RoomModule.java

Room.databaseBuilder(...)
.addMigrations(new Migration(3, 4) {
  @Override public void migrate(@NonNull SupportSQLiteDatabase database) {
    database.execSQL("CREATE VIRTUAL TABLE IF NOT EXISTS `entriesFts` USING FTS4(`primary_kanji`, `primary_reading`, `other_kanji`, `other_readings`, content=`entries`)");
    database.execSQL("INSERT INTO entriesFts(entriesFts) VALUES ('rebuild')");
  }
})
.build();