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Room database migration for all
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public class DBConstants { | |
// word table | |
public static final String TABLE_WORD = "word_table"; | |
public static final String KEY_WORD = "word"; | |
public static final String KEY_ID = "word_id"; | |
} |
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public class DBUtils { | |
public static ArrayList<String> getColumns(SupportSQLiteDatabase db, String tableName) { | |
ArrayList<String> al = null; | |
Cursor c = null; | |
try { | |
c = db.query("SELECT * FROM " + tableName + " LIMIT 1", null); | |
if (c != null) { | |
al = new ArrayList<>(Arrays.asList(c.getColumnNames())); | |
} | |
} catch (Exception e) { | |
e.printStackTrace(); | |
} finally { | |
if (c != null) | |
c.close(); | |
} | |
return al; | |
} | |
} |
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@Entity(tableName = DBConstants.TABLE_WORD) | |
public class Word { | |
public static void upgradeWordTable(SupportSQLiteDatabase database) { | |
ArrayList<String> columns = DBUtils.getColumns(database, DBConstants.TABLE_WORD); | |
// 1. Create new table | |
final String TABLE_NAME_TEMP = "_temp" + DBConstants.TABLE_WORD; | |
database.execSQL("CREATE TABLE IF NOT EXISTS `" + TABLE_NAME_TEMP + "` (`" + DBConstants.KEY_WORD + "` TEXT NOT NULL, `" + DBConstants.KEY_ID + "` TEXT, PRIMARY KEY(`" + DBConstants.KEY_WORD + "`))"); | |
// 2. find common columns. | |
columns.retainAll(DBUtils.getColumns(database, TABLE_NAME_TEMP)); | |
final String COLS = TextUtils.join(",", columns); | |
// 3. Copy the data | |
database.execSQL("INSERT INTO " + TABLE_NAME_TEMP + " (" + COLS + ") " | |
+ "SELECT " + COLS + " " | |
+ "FROM " + DBConstants.TABLE_WORD); | |
// 4. Remove the old table | |
database.execSQL("DROP TABLE " + DBConstants.TABLE_WORD); | |
// 5. Change the table name to the correct one | |
database.execSQL("ALTER TABLE " + TABLE_NAME_TEMP + " RENAME TO " + DBConstants.TABLE_WORD); | |
} | |
@PrimaryKey | |
@NonNull | |
@ColumnInfo(name = DBConstants.KEY_WORD) | |
private String mWord; | |
@Nullable | |
@ColumnInfo(name = DBConstants.KEY_ID) | |
private String mId; | |
public Word(@NonNull String word, @Nullable String mId) { | |
this.mWord = word; | |
this.mId = mId; | |
} | |
public String getWord() { | |
return this.mWord; | |
} | |
@NonNull | |
public String getId() { | |
return mId == null ? "" : mId; | |
} | |
} |
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@Database(entities = {Word.class}, version = 2) | |
public abstract class WordRoomDatabase extends RoomDatabase { | |
public abstract WordDao wordDao(); | |
private static WordRoomDatabase INSTANCE; | |
static WordRoomDatabase getDatabase(final Context context) { | |
if (INSTANCE == null) { | |
synchronized (WordRoomDatabase.class) { | |
if (INSTANCE == null) { | |
INSTANCE = Room.databaseBuilder(context.getApplicationContext(), | |
WordRoomDatabase.class, "word_database") | |
.addMigrations(WordRoomDatabase.MIGRATION_1_2) | |
.build(); | |
} | |
} | |
} | |
return INSTANCE; | |
} | |
private static final Migration MIGRATION_1_2 = new Migration(1, 2) { | |
@Override | |
public void migrate(@NonNull SupportSQLiteDatabase database) { | |
Word.upgradeWordTable(database); | |
} | |
}; | |
} |
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