带索引实体的房间数据库迁移

Question

我有 'ImagePendingDBStore' 个实体，我在这个实体中又添加了 4 列（请参阅下面代码中的注释）。在此，一列被索引 'referenceId'

@Entity(tableName = "ImagePendingDBStore",indices = {@Index(value = "referenceId")})
public class ImagePendingDBStore {

 @PrimaryKey(autoGenerate = true)
 @NonNull
 private int ImageId;
 private String referenceId;
 private Date createdAt;
 private Date updatedAt;
 private String imageAbsolutePath;
 private int synced = 0;
 private String customerFirstName;
 private String customerMiddleName;
 private String customerLastName;
 private String dasId;
 private String documentName;
 private String imageIdRandom;
 private int imageResolution;

 //new columns
 private String dealerId;
 private String lat;
 private String lng;
 private Date imageCaptureDate;
}

我在数据库class中的迁移逻辑如下：

public static final Migration MIGRATION_1_2 = new Migration(1, 2) {
    @Override
    public void migrate(SupportSQLiteDatabase database) {
        database.execSQL("ALTER TABLE ImagePendingDBStore ADD COLUMN dealerId TEXT");
        database.execSQL("ALTER TABLE ImagePendingDBStore ADD COLUMN lat TEXT");
        database.execSQL("ALTER TABLE ImagePendingDBStore ADD COLUMN lng TEXT");
        database.execSQL("ALTER TABLE ImagePendingDBStore ADD COLUMN imageCaptureDate DATE");
        database.execSQL("CREATE  INDEX index_ImagePendingDBStore_referenceId ON ImagePendingDBStore (referenceId)");
    }
};

以下是我面临的错误：

Caused by: android.database.sqlite.SQLiteException: index index_ImagePendingDBStore_referenceId already exists (code 1): , while compiling: CREATE INDEX index_ImagePendingDBStore_referenceId ON ImagePendingDBStore (referenceId)
    #################################################################
    Error Code : 1 (SQLITE_ERROR)
    Caused By : SQL(query) error or missing database.
        (index index_ImagePendingDBStore_referenceId already exists (code 1): , while compiling: CREATE INDEX index_ImagePendingDBStore_referenceId ON ImagePendingDBStore (referenceId))
    #################################################################

Answer 1

正如消息所说 index_ImagePendingDBStore_referenceId 已经存在。

您只需要 4 个 ALTER 语句，因为索引存在，即您没有添加它。因为它已经存在，所以添加 4 列不需要更改索引。

您可以删除该行：-

database.execSQL("CREATE  INDEX index_ImagePendingDBStore_referenceId ON ImagePendingDBStore (referenceId)");