elasticsearch-misc.adoc

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] .

Filter Builder

Filter Builder improves query speed.

private ElasticsearchTemplate elasticsearchTemplate;

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

Page<SampleEntity> sampleEntities =
    elasticsearchTemplate.queryForPage(searchQuery,SampleEntity.class);

Using Scroll For Big Result Set

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

Example 1. Using startScroll and continueScroll

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

ScrolledPage<SampleEntity> scroll = elasticsearchTemplate.startScroll(1000, searchQuery, SampleEntity.class);

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

ElasticsearchTemplate additionally has the stream method which wraps the scan and scroll operations into a CloseableIterator.

Example 2. Using stream

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

CloseableIterator<SampleEntity> stream = elasticsearchTemplate.stream(searchQuery, SampleEntity.class);

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