Database Exception – yii\db\Exception

     * Returns the PDO instance for the currently active master connection.
     * This method will open the master DB connection and then return [[pdo]].
     * @return PDO the PDO instance for the currently active master connection.
     */
    public function getMasterPdo()
    {
        $this->open();
        return $this->pdo;
    }
 
    /**
     * Returns the currently active slave connection.
     * If this method is called for the first time, it will try to open a slave connection when [[enableSlaves]] is true.

     * is available and `$fallbackToMaster` is false.
     */
    public function getSlavePdo($fallbackToMaster = true)
    {
        $db = $this->getSlave(false);
        if ($db === null) {
            return $fallbackToMaster ? $this->getMasterPdo() : null;
        }
 
        return $db->pdo;
    }
 
    /**

        // If the `$schemaCache` is an instance of `DbCache` we don't use it to avoid a loop
        if ($this->db->enableSchemaCache && $schemaCache instanceof CacheInterface && !($schemaCache instanceof DbCache)) {
            $cache = $schemaCache;
        }
        $version = $cache ? $cache->get($key) : null;
        if (!$version) {
            $version = $this->db->getSlavePdo()->getAttribute(\PDO::ATTR_SERVER_VERSION);
            if ($cache) {
                $cache->set($key, $version, $this->db->schemaCacheDuration);
            }
        }
 
        return version_compare($version, '5.6.4', '>=');

        $map = [
            Schema::TYPE_DATETIME => 'datetime',
            Schema::TYPE_TIMESTAMP => 'timestamp',
            Schema::TYPE_TIME => 'time',
        ];
 
        if ($this->supportsFractionalSeconds()) {
            $map = [
                Schema::TYPE_DATETIME => 'datetime(0)',
                Schema::TYPE_TIMESTAMP => 'timestamp(0)',
                Schema::TYPE_TIME => 'time(0)',
            ];
        }

     * {@inheritdoc}
     */
    public function init()
    {
        parent::init();
 
        $this->typeMap = array_merge($this->typeMap, $this->defaultTimeTypeMap());
    }
 
    /**
     * {@inheritdoc}
     */
    protected function defaultExpressionBuilders()

     */
    public function __construct($config = [])
    {
        if (!empty($config)) {
            Yii::configure($this, $config);
        }
        $this->init();
    }
 
    /**
     * Initializes the object.
     * This method is invoked at the end of the constructor after the object is initialized with the
     * given configuration.

     * @param Connection $connection the database connection.
     * @param array $config name-value pairs that will be used to initialize the object properties
     */
    public function __construct($connection, $config = [])
    {
        $this->db = $connection;
        parent::__construct($config);
    }
 
    /**
     * {@inheritdoc}
     */
    public function init()

    /**
     * Creates a query builder for the MySQL database.
     * @return QueryBuilder query builder instance
     */
    public function createQueryBuilder()
    {
        return new QueryBuilder($this->db);
    }
 
    /**
     * Resolves the table name and schema name (if any).
     * @param TableSchema $table the table metadata object
     * @param string $name the table name

    /**
     * @return QueryBuilder the query builder for this connection.
     */
    public function getQueryBuilder()
    {
        if ($this->_builder === null) {
            $this->_builder = $this->createQueryBuilder();
        }
 
        return $this->_builder;
    }
 
    /**

    /**
     * Returns the query builder for the current DB connection.
     * @return QueryBuilder the query builder for the current DB connection.
     */
    public function getQueryBuilder()
    {
        return $this->getSchema()->getQueryBuilder();
    }
 
    /**
     * Can be used to set [[QueryBuilder]] configuration via Connection configuration array.
     *
     * @param array $value the [[QueryBuilder]] properties to be configured.

        $modelClass = $this->modelClass;
        if ($db === null) {
            $db = $modelClass::getDb();
        }
 
        if ($this->sql === null) {
            list($sql, $params) = $db->getQueryBuilder()->build($this);
        } else {
            $sql = $this->sql;
            $params = $this->params;
        }
 
        $command = $db->createCommand($sql, $params);

    public function all($db = null)
    {
        if ($this->emulateExecution) {
            return [];
        }
 
        $rows = $this->createCommand($db)->queryAll();
 
        return $this->populate($rows);
    }
 
    /**
     * Converts the raw query results into the format as specified by this query.

     * @param Connection $db the DB connection used to create the DB command.
     * If null, the DB connection returned by [[modelClass]] will be used.
     * @return array|ActiveRecord[] the query results. If the query results in nothing, an empty array will be returned.
     */
    public function all($db = null)
    {
        return parent::all($db);
    }
 
    /**
     * {@inheritdoc}
     */
    public function prepare($builder)

    {
        $_obInitialLevel_ = ob_get_level();
        ob_start();
        ob_implicit_flush(false);
        extract($_params_, EXTR_OVERWRITE);
        try {
            require $_file_;
            return ob_get_clean();
        } catch (\Exception $e) {
            while (ob_get_level() > $_obInitialLevel_) {
                if (!@ob_end_clean()) {
                    ob_clean();
                }

                    $this->renderers[$ext] = Yii::createObject($this->renderers[$ext]);
                }
                /* @var $renderer ViewRenderer */
                $renderer = $this->renderers[$ext];
                $output = $renderer->render($this, $viewFile, $params);
            } else {
                $output = $this->renderPhpFile($viewFile, $params);
            }
            $this->afterRender($viewFile, $params, $output);
        }
 
        array_pop($this->_viewFiles);
        $this->context = $oldContext;

     * @throws InvalidCallException if the view cannot be resolved.
     * @see renderFile()
     */
    public function render($view, $params = [], $context = null)
    {
        $viewFile = $this->findViewFile($view, $context);
        return $this->renderFile($viewFile, $params, $context);
    }
 
    /**
     * Finds the view file based on the given view name.
     * @param string $view the view name or the [path alias](guide:concept-aliases) of the view file. Please refer to [[render()]]
     * on how to specify this parameter.

     * These parameters will not be available in the layout.
     * @return string the rendering result.
     * @throws InvalidArgumentException if the view file or the layout file does not exist.
     */
    public function render($view, $params = [])
    {
        $content = $this->getView()->render($view, $params, $this);
        return $this->renderContent($content);
    }
 
    /**
     * Renders a static string by applying a layout.
     * @param string $content the static string being rendered

        $args = $this->controller->bindActionParams($this, $params);
        Yii::debug('Running action: ' . get_class($this->controller) . '::' . $this->actionMethod . '()', __METHOD__);
        if (Yii::$app->requestedParams === null) {
            Yii::$app->requestedParams = $args;
        }
 
        return call_user_func_array([$this->controller, $this->actionMethod], $args);
    }
}

        }
 
        $result = null;
 
        if ($runAction && $this->beforeAction($action)) {
            // run the action
            $result = $action->runWithParams($params);
 
            $result = $this->afterAction($action, $result);
 
            // call afterAction on modules
            foreach ($modules as $module) {
                /* @var $module Module */

        $parts = $this->createController($route);
        if (is_array($parts)) {
            /* @var $controller Controller */
            list($controller, $actionID) = $parts;
            $oldController = Yii::$app->controller;
            Yii::$app->controller = $controller;
            $result = $controller->runAction($actionID, $params);
            if ($oldController !== null) {
                Yii::$app->controller = $oldController;
            }
 
            return $result;
        }

            $params = $this->catchAll;
            unset($params[0]);
        }
        try {
            Yii::debug("Route requested: '$route'", __METHOD__);
            $this->requestedRoute = $route;
            $result = $this->runAction($route, $params);
            if ($result instanceof Response) {
                return $result;
            }
 
            $response = $this->getResponse();
            if ($result !== null) {

    {
        try {
            $this->state = self::STATE_BEFORE_REQUEST;
            $this->trigger(self::EVENT_BEFORE_REQUEST);
 
            $this->state = self::STATE_HANDLING_REQUEST;
            $response = $this->handleRequest($this->getRequest());
 
            $this->state = self::STATE_AFTER_REQUEST;
            $this->trigger(self::EVENT_AFTER_REQUEST);
 
            $this->state = self::STATE_SENDING_RESPONSE;
            $response->send();