private function getKeys(): array
	{
		/* @var $result Key[] */
		$result = [];
		$rows = $this->connection->query("
			SELECT 
				[INDEX_NAME],
				[COLUMN_NAME],
				[INDEX_TYPE],
				[NON_UNIQUE],
				[SEQ_IN_INDEX]
			FROM [information_schema.STATISTICS] 
			WHERE [TABLE_SCHEMA] = %s
				AND [TABLE_NAME] = %s 
				AND [INDEX_NAME] != %s",
			$this->database,
			$this->name,
			'PRIMARY');
		foreach ($rows as $row) {
			$name = $row->INDEX_NAME;
			if (isset($result[$name])) {
				$obj = $result[$name];
			} else {
				$obj = new Key;
			}
			$obj->name = $name;
			$obj->addColumn($row->SEQ_IN_INDEX, $row->COLUMN_NAME);
			$obj->type = $row->INDEX_TYPE;
			$obj->unique = !$row->NON_UNIQUE;

			$result[$name] = $obj;
		}
		return $result;
	}