Update some specific field of an entity in android Room

Question

I am using android room persistence library for my new project. I want to update some field of table. I have tried like in my Dao -

// Method 1:

@Dao
public interface TourDao {
    @Update
    int updateTour(Tour tour);
}

But when I try to update using this method then it updates every field of the entity where it matches primary key value of tour object. I have used @Query

// Method 2:

@Query("UPDATE Tour SET endAddress = :end_address WHERE id = :tid")
int updateTour(long tid, String end_address);

It is working but there will be many queries in my case because I have many fields in my entity. I want to know how can I update some field (not all) like Method 1 where id = 1; (id is the auto generate primary key).

// Entity:

@Entity
public class Tour {
    @PrimaryKey(autoGenerate = true)
    public long id;
    private String startAddress;
    private String endAddress;
    //constructor, getter and setter
}

Answer 1

I want to know how can I update some field(not all) like method 1 where id = 1

Use @Query, as you did in Method 2.

is too long query in my case because I have many field in my entity

Then have smaller entities. Or, do not update fields individually, but instead have more coarse-grained interactions with the database.

IOW, there is nothing in Room itself that will do what you seek.

UPDATE 2020-09-15: Room now has partial entity support, which can help with this scenario. See this answer for more.