}
		switch tgtStatus {
		case replication.Pending:
			tgtSizeS.pendingCount++
			tgtSizeS.pendingSize += oi.Size
			sizeS.pendingCount++
			sizeS.pendingSize += oi.Size
		case replication.Failed:
			tgtSizeS.failedSize += oi.Size
			tgtSizeS.failedCount++
			sizeS.failedSize += oi.Size
			sizeS.failedCount++
		case replication.Completed, replication.CompletedLegacy:

  }

  private static <E> ImmutableList<E> copyFromCollection(Collection<? extends E> collection) {
    Object[] elements = collection.toArray();
    switch (elements.length) {
      case 0:
        return of();
      case 1:
        @SuppressWarnings("unchecked") // safe because it came from `collection`
        E element = (E) elements[0];
        return of(element);
      default:

 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Objects;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.Collection;
import java.util.Iterator;
import java.util.Set;
import javax.annotation.CheckForNull;

{!../../docs_src/sql_databases/sql_app/database.py!}
```

### 创建一个`Base`类

现在我们将使用`declarative_base()`返回一个类。

稍后我们将继承这个类，来创建每个数据库模型或类（ORM 模型）：

```Python hl_lines="13"
{!../../docs_src/sql_databases/sql_app/database.py!}
```

## 创建数据库模型

现在让我们看看文件`sql_app/models.py`。

### 用`Base`类来创建 SQLAlchemy 模型

我们将使用我们之前创建的`Base`类来创建 SQLAlchemy 模型。

/// tip

The available features and the components that comprise each feature are as follows:

| Feature | Components |
|---------|------------|
CRDs, and other cluster wide configs | Base
Traffic Management | Pilot
Security | Pilot
Configuration management | Pilot
AutoInjection | Pilot
Gateways | Ingress gateway
Gateways | Egress gateway
Policy | Policy (deprecated)

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.collect.Ordering.ArbitraryOrdering;
import com.google.common.collect.Ordering.IncomparableValueException;
import com.google.common.collect.testing.Helpers;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.collect.Ordering.ArbitraryOrdering;
import com.google.common.collect.Ordering.IncomparableValueException;
import com.google.common.collect.testing.Helpers;

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;

import static com.google.common.truth.Truth.assertThat;
import static java.util.concurrent.TimeUnit.DAYS;
import static java.util.concurrent.TimeUnit.SECONDS;
import static org.junit.Assert.assertThrows;

import com.google.common.base.Function;
import com.google.common.cache.CacheBuilderFactory.DurationSpec;
import com.google.common.cache.LocalCache.Strength;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.io;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.io.TestOption.AVAILABLE_ALWAYS_ZERO;
import static com.google.common.io.TestOption.CLOSE_THROWS;
import static com.google.common.io.TestOption.OPEN_THROWS;