The document describes the use of the Room library in Android for managing databases through an ORM abstraction layer, with examples provided in Kotlin. It covers the structure of entities, DAOs, and their respective queries for CRUD operations on a products database, including foreign keys, nested objects, and specific queries to filter and manage data. The document serves as a guide for developers implementing Room in their Android applications.

1. Database handling
with
Room
CC4.0 Kathleen Cole

2. About me
Sergi Martínez
@sergiandreplace
Android GDE & dev at Schibsted Spain

3. Disclaimer:
All examples are
in Kotlin

4. What is Room?

5. A library to handle android
databases via an abstraction
layer

6. Tl,dr;
An ORM

7. Components

8. Entity
A class representing a
database row

9. DAO
An interface defining
how to access to db

10. Database
Holds definition for
DAOs and Entities

11. Before anything else
repositories {
jcenter()
maven { url 'https://maven.google.com' }
}
def room = '1.0.0-beta2'
implementation "android.arch.persistence.room:runtime:${room}"
kapt "android.arch.persistence.room:compiler:${room}"

12. Entities

13. Simple entity
@Entity(tableName = "products")
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@ColumnInfo(name = "qty") var quantity: Long
)

14. Simple entity
@Entity(tableName = "products")
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@ColumnInfo(name = "qty") var quantity: Long
)

15. Simple entity
@Entity(tableName = "products")
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@ColumnInfo(name = "qty") var quantity: Long
)

16. Simple entity
@Entity(tableName = "products")
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@ColumnInfo(name = "qty") var quantity: Long
)

17. Indexes
@Entity(tableName = "inventory",
indices = arrayOf(Index("provider_id", "product_id", unique = true)))
class InventoryEntity(
@PrimaryKey() var id: Long,
@ColumnInfo(name = "provider_id") var providerId: Long,
@ColumnInfo(name = "product_id") var productId: Long,
@ColumnInfo(name = "qty") var quantity: Long
)

18. Composed PK
@Entity(tableName = "inventory",
primaryKeys = arrayOf("provider_id", "product_id"))
class InventoryEntity(
@ColumnInfo(name = "provider_id") var providerId: Long,
@ColumnInfo(name = "product_id") var productId: Long,
@ColumnInfo(name = "qty") var quantity: Long
)

19. Foreign keys
@Entity(
tableName = "inventory",
foreignKeys = arrayOf(
ForeignKey(
entity = ProductEntity::class,
parentColumns = arrayOf("id"),
childColumns = arrayOf("product_id")
)
)
)
class InventoryEntity(
@PrimaryKey() var id: Long,
@ColumnInfo(name = "provider_id") var providerId: Long,
@ColumnInfo(name = "product_id") var productId: Long,
@ColumnInfo(name = "qty") var quantity: Long
)

20. Foreign keys
@Entity(
tableName = "inventory",
foreignKeys = arrayOf(
ForeignKey(
entity = ProductEntity::class,
parentColumns = arrayOf("id"),
childColumns = arrayOf("product_id")
)
)
)
class InventoryEntity(
@PrimaryKey() var id: Long,
@ColumnInfo(name = "provider_id") var providerId: Long,
@ColumnInfo(name = "product_id") var productId: Long,
@ColumnInfo(name = "qty") var quantity: Long
)

21. Foreign keys
@Entity(
tableName = "inventory",
foreignKeys = arrayOf(
ForeignKey(
entity = ProductEntity::class,
parentColumns = arrayOf("id"),
childColumns = arrayOf("product_id")
)
)
)
class InventoryEntity(
@PrimaryKey() var id: Long,
@ColumnInfo(name = "provider_id") var providerId: Long,
@ColumnInfo(name = "product_id") var productId: Long,
@ColumnInfo(name = "qty") var quantity: Long
)

22. Foreign keys
@Entity(
tableName = "inventory",
foreignKeys = arrayOf(
ForeignKey(
entity = ProductEntity::class,
parentColumns = arrayOf("id"),
childColumns = arrayOf("product_id")
)
)
)
class InventoryEntity(
@PrimaryKey() var id: Long,
@ColumnInfo(name = "provider_id") var providerId: Long,
@ColumnInfo(name = "product_id") var productId: Long,
@ColumnInfo(name = "qty") var quantity: Long
)

23. Foreign keys
@Entity(
tableName = "inventory",
foreignKeys = arrayOf(
ForeignKey(
entity = ProductEntity::class,
parentColumns = arrayOf("id"),
childColumns = arrayOf("product_id")
)
)
)
class InventoryEntity(
@PrimaryKey() var id: Long,
@ColumnInfo(name = "provider_id") var providerId: Long,
@ColumnInfo(name = "product_id") var productId: Long,
@ColumnInfo(name = "qty") var quantity: Long
)

24. Foreign keys
@Entity(
tableName = "inventory",
foreignKeys = arrayOf(
ForeignKey(
entity = ProductEntity::class,
parentColumns = arrayOf("id"),
childColumns = arrayOf("product_id")
)
)
)
class InventoryEntity(
@PrimaryKey() var id: Long,
@ColumnInfo(name = "provider_id") var providerId: Long,
@ColumnInfo(name = "product_id") var productId: Long,
@ColumnInfo(name = "qty") var quantity: Long
)

25. Nested objects
@Entity(tableName = "products")
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@Embedded var info: ProductInfo
)
class ProductInfo(
@ColumnInfo(name = "color") var color: String,
@ColumnInfo(name = "size") var size: String
)
products
id name description color size

26. Nested objects
@Entity(tableName = "products")
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@Embedded var info: ProductInfo
)
class ProductInfo(
@ColumnInfo(name = "color") var color: String,
@ColumnInfo(name = "size") var size: String
)
products
id name description color size

27. Nested objects
@Entity(tableName = "products")
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@Embedded var info: ProductInfo
)
class ProductInfo(
@ColumnInfo(name = "color") var color: String,
@ColumnInfo(name = "size") var size: String
)
products
id name description color size

28. Nested objects
@Entity(tableName = "products")
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@Embedded var info: ProductInfo
)
class ProductInfo(
@ColumnInfo(name = "color") var color: String,
@ColumnInfo(name = "size") var size: String
)
products
id name description color size

29. DAOs

30. Simple DAO
@Dao
interface ProductsDao {
@Insert(onConflict = REPLACE)
fun insert(productEntity: ProductEntity): Long
@Query("Select * from products")
fun getAll(): List<ProductEntity>
@Update
fun update(productEntity: ProductEntity): Int
@Delete
fun delete(productEntity: ProductEntity): Int
}

31. Simple DAO
@Dao
interface ProductsDao {
@Insert(onConflict = REPLACE)
fun insert(productEntity: ProductEntity): Long
@Query("Select * from products")
fun getAll(): List<ProductEntity>
@Update
fun update(productEntity: ProductEntity): Int
@Delete
fun delete(productEntity: ProductEntity): Int
}

32. Simple DAO
@Dao
interface ProductsDao {
@Insert(onConflict = REPLACE)
fun insert(productEntity: ProductEntity): Long
@Query("Select * from products")
fun getAll(): List<ProductEntity>
@Update
fun update(productEntity: ProductEntity): Int
@Delete
fun delete(productEntity: ProductEntity): Int
}
Row id

33. Simple DAO
@Dao
interface ProductsDao {
@Insert(onConflict = REPLACE)
fun insert(productEntity: ProductEntity): Long
@Query("Select * from products")
fun getAll(): List<ProductEntity>
@Update
fun update(productEntity: ProductEntity): Int
@Delete
fun delete(productEntity: ProductEntity): Int
}

34. Simple DAO
@Dao
interface ProductsDao {
@Insert(onConflict = REPLACE)
fun insert(productEntity: ProductEntity): Long
@Query("Select * from products")
fun getAll(): List<ProductEntity>
@Update
fun update(productEntity: ProductEntity): Int
@Delete
fun delete(productEntity: ProductEntity): Int
}
# Modified rows

35. Simple DAO
@Dao
interface ProductsDao {
@Insert(onConflict = REPLACE)
fun insert(productEntity: ProductEntity): Long
@Query("Select * from products")
fun getAll(): List<ProductEntity>
@Update
fun update(productEntity: ProductEntity): Int
@Delete
fun delete(productEntity: ProductEntity): Int
}

36. Insert
@Dao
interface ProductsDao {
@Insert(onConflict = REPLACE)
fun insert(product: ProductEntity): Long
@Insert(onConflict = REPLACE)
fun insertAll(vararg products: ProductEntity) : List<Long>
@Insert(onConflict = ROLLBACK)
fun insertTwo(product: ProductEntity, otherProduct: ProductEntity): List<Long>
@Insert(onConflict = ABORT)
fun weirdInsert(product: ProductEntity, products: List<ProductEntity>): List<Long>
}

37. Update
@Dao
interface ProductsDao {
@Update()
fun update(product: ProductEntity): Int
@Update()
fun update(vararg users: ProductEntity): Int
}

38. Delete
@Dao
interface ProductsDao {
@Delete()
fun delete(product: ProductEntity): Int
@Delete()
fun delete(vararg users: ProductEntity): Int
}
Only primary key is matched

39. Query
@Dao
interface ProductsDao {
@Query("Select * from products")
fun getAllAsList(): List<ProductEntity>
@Query("SELECT * FROM products")
fun getAllAsArray(): Array<ProductEntity>
@Query("SELECT * FROM products WHERE name = :name")
fun getProductsWithName(name: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name like :name OR description like :name")
fun searchProduct(term: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name in (:names)")
fun getProductsByName(names: List<String>): List<ProductEntity>
@Query("SELECT * FROM products WHERE qty >= :minQty AND qty <= :maxQty")
fun getProductsWithinInventory(minQty: Int, maxQty: Int): List<ProductEntity>
}

40. Query
@Dao
interface ProductsDao {
@Query("Select * from products")
fun getAllAsList(): List<ProductEntity>
@Query("SELECT * FROM products")
fun getAllAsArray(): Array<ProductEntity>
@Query("SELECT * FROM products WHERE name = :name")
fun getProductsWithName(name: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name like :name OR description like :name")
fun searchProduct(term: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name in (:names)")
fun getProductsByName(names: List<String>): List<ProductEntity>
@Query("SELECT * FROM products WHERE qty >= :minQty AND qty <= :maxQty")
fun getProductsWithinInventory(minQty: Int, maxQty: Int): List<ProductEntity>
}

41. Query
@Dao
interface ProductsDao {
@Query("Select * from products")
fun getAllAsList(): List<ProductEntity>
@Query("SELECT * FROM products")
fun getAllAsArray(): Array<ProductEntity>
@Query("SELECT * FROM products WHERE name = :name")
fun getProductsWithName(name: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name like :name OR description like :name")
fun searchProduct(term: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name in (:names)")
fun getProductsByName(names: List<String>): List<ProductEntity>
@Query("SELECT * FROM products WHERE qty >= :minQty AND qty <= :maxQty")
fun getProductsWithinInventory(minQty: Int, maxQty: Int): List<ProductEntity>
}

42. Query
@Dao
interface ProductsDao {
@Query("Select * from products")
fun getAllAsList(): List<ProductEntity>
@Query("SELECT * FROM products")
fun getAllAsArray(): Array<ProductEntity>
@Query("SELECT * FROM products WHERE name = :name")
fun getProductsWithName(name: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name like :name OR description like :name")
fun searchProduct(term: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name in (:names)")
fun getProductsByName(names: List<String>): List<ProductEntity>
@Query("SELECT * FROM products WHERE qty >= :minQty AND qty <= :maxQty")
fun getProductsWithinInventory(minQty: Int, maxQty: Int): List<ProductEntity>
}

43. Query
@Dao
interface ProductsDao {
@Query("Select * from products")
fun getAllAsList(): List<ProductEntity>
@Query("SELECT * FROM products")
fun getAllAsArray(): Array<ProductEntity>
@Query("SELECT * FROM products WHERE name = :name")
fun getProductsWithName(name: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name like :name OR description like :name")
fun searchProduct(term: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name in (:names)")
fun getProductsByName(names: List<String>): List<ProductEntity>
@Query("SELECT * FROM products WHERE qty >= :minQty AND qty <= :maxQty")
fun getProductsWithinInventory(minQty: Int, maxQty: Int): List<ProductEntity>
}

44. Query
@Dao
interface ProductsDao {
@Query("Select * from products")
fun getAllAsList(): List<ProductEntity>
@Query("SELECT * FROM products")
fun getAllAsArray(): Array<ProductEntity>
@Query("SELECT * FROM products WHERE name = :name")
fun getProductsWithName(name: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name like :name OR description like :name")
fun searchProduct(term: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name in (:names)")
fun getProductsByName(names: List<String>): List<ProductEntity>
@Query("SELECT * FROM products WHERE qty >= :minQty AND qty <= :maxQty")
fun getProductsWithinInventory(minQty: Int, maxQty: Int): List<ProductEntity>
}

45. Query
@Dao
interface ProductsDao {
@Query("Select * from products")
fun getAllAsList(): List<ProductEntity>
@Query("SELECT * FROM products")
fun getAllAsArray(): Array<ProductEntity>
@Query("SELECT * FROM products WHERE name = :name")
fun getProductsWithName(name: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name like :name OR description like :name")
fun searchProduct(term: String): List<ProductEntity>
@Query("SELECT * FROM products WHERE name in (:names)")
fun getProductsByName(names: List<String>): List<ProductEntity>
@Query("SELECT * FROM products WHERE qty >= :minQty AND qty <= :maxQty")
fun getProductsWithinInventory(minQty: Int, maxQty: Int): List<ProductEntity>
}

46. Query
@Dao
interface ProductsDao {
@Query("SELECT * FROM products WHERE id = :id")
fun getProducts(id: Long): ProductEntity
@Query("SELECT COUNT(*) FROM products")
fun getProductsCount(): Int
@Query("SELECT COUNT(*) AS count, name FROM products GROUP BY name")
fun getProductsCountByName(): List<ProductCountEntity>
}
class ProductCountEntity(
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "count") var count: Int
)

47. Query
@Dao
interface ProductsDao {
@Query("SELECT * FROM products WHERE id = :id")
fun getProducts(id: Long): ProductEntity
@Query("SELECT COUNT(*) FROM products")
fun getProductsCount(): Int
@Query("SELECT COUNT(*) AS count, name FROM products GROUP BY name")
fun getProductsCountByName(): List<ProductCountEntity>
}
class ProductCountEntity(
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "count") var count: Int
)

48. Query
@Dao
interface ProductsDao {
@Query("SELECT * FROM products WHERE id = :id")
fun getProducts(id: Long): ProductEntity
@Query("SELECT COUNT(*) FROM products")
fun getProductsCount(): Int
@Query("SELECT COUNT(*) AS count, name FROM products GROUP BY name")
fun getProductsCountByName(): List<ProductCountEntity>
}
class ProductCountEntity(
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "count") var count: Int
)

49. Query
@Dao
interface ProductsDao {
@Query("SELECT * FROM products WHERE id = :id")
fun getProducts(id: Long): ProductEntity
@Query("SELECT COUNT(*) FROM products")
fun getProductsCount(): Int
@Query("SELECT COUNT(*) AS count, name FROM products GROUP BY name")
fun getProductsCountByName(): List<ProductCountEntity>
}
class ProductCountEntity(
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "count") var count: Int
)

50. Database

51. Database
@Database(
entities = arrayOf(
ProductEntity::class,
InventoryEntity::class
),
version = 1
)
abstract class MyDatabase : RoomDatabase() {
abstract fun productsDao(): ProductsDao
abstract fun inventoryDao(): InventoryDao
}

52. Database
@Database(
entities = arrayOf(
ProductEntity::class,
InventoryEntity::class
),
version = 1
)
abstract class MyDatabase : RoomDatabase() {
abstract fun productsDao(): ProductsDao
abstract fun inventoryDao(): InventoryDao
}

53. Database
@Database(
entities = arrayOf(
ProductEntity::class,
InventoryEntity::class
),
version = 1
)
abstract class MyDatabase : RoomDatabase() {
abstract fun productsDao(): ProductsDao
abstract fun inventoryDao(): InventoryDao
}

54. Database
@Database(
entities = arrayOf(
ProductEntity::class,
InventoryEntity::class
),
version = 1
)
abstract class MyDatabase : RoomDatabase() {
abstract fun productsDao(): ProductsDao
abstract fun inventoryDao(): InventoryDao
}

55. Using database
val database: MyDatabase = Room
.databaseBuilder(applicationContext, MyDatabase::class.java, "database")
.build()
val products = database.productsDao().getAllAsList()

56. Using database
val database: MyDatabase = Room
.databaseBuilder(applicationContext, MyDatabase::class.java, "database")
.build()
val products = database.productsDao().getAllAsList()

57. Using database
val database: MyDatabase = Room
.databaseBuilder(applicationContext, MyDatabase::class.java, "database")
.build()
val products = database.productsDao().getAllAsList()

58. Use a single instance of
database!

59. Type Converters

60. Date (Boo)
vs.
Three-ten-abp (Yaay!)

61. Type converters
class DateTimeConverter {
private val df : DateTimeFormatter = DateTimeFormatter.ISO_LOCAL_DATE_TIME
@TypeConverter
fun toTimestamp(dateTime: LocalDateTime) : String {
return dateTime.format(df)
}
@TypeConverter
fun toDateTime(timestamp:String) : LocalDateTime {
return LocalDateTime.parse(timestamp, df);
}
}

62. Type converters
class DateTimeConverter {
private val df : DateTimeFormatter = DateTimeFormatter.ISO_LOCAL_DATE_TIME
@TypeConverter
fun toTimestamp(dateTime: LocalDateTime) : String {
return dateTime.format(df)
}
@TypeConverter
fun toDateTime(timestamp:String) : LocalDateTime {
return LocalDateTime.parse(timestamp, df);
}
}

63. Type converters
@Database(entities = arrayOf(ProductEntity::class), version = 1)
@TypeConverters(DateTimeConverter::class)
abstract class MyDatabase : RoomDatabase() {
abstract fun productsDao(): ProductsDao
}

64. Type converters
@Dao
@TypeConverters(DateTimeConverter::class)
interface InventoryDao {
@Query("Select * from inventory where date = :date")
fun getByDate(date: LocalDateTime)
@Query("Select * from inventory where date = :date")
fun getByDate2(date: LocalDateTime)
}

65. Type converters
@Dao
interface InventoryDao {
@Query("Select * from inventory where date = :date")
@TypeConverters(DateTimeConverter::class)
fun getByDate(date: LocalDateTime)
@Query("Select * from inventory where date = :date")
fun getByDate2(date: LocalDateTime)
}

66. Type converters
@Dao
interface InventoryDao {
@Query("Select * from inventory where date = :date")
fun getByDate(date: LocalDateTime)
@Query("Select * from inventory where date = :date")
fun getByDate2(@TypeConverters(DateTimeConverter::class) date: LocalDateTime)
}

67. Type converters
@Entity(tableName = "products")
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@ColumnInfo(name = "qty") var quantity: Long,
@ColumnInfo(name = "purchase_date") var purchaseDate: LocalDateTime
)

68. Type converters
@Entity(tableName = "products")
@TypeConverters(DateTimeConverter::class)
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@ColumnInfo(name = "qty") var quantity: Long,
@ColumnInfo(name = "purchase_date") var purchaseDate: LocalDateTime
)

69. Type converters
@Entity(tableName = "products")
class ProductEntity(
@PrimaryKey() @ColumnInfo(name = "id") var id: Long,
@ColumnInfo(name = "name") var name: String,
@ColumnInfo(name = "description") var description: String,
@ColumnInfo(name = "qty") var quantity: Long,
@TypeConverters(DateTimeConverter::class)
@ColumnInfo(name = "purchase_date") var purchaseDate: LocalDateTime
)

70. Migrations
val migrationFrom1To2 = object : Migration(1, 2) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("ALTER TABLE products ADD COLUMN prices INTEGER")
}
}
val migrationFrom2To3 = object : Migration(2, 3) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("ALTER TABLE products ADD COLUMN color TEXT")
}
}
val database: MyDatabase = Room
.databaseBuilder(applicationContext, MyDatabase::class.java, "database")
.addMigrations(migrationFrom1To2, migrationFrom2To3)
.build()

71. Migrations
val migrationFrom1To2 = object : Migration(1, 2) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("ALTER TABLE products ADD COLUMN prices INTEGER")
}
}
val migrationFrom2To3 = object : Migration(2, 3) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("ALTER TABLE products ADD COLUMN color TEXT")
}
}
val database: MyDatabase = Room
.databaseBuilder(applicationContext, MyDatabase::class.java, "database")
.addMigrations(migrationFrom1To2, migrationFrom2To3)
.build()

72. Migrations
val migrationFrom1To2 = object : Migration(1, 2) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("ALTER TABLE products ADD COLUMN prices INTEGER")
}
}
val migrationFrom2To3 = object : Migration(2, 3) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("ALTER TABLE products ADD COLUMN color TEXT")
}
}
val database: MyDatabase = Room
.databaseBuilder(applicationContext, MyDatabase::class.java, "database")
.addMigrations(migrationFrom1To2, migrationFrom2To3)
.build()

73. Migrations
val migrationFrom1To2 = object : Migration(1, 2) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("ALTER TABLE products ADD COLUMN prices INTEGER")
}
}
val migrationFrom2To3 = object : Migration(2, 3) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("ALTER TABLE products ADD COLUMN color TEXT")
}
}
val database: MyDatabase = Room
.databaseBuilder(applicationContext, MyDatabase::class.java, "database")
.addMigrations(migrationFrom1To2, migrationFrom2To3)
.build()

74. Migrations
@Database(entities = arrayOf(ProductEntity::class), version = 3)
@TypeConverters(DateTimeConverter::class)
abstract class MyDatabase : RoomDatabase() {
abstract fun productsDao(): ProductsDao
}

75. Warning!
If no migration is provided,
Room will rebuilt database
based on schema

76. LiveData
@Query("Select * from products")
fun getAllAsList(): LiveData<List<ProductEntity>>

77. RxJava 2
def room = '1.0.0-beta2'
implementation "android.arch.persistence.room:runtime:${room}"
kapt "android.arch.persistence.room:compiler:${room}"
implementation "android.arch.persistence.room:rxjava2:${room}"

78. RxJava 2
@Query("Select * from products")
fun getAllAsList(): Flowable<List<ProductEntity>>
@Query("SELECT * FROM products WHERE id = :id")
fun getProductById(id: Long): Single<ProductEntity>
@Query("SELECT * FROM products WHERE name = :name")
fun getProductByName(name: String): Maybe<ProductEntity>

79. RxJava 2
Flowable Maybe Single
No data - Just onComplete onError
Data onNext onSuccess onSuccess
Update onNext - -

80. Moar things!

81. But enough for today

82. Questions?