RawQuery

public abstract @interface RawQuery
implements Annotation

android.arch.persistence.room.RawQuery

Marks a method in a Dao annotated class as a raw query method where you can pass the query as a SupportSQLiteQuery. 

 @Dao
 interface RawDao {
     @RawQuery
     User getUserViaQuery(SupportSQLiteQuery query);
 }
 SimpleSQLiteQuery query = new SimpleSQLiteQuery("SELECT * FROM User WHERE id = ? LIMIT 1",
         new Object[]{userId});
 User user2 = rawDao.getUserViaQuery(query);

Room will generate the code based on the return type of the function and failure to pass a proper query will result in a runtime failure or an undefined result.

If you know the query at compile time, you should always prefer Query since it validates the query at compile time and also generates more efficient code since Room can compute the query result at compile time (e.g. it does not need to account for possibly missing columns in the response).

On the other hand, RawQuery serves as an escape hatch where you can build your own SQL query at runtime but still use Room to convert it into objects.

RawQuery methods must return a non-void type. If you want to execute a raw query that does not return any value, use RoomDatabase#query methods.

RawQuery methods can only be used for read queries. For write queries, use RoomDatabase.getOpenHelper().getWritableDatabase().

Observable Queries:

RawQuery methods can return observable types but you need to specify which tables are accessed in the query using the observedEntities() field in the annotation. 

 @Dao
 interface RawDao {
     @RawQuery(observedEntities = User.class)
     LiveData<List<User>> getUsers(SupportSQLiteQuery query);
 }
 LiveData<List<User>> liveUsers = rawDao.getUsers(
     new SimpleSQLiteQuery("SELECT * FROM User ORDER BY name DESC"));
Returning Pojos:

RawQueries can also return plain old java objects, similar to Query methods. 

 public class NameAndLastName {
     public final String name;
     public final String lastName;

     public NameAndLastName(String name, String lastName) {
         this.name = name;
         this.lastName = lastName;
     }
 }

 @Dao
 interface RawDao {
     @RawQuery
     NameAndLastName getNameAndLastName(SupportSQLiteQuery query);
 }
 NameAndLastName result = rawDao.getNameAndLastName(
      new SimpleSQLiteQuery("SELECT * FROM User WHERE id = ?", new Object[]{userId}))
 // or
 NameAndLastName result = rawDao.getNameAndLastName(
      new SimpleSQLiteQuery("SELECT name, lastName FROM User WHERE id = ?",
          new Object[]{userId})))

Pojos with Embedded Fields:

RawQuery methods can return pojos that include Embedded fields as well. 

 public class UserAndPet {
     @Embedded
     public User user;
     @Embedded
     public Pet pet;
 }

 @Dao
 interface RawDao {
     @RawQuery
     UserAndPet getUserAndPet(SupportSQLiteQuery query);
 }
 UserAndPet received = rawDao.getUserAndPet(
         new SimpleSQLiteQuery("SELECT * FROM User, Pet WHERE User.id = Pet.userId LIMIT 1"))
Relations:

RawQuery return types can also be objects with Relations. 

 public class UserAndAllPets {
     @Embedded
     public User user;
     @Relation(parentColumn = "id", entityColumn = "userId")
     public List<Pet> pets;
 }

 @Dao
 interface RawDao {
     @RawQuery
     List<UserAndAllPets> getUsersAndAllPets(SupportSQLiteQuery query);
 }
 List<UserAndAllPets> result = rawDao.getUsersAndAllPets(
      new SimpleSQLiteQuery("SELECT * FROM users"));

Summary

Public methods

Class[] observedEntities()

Denotes the list of entities which are accessed in the provided query and should be observed for invalidation if the query is observable.

Inherited methods

Public methods

observedEntities

Class[] observedEntities ()

Denotes the list of entities which are accessed in the provided query and should be observed for invalidation if the query is observable.

The listed classes should either be annotated with Entity or they should reference to at least 1 Entity (via Embedded or Relation).

Providing this field in a non-observable query has no impact. 

 @Dao
 interface RawDao {
     @RawQuery(observedEntities = User.class)
     LiveData<List<User>> getUsers(String query);
 }
 LiveData<List<User>> liveUsers = rawDao.getUsers("select * from User ORDER BY name
 DESC");

Returns
Class[] List of entities that should invalidate the query if changed.