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DATAES-766 - Replace CloseableIterator with SearchHitsIterator in str… #412

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Mar 27, 2020
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DATAES-766 - Replace CloseableIterator with SearchHitsIterator in str… #412

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35 changes: 17 additions & 18 deletions src/main/asciidoc/reference/elasticsearch-misc.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -27,10 +27,8 @@ Page<SampleEntity> sampleEntities = operations.searchForPage(searchQuery, Sample
[[elasticsearch.scroll]]
== Using Scroll For Big Result Set

Elasticsearch has a scroll API for getting big result set in chunks. `ElasticsearchOperations` has startScroll and continueScroll methods that can be used as below.
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.

.Using startScroll and continueScroll
====
[source,java]
----
IndexCoordinates index = IndexCoordinates.of("sample-index");
Expand All @@ -43,25 +41,23 @@ SearchQuery searchQuery = new NativeSearchQueryBuilder()
.withPageable(PageRequest.of(0, 10))
.build();

ScrolledPage<SampleEntity> scroll = operations.startScroll(1000, searchQuery, SampleEntity.class, index);
SearchHitsIterator<SampleEntity> stream = elasticsearchTemplate.searchForStream(searchQuery, SampleEntity.class, index);

String scrollId = scroll.getScrollId();
List<SampleEntity> sampleEntities = new ArrayList<>();
while (scroll.hasContent()) {
sampleEntities.addAll(scroll.getContent());
scrollId = scroll.getScrollId();
scroll = operations.continueScroll(scrollId, 1000, SampleEntity.class);
while (stream.hasNext()) {
sampleEntities.add(stream.next());
}
operations.clearScroll(scrollId);

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

`ElasticsearchOperations` additionally has the stream method which wraps the scan and scroll operations into a CloseableIterator.
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:

.Using stream
====
[source,java]
----

@Autowired ElasticsearchRestTemplate template;

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

SearchQuery searchQuery = new NativeSearchQueryBuilder()
Expand All @@ -72,14 +68,17 @@ SearchQuery searchQuery = new NativeSearchQueryBuilder()
.withPageable(PageRequest.of(0, 10))
.build();

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

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

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