驱动实例是否存在
@param string $alias
@return bool
322652
public static function instanceExists($alias = null)
	{
		if('' === static::$driverName)
		{
			static::init();
		}
		return isset(self::$instances[static::$driverName][null === $alias ? self::defaultAlias() : $alias]);
	}
554445
public function getSubqueryByAlias($alias)
    {
        return $this->hasSubqueryAlias($alias) ? $this->getExpression($this->getHash($alias)) : null;
    }
716452
public function setAlias($alias = null)
    {
        if (!empty($alias)) {
            $this->query['alias'] = $alias;
        } else {
            unset($this->query['alias']);
        }
        return $this;
    }
552727
public function removeAlias($alias)
    {
        if (isset($this->aliases[$alias])) {
            unset($this->aliases[$alias]);
            return true;
        }

        return false;
    }
868101
private function getCacheConfig(string $alias): ?string
    {
        //读配置文件 ,可以不指定
        $config = configDefault([], 'tablecache');
        foreach ($config as $type => $tables) {
            if ($tables == $alias) {
                return $type;
            }

            if (is_array($tables)) {
                foreach ($tables as $table) {
                    if ($table == $alias) {
                        return $type;
                    }
                }
            }
        }
        return null;
    }
1070352
protected function getValueForQuery($alias)
    {
        $value = $this->getConvertedValue($alias);
        
        return is_null($value) ? $this->getValue() : $value;
    }
88757
public function getType($alias)
    {
        if (array_key_exists($alias, $this->types)) {
            return $this->types[$alias];
        }

        return false;
    }
817850
public function load($alias)
    {
        if (array_key_exists($alias, $this->aliases)) {
            return class_alias($this->aliases[$alias], $alias);
        }

        return false;
    }
924161
public final function alias($alias) {
        $this->alias         = $alias;
        $this->qualifiedName = $this->table . ' AS ' . $this->alias;

        return $this;
    }
712961
public function resolveClassAlias($alias)
    {
        $alias = static::normalise($alias);

        if (isset($this->classAliases[$alias])) {
            return $this->classAliases[$alias];
        }

        return $alias;
    }
1186767
public function has($alias)
    {
        $alias = $this->normalizeNamespace($alias);

        if (isset($this->byAlias[$alias]) || isset($this->byEntity[$alias])) {
            return true;
        }

        return false;
    }
898366
public function findOneByAlias($alias)
    {
        $query = $this->createValuedQueryBuilder('c')
            ->where('c.alias = :alias')
            ->setParameter('alias', $alias)
            ->getQuery();

        return $query->useResultCache(true, self::CACHE_TTL)->getSingleResult();
    }
1359098
public function setAlias($name, $alias)
    {
        if ($alias === null && isset($this->aliases[$name])) {
            unset($this->aliases[$name]);
        } else {
            $this->aliases[$name] = $alias;
        }

        return $this;
    }
283927
public function getAlias($alias) {
		if (!is_string($alias)) {
			return $alias;
		}

		if (array_key_exists($alias, $this->aliases)) {
			return $this->aliases[$alias];
		}

		return $alias;
	}
1077950
public function get($alias)
    {
        return isset($this->services[$alias]) ? $this->services[$alias] : null;
    }
1079800
public function resolveNamespaceAlias(string $alias)
    {
        foreach ($this->namespaces as $namespace) {
            list($className, $aliasTo) = $namespace;

            if (false == strpos($alias, $aliasTo)) {
                if (!empty($aliasTo)) {
                    $alias = substr($alias, strlen($aliasTo) + 1);
                }

                return $this->getClassForNamespaceAlias($className.'\\'.$alias);
            }
        }

        return false;
    }
194321
function isExtendedService($alias)
    {
        $cAlias = $this->_normalizeName($alias);
        return isset($this->aliases[$cAlias]);
    }