[hibernate-issues] [JIRA] (HSEARCH-3974) Backend-specific extensions for scroll

Allow backends to extend the SearchScroll interfaces, like they currently do with SearchQuery ( ElasticsearchSearchQuery , LuceneSearchQuery ): * Add a generic parameter S extends SearchScroll<H> to ExtendedSearchFetchable and override its scroll methods to return that type. * Adapt the interfaces that extend ExtendedSearchFetchable as necessary. * Create a new ExtendedSearchScroll<H> interface using the same principle. * Create specific interfaces for Elasticsearch and Lucene: ElasticsearchSearchScroll and LuceneSearchScroll. * Implement these interfaces where appropriate. * Test extensions for Lucene and Elasticsearch. Mainly, check that the scroll has the correct type. See how it's done for SearchResult in org.hibernate.search.integrationtest.backend.elasticsearch.ElasticsearchExtensionIT#query .

Add Lucene-specific extensions to Scrolling * This is mainly necessary for Infinispan * Expose a way to force Lucene to extract TopDocs up to a specific index and retrieve them: LuceneSearchScroll#preloadTopDocsUpTo(), returns TopDocs * Expose a way to load a specific document specified by its index: LuceneSearchScroll#loadHitByIndex(), returns H * Maybe we can improve on that later; ideally Infinispan should load multiple hits in one call ( LuceneSearchScroll#loadHitsByIndex(int ...), returns List<H> ) otherwise the cost of creating collectors for each retrieved hit will be a bit too much.