Issue with aggregation LookupOperation - when we use _id vs id as foreign key

If you have following spring mongo data entities:

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document
public class Entity1 {
     @Id
    private String id;
}

and this entity :

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document
public class Entity2 {
     @Id
    private String id;
    private List<Entity1> entities1;
}

public class Entity2Full extends Entity2Full

Then following do NOT work:

        LookupOperation lookup = LookupOperation.newLookup()
                .from("entity1")
                .localField("entities1._id")
                .foreignField("_id")
                .as("entities1Full");

        ....       
        MatchOperation matchOperation = ...

        Aggregation agg = Aggregation.newAggregation(matchOperation, lookup);
        List<Entity2Full> user = mongoTemplate.aggregate(agg, Entity2.class, Entity2Full.class).getMappedResults(); // query Entity2 and link with Entity1

If I change the LookupOperation to :

        LookupOperation lookup = LookupOperation.newLookup()
                .from("entity2")
                .localField("entities1.id") //CHANGE _id to id
                .foreignField("id") //CHANGE _id to id
                .as("entities1Full");
       

Then it works.

E.g. changing “_id” to “id” in LookupOperation will make the above working - the issue is that on real mongo the _id works and id do not as it should be.

I have tried to put

    import org.springframework.data.mongodb.core.mapping.Field;

    @Field(name = "_id")
     @Id
    private String id;

on the id but this did not solve the issue - only when I put id and not _id it will work

[n4kong]

@jchobantonov-runbuggy Hi, i got same issue, and resolved by change mongodb version in the test application.properties

spring.mongodb.embedded.version=4.0.2

[sbg-sh]

@jchobantonov-runbuggy Hi, i got same issue, and resolved by change mongodb version in the test application.properties

spring.mongodb.embedded.version=4.0.2

Hello @n4kong , I have the same issue but it does not work for me, could you please tell more details.