如何使用Spring Data MongoDB查询无效引用的文档

Question

Let's assume that we have collection A which references collection B through a field called "bref", which is an array of ObjectId's from collection B. For collection A, there are 4 possible situations that I am interested in:

1. At least one bref array item points to a valid document from B.
2. The bref array is empty.
3. The bref array does not exist (is therefore null).
4. None of the items from bref array points to a valid B document.

In spring-data, using a MongoRepository, I was able to resolve the situations from above as follows:

1. getByBrefLike(ObjectId brefId, Pageable pageable)
2. getByBrefIsNullOrBrefIsLessThanEqual(String[] emptyString, Pageable pageable)
3. getByBrefIsNullOrBrefIsLessThanEqual(String[] emptyString, Pageable pageable)
4. Not solved yet.

Questions:

1. Is it possible to detect the documents from A that points to non-existent references from B, using spring-data mongodb repository like I did in the above example?
2. How would you prevent that situation from ever happening? (is it possible to define some constraints)?
3. If a spring-data solution is not possible, what would a mongodb solution look like?

Answer 1

尝试这个

Pageable<T> findByBrefNotIn(List<ObjectId> brefs, Pageable, pageable)