我正在迁移我的 Room 数据库。我想添加新表。所以我创建了这样的 Entry 类:

@Entity(foreignKeys = {@ForeignKey(entity = Project.class,
    parentColumns = "projectId",
    childColumns = "projectId",
    onDelete = ForeignKey.CASCADE)},
    indices = {
            @Index(name = "projectId_index", value = {"projectId"})
    })
public class ProjectDimension {
    @PrimaryKey(autoGenerate = true)
    private long dimensionId;

    @ColumnInfo
    private long projectId;

    @ColumnInfo
    private String name;

    @ColumnInfo
    private String value;

    // getters and setters here...
}

那么我的道是这样的:

@Dao
public interface ProjectDimensionDao {

    @Query("SELECT * FROM ProjectDimension")
    Single<List<ProjectDimension>> getAll();

    @Query("SELECT * FROM ProjectDimension WHERE projectId = :projectId")
    Single<List<ProjectDimension>> getByProject(long projectId);

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    long insert(ProjectDimension projectDimension);

    @Delete
    void delete(ProjectDimension projectDimension);
}

最后是我的数据库类:

@Database(entities = {
    Contact.class,
    ContactEmail.class,
    ContactPhone.class,
    Monitoring.class,
    Organization.class,
    OrgEmail.class,
    OrgPhone.class,
    Project.class,
    ProjectContact.class,
    ProjectLocation.class,
    ProjectDimension.class
}, version = 2)
public abstract class MonitoringDatabase extends RoomDatabase {

    private static MonitoringDatabase instance;

    // other Data Access Objects (DAO) here...
    public abstract ProjectDimensionDao projectDimensionDao();

    public static MonitoringDatabase getInstance(Context context) {
        if (instance == null) {
            instance = Room.databaseBuilder(context.getApplicationContext(),
                    MonitoringDatabase.class, "monitoring-database")
                        .addMigrations(MIGRATION_1_2)
                        .build();
        }
        return instance;
    }

    /**
     * Upgrade database from version 1 to 2.
     * Details: Added new table named ProjectDimension
     */
    private static final Migration MIGRATION_1_2 = new Migration(1, 2) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            // create ProjectDimension table
            database.execSQL("CREATE TABLE `ProjectDimension` (`dimensionId` INTEGER, `projectId` INTEGER, " +
                    "`name` TEXT, `value` TEXT, " +
                    "PRIMARY KEY(`dimensionId`), " +
                    "FOREIGN KEY(`projectId`) REFERENCES `Project`(`projectId`) ON DELETE CASCADE)");
        }
    };

    public static void destroyInstance() {
        instance = null;
    }
}

运行后，出现如下错误:

Expected:
TableInfo{name='ProjectDimension', columns={name=Column{name='name', type='TEXT', notNull=false, primaryKeyPosition=0}, value=Column{name='value', type='TEXT', notNull=false, primaryKeyPosition=0}, projectId=Column{name='projectId', type='INTEGER', notNull=true, primaryKeyPosition=0}, dimensionId=Column{name='dimensionId', type='INTEGER', notNull=true, primaryKeyPosition=1}}, foreignKeys=[ForeignKey{referenceTable='Project', onDelete='CASCADE', onUpdate='NO ACTION', columnNames=[projectId], referenceColumnNames=[projectId]}], indices=[Index{name='projectId_index', unique=false, columns=[projectId]}]}

Found:
TableInfo{name='ProjectDimension', columns={name=Column{name='name', type='TEXT', notNull=false, primaryKeyPosition=0}, value=Column{name='value', type='TEXT', notNull=false, primaryKeyPosition=0}, projectId=Column{name='projectId', type='INTEGER', notNull=false, primaryKeyPosition=0}, dimensionId=Column{name='dimensionId', type='INTEGER', notNull=false, primaryKeyPosition=1}}, foreignKeys=[ForeignKey{referenceTable='Project', onDelete='CASCADE', onUpdate='NO ACTION', columnNames=[projectId], referenceColumnNames=[projectId]}], indices=null}

我认为问题出在我的 CREATE 语句中。我一直在为此寻找合适的 SQL 查询，但仍然找不到。有人帮忙!

最佳答案

您有 2 个错误，一个关于 NOT NULL 列属性，另一个关于外键。

区别如下:

预期:

projectId notNull=true

dimensionId notNull=true

foreignKeys indices=[Index{name='projectId_index', unique=false, columns=[projectId]}]}

找到

projectId notNull=false

dimensionId notNull=false

foreignKeys indices=null

我可以帮助解决第一个问题，在您的实体中，long 类型不能为空。将其更改为 Long 以使其工作。

对于第二个，将类似的内容添加到您的迁移函数中

database.execSQL("CREATE INDEX projectId_index ON Project (projectId)");

关于java - 房间用索引创建表，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/49419520/