Spring data - MongoDB : How to return a page/slice of only specific fields

Question

I want to implement pagination with scroll. My goal is to get a slice of data when scroll event is triggered.

My document "Foo" structure is relatively complex with a lot of nested objects. But I need to show only two fields from these documents.

I have two questions:

• In general, is specifying the fields in the query will enhance the performance? (seing that we dont get the whole document)

for example:

    @Query(value="{ path : ?0}", fields="{ path : 0 }")
    List<Foo> findByPath(String path);  

• If yes, How can I get a slice of documents with specific fields using "Pagebale"

    Slice<Foo> findSliceBy(Pageable pageable); 

Answer 1

When specifying the fields the performance is enhanced.

Just annotating the findSliceBy method with @Query will do the job

    @Query(fields="{path:1, name:1}")
   Slice<Foo> findSliceBy(Pageable pageable);