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/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.room;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* Marks a method in a {@link Dao} annotated class as a raw query method where you can pass the
* query as a {@link androidx.sqlite.db.SupportSQLiteQuery SupportSQLiteQuery}.
*
* {@literal @}Dao
* interface RawDao {
* {@literal @}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 {@link 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, {@code 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.
*
* {@code RawQuery} methods must return a non-void type. If you want to execute a raw query that
* does not return any value, use {@link androidx.room.RoomDatabase#query
* RoomDatabase#query} methods.
*
* RawQuery methods can only be used for read queries. For write queries, use
* {@link androidx.room.RoomDatabase#getOpenHelper
* RoomDatabase.getOpenHelper().getWritableDatabase()}.
*
* Observable Queries:
*
* {@code RawQuery} methods can return observable types but you need to specify which tables are
* accessed in the query using the {@link #observedEntities()} field in the annotation.
*
* {@literal @}Dao
* interface RawDao {
* {@literal @}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 {@link 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;
* }
* }
*
* {@literal @}Dao
* interface RawDao {
* {@literal @}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:
*
* {@code RawQuery} methods can return pojos that include {@link Embedded} fields as well.
*
* public class UserAndPet {
* {@literal @}Embedded
* public User user;
* {@literal @}Embedded
* public Pet pet;
* }
*
* {@literal @}Dao
* interface RawDao {
* {@literal @}RawQuery
* UserAndPet getUserAndPet(SupportSQLiteQuery query);
* }
* UserAndPet received = rawDao.getUserAndPet(
* new SimpleSQLiteQuery("SELECT * FROM User, Pet WHERE User.id = Pet.userId LIMIT 1"))
*
*
* Relations:
*
* {@code RawQuery} return types can also be objects with {@link Relation Relations}.
*
* public class UserAndAllPets {
* {@literal @}Embedded
* public User user;
* {@literal @}Relation(parentColumn = "id", entityColumn = "userId")
* public List<Pet> pets;
* }
*
* {@literal @}Dao
* interface RawDao {
* {@literal @}RawQuery
* List<UserAndAllPets> getUsersAndAllPets(SupportSQLiteQuery query);
* }
* List<UserAndAllPets> result = rawDao.getUsersAndAllPets(
* new SimpleSQLiteQuery("SELECT * FROM users"));
*
*/
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.CLASS)
public @interface RawQuery {
/**
* 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 {@link Entity} or they should reference to
* at least 1 Entity (via {@link Embedded} or {@link Relation}).
*
* Providing this field in a non-observable query has no impact.
*
* {@literal @}Dao
* interface RawDao {
* {@literal @}RawQuery(observedEntities = User.class)
* LiveData<List<User>> getUsers(String query);
* }
* LiveData<List<User>> liveUsers = rawDao.getUsers("select * from User ORDER BY name
* DESC");
*
*
* @return List of entities that should invalidate the query if changed.
*/
Class[] observedEntities() default {};
}