使用spring数据elasticsearch和搜索相似文档，如何获得相似性分数？

Question

我正在使用最新版本的elasticsearch（在docker中）和spring boot（最新版本）应用程序，试图在其中搜索类似的文档。我的文档类有一个字符串字段：

@Field(
        name = "description",
        type = FieldType.Text,
        fielddata = true,
        analyzer = "icu_analyzer",
        termVector = TermVector.with_positions_offsets,
        similarity = Similarity.BM25)
private String description;

当我使用内置的search ch相似方法时，我的查询得到了很多结果：

public Page<BookInfo> findSimilarDocuments(final long id) {
    return bookInfoRepository.findById(id)
            .map(bookInfo -> bookInfoRepository.searchSimilar(bookInfo, new String[]{"description"}, pageable))
            .orElse(Page.empty());
}

然而，我不知道这些文档有多相似，因为它只是我的文档对象的一个页面。在执行查询时，能够看到相似性分数或设置相似性阈值将非常棒。我应该做些不同的事情吗？

Answer 1

我刚刚看了一下，现有的方法页面

public Page<T> searchSimilar(T entity, @Nullable String[] fields, Pageable pageable) {

    Assert.notNull(entity, "Cannot search similar records for 'null'.");
    Assert.notNull(pageable, "'pageable' cannot be 'null'");

    MoreLikeThisQuery query = new MoreLikeThisQuery();
    query.setId(stringIdRepresentation(extractIdFromBean(entity)));
    query.setPageable(pageable);

    if (fields != null) {
        query.addFields(fields);
    }

    SearchHits<T> searchHits = execute(operations -> operations.search(query, entityClass, getIndexCoordinates()));
    SearchPage<T> searchPage = SearchHitSupport.searchPageFor(searchHits, pageable);
    return (Page<T>) SearchHitSupport.unwrapSearchHits(searchPage);
}

您可以实现自定义存储库片段（请参见https://docs.spring.io/spring-data/elasticsearch/docs/4.2.6/reference/html/#repositories.custom-实现），它提供了返回搜索页面的方法的自身实现

public SearchPage<T> searchSimilar(T entity, @Nullable String[] fields, Pageable pageable) {

    Assert.notNull(entity, "Cannot search similar records for 'null'.");
    Assert.notNull(pageable, "'pageable' cannot be 'null'");

    MoreLikeThisQuery query = new MoreLikeThisQuery();
    query.setId(stringIdRepresentation(extractIdFromBean(entity)));
    query.setPageable(pageable);

    if (fields != null) {
        query.addFields(fields);
    }

    SearchHits<T> searchHits = execute(operations -> operations.search(query, entityClass, getIndexCoordinates()));
    SearchPage<T> searchPage = SearchHitSupport.searchPageFor(searchHits, pageable);
    return searchPage;
}

一个搜索页面