Query or sort by @Reference association causes Mapping Exception - Invalid path reference <path>! Associations can only be pointed to directly or via their id property!

[caspian-borison-by]

When re-using @Document entities as embedded objects under another document, it can be desirable to disable auto-index creation for the embedded objects. Searching the internet turns up this stackoverflow link which seems to be the only way to get this desired behavior (ignore any defined indexes on Child class when creating Parent collection).

e.g.

@Document
class Parent {
   @Id String id;   
   @Reference Child child;
   @Reference List<Child> children;
}

@Document
class Child {
   @Id String id;
   String name;
}

However, you try to then query or sort parents via either above child/children path, it leads to an exception:

   // Any of these leads to the exception:
   mongoTemplate.find(Query.query(Criteria.where("child.name").is("blah")), ParentDocument.class);
   mongoTemplate.find(new Query().with(Sort.by("child.name")), ParentDocument.class);
   mongoTemplate.find(Query.query(Criteria.where("children.name").is("blah")), ParentDocument.class);
   mongoTemplate.find(new Query().with(Sort.by("children.name")), ParentDocument.class);

org.springframework.data.mapping.MappingException: Invalid path reference child.name! Associations can only be pointed to directly or via their id property!

	at org.springframework.data.mongodb.core.convert.QueryMapper$MetadataBackedField.getPath(QueryMapper.java:1224)
	at org.springframework.data.mongodb.core.convert.QueryMapper$MetadataBackedField.<init>(QueryMapper.java:1060)
	at org.springframework.data.mongodb.core.convert.QueryMapper$MetadataBackedField.<init>(QueryMapper.java:1037)
	at org.springframework.data.mongodb.core.convert.QueryMapper.createPropertyField(QueryMapper.java:340)
	at org.springframework.data.mongodb.core.convert.QueryMapper.mapFieldsToPropertyNames(QueryMapper.java:230)
	at org.springframework.data.mongodb.core.convert.QueryMapper.getMappedSort(QueryMapper.java:198)
	at org.springframework.data.mongodb.core.MongoTemplate.getMappedSortObject(MongoTemplate.java:2886)
	at org.springframework.data.mongodb.core.MongoTemplate.access$300(MongoTemplate.java:162)
	at org.springframework.data.mongodb.core.MongoTemplate$QueryCursorPreparer.prepare(MongoTemplate.java:3280)
	at org.springframework.data.mongodb.core.CursorPreparer.initiateFind(CursorPreparer.java:71)
	at org.springframework.data.mongodb.core.MongoTemplate.executeFindMultiInternal(MongoTemplate.java:2806)
	at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:2543)
	at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:2525)
	at org.springframework.data.mongodb.core.MongoTemplate.find(MongoTemplate.java:847)
	at org.springframework.data.mongodb.core.MongoTemplate.find(MongoTemplate.java:833)

I am unsure if this is or is not a a bug -- but it seems weird. I can understand why @DBRef would throw the above error, but I am uncertain why @Reference does? Alternatively, is there a different way to disable embedded object index creation when using IndexOperations?

[christophstrobl]

Please do not use an annotation that indicates an association between entities to prevent index creation, which is a different matter. In case autoindex does not work for you, consider to disable the feature and set up the index manually.
In the light of newly added @DocumentReference it still might make sense to relax the restriction.

[yihtserns]

Somewhat related to #2836.