, index);

String scrollId = scroll.getScrollId();
List<SampleEntity> sampleEntities = new ArrayList<>();
while (scroll.hasSearchHits()) {
  sampleEntities.addAll(scroll.getSearchHits());
  scrollId = scroll.getScrollId();
  scroll = template.searchScrollContinue(scrollId, 1000, SampleEntity.class);
}
template.searchScrollClear(scrollId);
----
====

To use the Scroll API with repository methods, the return type must defined as `Stream` in the Elasticsearch Repository.
The implementation of the method will then use the scroll methods from the ElasticsearchTemplate.

====
[source,java]
----
interface SampleEntityRepository extends Repository<SampleEntity, String> {

    Stream<SampleEntity> findBy();

}
----
====

[[elasticsearch.misc.sorts]]
== Sort options

In addition to the default sort options described <<repositories.paging-and-sorting>> Spring Data Elasticsearch has a `GeoDistanceOrder` class which can be used to have the result of a search operation ordered by geographical distance.

If the class to be retrieved has a `GeoPoint` property named _location_, the following `Sort` would sort the results by distance to the given point:

====
[source,java]
----
Sort.by(new GeoDistanceOrder("location", new GeoPoint(48.137154, 11.5761247)))
----
====