accum /= i + 1;
    }
    return accum;
  }

  @GwtIncompatible // java.math.BigInteger
  public void testIsPowerOfTwo() {
    for (long x : ALL_LONG_CANDIDATES) {
      // Checks for a single bit set.
      BigInteger bigX = BigInteger.valueOf(x);
      boolean expected = (bigX.signum() > 0) && (bigX.bitCount() == 1);
      assertEquals(expected, LongMath.isPowerOfTwo(x));
    }
  }

  @SuppressWarnings("unchecked")
  public static <K, V> ImmutableBiMap<K, V> of() {
    return (ImmutableBiMap<K, V>) RegularImmutableBiMap.EMPTY;
  }

  /** Returns an immutable bimap containing a single entry. */
  public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1) {
    return new SingletonImmutableBiMap<>(k1, v1);
  }

  /**
   * Returns an immutable map containing the given entries, in order.
   *

Just standard **Python**.

For example, for an `int`:

```Python
item_id: int
```

or for a more complex `Item` model:

```Python
item: Item
```

...and with that single declaration you get:

* Editor support, including:
    * Completion.
    * Type checks.
* Validation of data:
    * Automatic and clear errors when the data is invalid.

首先，确保你创建并激活了[虚拟环境](../virtual-environments.md)，然后安装 `sqlmodel`：

<div class="termy">

```console
$ pip install sqlmodel
---> 100%
```

</div>

## 创建含有单一模型的应用 { #create-the-app-with-a-single-model }

我们先创建应用的最简单的第一个版本，只有一个 **SQLModel** 模型。

稍后我们将通过下面的**多个模型**提高其安全性和多功能性。🤓

### 创建模型 { #create-models }

导入 `SQLModel` 并创建一个数据库模型：

	}

	currentLogger.Trace(tx.Statement.Context, newLogger.BeginAt, func() (string, int64) {
		return newLogger.SQL, tx.RowsAffected
	}, tx.Error)
	tx.Logger = currentLogger
	return
}

// Pluck queries a single column from a model, returning in the slice dest. E.g.:
//
//	var ages []int64
//	db.Model(&users).Pluck("age", &ages)
func (db *DB) Pluck(column string, dest interface{}) (tx *DB) {
	tx = db.getInstance()

		sw.pos += nf
		if sw.pos >= dataEnd && len(sw.sp) > 1 {
			sw.sp = sw.sp[1:] // Ensure last fragment always remains
		}
	}

	// If the last fragment is a hole, then seek to 1-byte before EOF, and
	// read a single byte to ensure the file is the right size.
	if readLastByte && err == nil {
		_, err = mustReadFull(rs, []byte{0})
		sw.pos++
	}

	n = sw.pos - pos0
	switch {
	case err == io.EOF:

			yBytes := Repeat(y, growLen)
			allocs := testing.AllocsPerRun(100, func() {
				buf.Grow(growLen)
				buf.Write(yBytes)
			})
			// Check no allocation occurs in write, as long as we're single-threaded.
			if allocs != 0 {
				t.Errorf("allocation occurred during write")
			}
			// Check that buffer has correct data.
			if !Equal(buf.Bytes()[0:startLen-readBytes], xBytes[readBytes:]) {

      if (newArg == null || Objects.equals(args.get(i), newArg)) {
        if (params.get(i).getType().getRawType().isEnum()) {
          continue; // Nothing better we can do if it's single-value enum
        }
        throw new ParameterHasNoDistinctValueException(params.get(i));
      }
      newArgs.set(i, newArg);
      tester.addEqualityGroup(createInstance(factory, newArgs));

                .collect(Collectors.toMap(
                        upgrade -> upgrade.groupId() + ":" + upgrade.artifactId(), upgrade -> upgrade));
    }

    /**
     * Analyzes the effective model for a single POM to find plugins that need upgrades.
     */
    private Set<String> analyzeEffectiveModelForPlugins(
            UpgradeContext context, Path tempPomPath, Map<String, PluginUpgrade> pluginUpgrades) {

* Added anti-affinity to kube-dns pods. Otherwise the "no single point of failure" setting doesn't actually work (a single node failure can still take down the entire cluster). ([#57683](https://github.com/kubernetes/kubernetes/pull/57683), [@vainu-arto](https://github.com/vainu-arto))

### API-Machinery