Room Migration- How to add a new NON-NULL and String type column to existing table

Question

I am developing an android application and in my app i have implemented Room Database. My app is already live on playstore as now i am trying to send an update to app where there are changes in schema. I have added new column, its type is string and it should be NOT NULL so i will be providing a default value with it.

I have written a migration query for that, but app always crashes.

Question: Why in expected the modifyDate column notNull=false but i want it to be NOT NULL. I don't see any difference in Expected and Found part expect the notNull status and value

I am unable to find the actual cause of this crash.

Below is my code:

Entity Class

@Keep
@Entity
class PdfFile() {
    //Columns before migration
    @PrimaryKey(autoGenerate = true)
    private var mid = 0
    private var mFile_name: String? = null
    private var mFile_size = "0mb"
    private var mFileDate = "17-06-2020"
    private var mParent_file = ""
    private var mAbsolute_path: String? = null
    private var fileType = ""
    private var isViewed = false
    private var isBookmarked = false

    //TEST MIGRATION
    @ColumnInfo(name = "modifyDate")
    private var modifyDate = ""

    fun setMid(mid: Int) {
        this.mid = mid
    }

    fun getMid(): Int {
        return mid
    }

    fun getMFile_name(): String? {
        return mFile_name
    }

    fun getMFile_size(): String {
        return mFile_size
    }

    fun getMFileDate(): String {
        return mFileDate
    }

    fun getMParent_file(): String {
        return mParent_file
    }

    fun getMAbsolute_path(): String? {
        return mAbsolute_path
    }

    fun getFileType(): String {
        return fileType
    }

    fun getIsViewed(): Boolean {
        return isViewed
    }

    fun getIsBookmarked(): Boolean {
        return isBookmarked
    }

    fun getModifyDate(): String {
        return modifyDate
    }

    fun setMFile_name(name: String) {
        this.mFile_name = name
    }

    fun setMFile_size(size: String) {
        this.mFile_size = size
    }

    fun setMFileDate(date: String) {
        this.mFileDate = date
    }

    fun setMParent_file(parentFile: String) {
        this.mParent_file = parentFile
    }

    fun setMAbsolute_path(path: String) {
        this.mAbsolute_path = path
    }

    fun setFileType(fileType: String) {
        this.fileType = fileType
    }

    fun setIsViewed(isView: Boolean) {
        this.isViewed = isView
    }

    fun setIsBookmarked(isBookmark: Boolean) {
        this.isBookmarked = isBookmark
    }

    fun setModifyDate(date: String) {
        this.modifyDate = date
    }

    override fun equals(obj: Any?): Boolean {
        return if (obj !is PdfFile) {
            false
        } else {
            val PdfFile = obj as PdfFile
            mFile_name == PdfFile.getMFile_name()
                    && mAbsolute_path == PdfFile.getMAbsolute_path()
                    && mFile_size == PdfFile.getMFile_size()
        }
    }
}

Room Database Class

//Please note the previous version was 1 now i have changed to 2 after adding a new column to entity
@Database(
    entities = [PdfFile::class],
    version = 2,
    exportSchema = false
)
abstract class RoomDbData : RoomDatabase() {
    abstract fun taskDao(): DataDao


}

DatabaseManager Class

const val DATABASE_NAME = “MyDb”

class DatabaseManager(context: Context) {

    //Migrating from version 1 to version 2
    val MIGRATION_1_2 = object : Migration(1, 2) {
        override fun migrate(database: SupportSQLiteDatabase) {
            database.execSQL("ALTER TABLE PdfFile ADD COLUMN modifyDate TEXT NOT NULL DEFAULT '' ")
        }
    }

    val appDatabase: RoomDbData

    init {
        appDatabase =
            Room.databaseBuilder(context, RoomDbData::class.java, DATABASE_NAME)
                .allowMainThreadQueries()
                .addMigrations(MIGRATION_1_2)
                .build()
    }


}

EXCEPTION

    Process: mypackagename, PID: 10993
    java.lang.RuntimeException: Exception while computing database live data.
        at androidx.room.RoomTrackingLiveData$1.run(RoomTrackingLiveData.java:92)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
        at java.lang.Thread.run(Thread.java:764)
     Caused by: java.lang.IllegalStateException: Migration didn't properly handle: PdfFile(mypackagename.models.entities.PdfFile).
     Expected:
    TableInfo{name='PdfFile', columns={isBookmarked=Column{name='isBookmarked', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}, modifyDate=Column{name='modifyDate', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, mFile_size=Column{name='mFile_size', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, mid=Column{name='mid', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=1, defaultValue='null'}, mFileDate=Column{name='mFileDate', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, mAbsolute_path=Column{name='mAbsolute_path', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, mParent_file=Column{name='mParent_file', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, mFile_name=Column{name='mFile_name', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, fileType=Column{name='fileType', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, isViewed=Column{name='isViewed', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}}, foreignKeys=[], indices=[]}
     Found:
    TableInfo{name='PdfFile', columns={isBookmarked=Column{name='isBookmarked', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}, modifyDate=Column{name='modifyDate', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0, defaultValue=''''}, mFile_size=Column{name='mFile_size', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, mid=Column{name='mid', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=1, defaultValue='null'}, mFileDate=Column{name='mFileDate', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, mAbsolute_path=Column{name='mAbsolute_path', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, mParent_file=Column{name='mParent_file', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, mFile_name=Column{name='mFile_name', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, fileType=Column{name='fileType', type='TEXT', affinity='2', notNull=false, primaryKeyPosition=0, defaultValue='null'}, isViewed=Column{name='isViewed', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}}, foreignKeys=[], indices=[]}
        at androidx.room.RoomOpenHelper.onUpgrade(RoomOpenHelper.java:103)
        at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.onUpgrade(FrameworkSQLiteOpenHelper.java:124)
        at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:299)
        at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:194)
        at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase(FrameworkSQLiteOpenHelper.java:92)
        at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase(FrameworkSQLiteOpenHelper.java:53)
        at androidx.room.RoomDatabase.inTransaction(RoomDatabase.java:476)
        at androidx.room.RoomDatabase.assertNotSuspendingTransaction(RoomDatabase.java:281)
2020-10-20 15:14:41.031 10993-11039/mypackagename E/AndroidRuntime:     at androidx.room.RoomDatabase.query(RoomDatabase.java:324)
        at androidx.room.util.DBUtil.query(DBUtil.java:83)
        at mypackagename.models.dao.DataDao_Impl$13.call(DataDao_Impl.java:325)
        at mypackagename.models.dao.DataDao_Impl$13.call(DataDao_Impl.java:322)
        at androidx.room.RoomTrackingLiveData$1.run(RoomTrackingLiveData.java:90)
            ... 3 more
2020-10-20 15:14:41.064 1764-1833/? E/InputDispatcher: channel 'f088a5d mypackagename/mypackagename.views.activities.MainActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
2020-10-20 15:14:41.067 1764-1833/? E/InputDispatcher: channel '1aca3d4 mypackagename/mypackagename.views.activities.SplashActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
2020-10-20 15:14:41.110 1764-4588/? E/eglCodecCommon: glUtilsParamSize: unknow param 0x00008cdf
2020-10-20 15:14:41.111 1764-4588/? E/eglCodecCommon: glUtilsParamSize: unknow param 0x00008cdf
2020-10-20 15:14:41.111 1764-4588/? E/eglCodecCommon: glUtilsParamSize: unknow param 0x00008824
2020-10-20 15:14:41.111 1764-4588/? E/eglCodecCommon: glUtilsParamSize: unknow param 0x00008824
2020-10-20 15:14:41.233 1541-4743/? E/AudioFlinger: not enough memory for AudioTrack size=131296
2020-10-20 15:14:41.233 1541-4743/? E/AudioFlinger: createRecordTrack_l() initCheck failed -12; no control block?
2020-10-20 15:14:41.233 2486-7131/? E/AudioRecord: AudioFlinger could not create record track, status: -12
2020-10-20 15:14:41.236 2486-7131/? E/AudioRecord-JNI: Error creating AudioRecord instance: initialization check failed with status -12.
2020-10-20 15:14:41.236 2486-7131/? E/android.media.AudioRecord: Error code -20 when initializing native AudioRecord object.
2020-10-20 15:14:41.237 2486-7131/? E/ActivityThread: Failed to find provider info for 
   

PLEASE NOTE THAT I HAVEN'T MADE ANY CHANGES TO DAO FOR THIS MIGRATION. Is any changed required there too?

Can someone please help me out with this. Any help will be appreciated. Thanks

Answer 1

To make sure modifyDate is non-null you need to make below change:

private var modifyDate = ""

to:

private var modifyDate: String = ""