Spring Elasticsearch-检索在字段中具有最大价值的文档

Question

I am looking for an elegant way to retrieve document that has largest value in a certain field of his. For example, I want to retrieve document that has largest timestamp. I've tried using aggregations, but it I could not manage to get it working, it would only return a field. I've also considered using sorting and the fetching the first element, but I find that a bit bruteforce. Such query would something like:

  SearchQuery searchQuery = new NativeSearchQueryBuilder()
            .withPageable(new PageRequest(0, 1))
            .withSort(SortBuilders.fieldSort(FIELD_TIMESTAMP)
                    .order(SortOrder.DESC))
            .build();

Is there any better way of doing such a task?

Answer 1

You can use size() method of SearchResponse to get the document with highest response.

For your query, it should be like this:

FieldSortBuilder timestampSort = SortBuilders.fieldSort(FIELD_TIMESTAMP).order(SortOrder.DESC);

SearchResponse response = client.prepareSearch(index)
            .addSort(timestampSort)
            .setSize(1)
            .execute()
            .actionGet();

Above query will return only one document, ie: first document from your query response.