' . $expr . '~i', $request_uri ) ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * Checks for WordPress cookies.
	 *
	 * @return bool
	 */
	public function _check_cookies() {
		foreach ( array_keys( $_COOKIE ) as $cookie_name ) {
			if ( 'wordpress_test_cookie' === $cookie_name ) {
				continue;
			}
			if ( preg_match( '/^wp-postpass|^comment_author/', $cookie_name ) ) {
				return false;
			}
		}

		foreach ( $this->_config->get_array( 'dbcache.reject.cookie' ) as $reject_cookie ) {
			foreach ( array_keys( $_COOKIE ) as $cookie_name ) {
				if ( strstr( $cookie_name, $reject_cookie ) !== false ) {
					return false;
				}
			}
		}

		return true;
	}

	/**
	 * Check if user is logged in.
	 *
	 * @return bool
	 */
	public function _check_logged_in() {
		foreach ( array_keys( $_COOKIE ) as $cookie_name ) {
			if ( strpos( $cookie_name, 'wordpress_logged_in' ) === 0 ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * Get group.
	 *
	 * @access private
	 *
	 * @param string $sql SQL query.
	 *
	 * @return string
	 */
	private function _get_group( $sql ) {
		$sql = strtolower( $sql );

		// Collect list of tables used in query.
		if ( preg_match_all( '~(^|[\s,`])' . $this->wpdb_mixin->prefix . '([0-9a-zA-Z_]+)~i', $sql, $m ) ) {
			$tables = array_unique( $m[2] );
		} else {
			$tables = array();
		}

		if ( $this->contains_only_tables( $tables, array( 'options' => '*' ) ) ) {
			$group = 'options';
		} elseif (
			$this->contains_only_tables(
				$tables,
				array(
					'comments'     => '*',
					'commentsmeta' => '*',
				)
			) ) {
			$group = 'comments';
		} elseif ( count( $tables ) <= 1 ) {
			$group = 'singletables';   // Request with single table affected.
		} else {
			$group = 'remaining';
		}

		if ( $this->use_filters && function_exists( 'apply_filters' ) ) {
			$group = apply_filters( 'w3tc_dbcache_get_sql_group', $group, $sql, $tables );
		}

		return $group;
	}

	/**
	 * Contains only tables.
	 *
	 * @accress private
	 *
	 * @param array $tables  Tables.
	 *
	 * @param array $allowed Allowed.
	 */
	private function contains_only_tables( $tables, $allowed ) {
		if ( empty( $tables ) ) {
			return false;
		}

		foreach ( $tables as $t ) {
			if ( ! isset( $allowed[ $t ] ) ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * Get flush groups
	 *
	 * @access private
	 *
	 * @param string $group  Group.
	 *
	 * @param array  $extras Extra arguments.
	 */
	private function _get_flush_groups( $group, $extras = array() ) {
		$groups_to_flush = array();

		switch ( $group ) {
			case 'remaining':
			case 'singletables':
				$groups_to_flush = array(
					'remaining'    => '*',
					'options'      => '*',
					'comments'     => '*',
					'singletables' => '*',
				);
				break;
			/**
			 * Options are updated on each second request,
			 * ignore by default probability that SELECTs with joins with options are critical and don't flush "remaining".
			 * That can be changed by w3tc_dbcache_get_flush_groups filter.
			 */
			case 'options':
				$groups_to_flush = array( $group => '*' );
				break;
			default:
				$groups_to_flush = array(
					$group      => '*',
					'remaining' => '*',
				);
		}

		if ( $this->use_filters && function_exists( 'apply_filters' ) ) {
			$groups_to_flush = apply_filters( 'w3tc_dbcache_get_flush_groups', $groups_to_flush, $group, $extras );
		}

		return $groups_to_flush;
	}

	/**
	 * Get reject reason.
	 *
	 * @return string
	 */
	public function get_reject_reason() {
		if ( is_null( $this->cache_reject_reason ) ) {
			return '';
		}

		$request_wide_string = $this->cache_reject_request_wide ?
			( function_exists( '__' ) ? __( 'Request-wide ', 'w3-total-cache' ) : 'Request ' ) : '';

		return $request_wide_string . $this->_get_reject_reason_message( $this->cache_reject_reason );
	}

	/**
	 * Get reject reason message.
	 *
	 * @param string $key Key.
	 *
	 * @return string|void
	 */
	private function _get_reject_reason_message( $key ) {
		if ( ! function_exists( '__' ) ) {
			return $key;
		}

		switch ( $key ) {
			case 'dbcache.disabled':
				return __( 'Database caching is disabled', 'w3-total-cache' );
			case 'DONOTCACHEDB':
				return __( 'DONOTCACHEDB constant is defined', 'w3-total-cache' );
			case 'DOING_AJAX':
				return __( 'Doing AJAX', 'w3-total-cache' );
			case 'request':
				return __( 'Request URI is rejected', 'w3-total-cache' );
			case 'cookie':
				return __( 'Cookie is rejected', 'w3-total-cache' );
			case 'DOING_CRONG':
				return __( 'Doing cron', 'w3-total-cache' );
			case 'APP_REQUEST':
				return __( 'Application request', 'w3-total-cache' );
			case 'XMLRPC_REQUEST':
				return __( 'XMLRPC request', 'w3-total-cache' );
			case 'WP_ADMIN':
				return __( 'wp-admin', 'w3-total-cache' );
			case 'SHORTINIT':
				return __( 'Short init', 'w3-total-cache' );
			case 'query':
				return __( 'Query is rejected', 'w3-total-cache' );
			case 'user.logged_in':
				return __( 'User is logged in', 'w3-total-cache' );
			default:
				return $key;
		}
	}

	/**
	 * Footer comment.
	 *
	 * @param array $strings Strings.
	 *
	 * @return array
	 */
	public function w3tc_footer_comment( $strings ) {
		$reject_reason = $this->get_reject_reason();
		$append        = empty( $reject_reason ) ? '' : sprintf( ' (%1$s)', $reject_reason );

		if ( $this->query_hits ) {
			$strings[] = sprintf(
				// translators: 1: Query hits, 2: Total queries, 3: Total time, 4: Engine name, 5: Reject reason.
				__( 'Database Caching %1$d/%2$d queries in %3$.3f seconds using %4$s%5$s', 'w3-total-cache' ),
				$this->query_hits,
				$this->query_total,
				$this->time_total,
				Cache::engine_name( $this->_config->get_string( 'dbcache.engine' ) ),
				$append
			);
		} else {
			$strings[] = sprintf(
				// translators: 1: Engine name, 2: Reject reason.
				__( 'Database Caching using %1$s%2$s', 'w3-total-cache' ),
				Cache::engine_name( $this->_config->get_string( 'dbcache.engine' ) ),
				$append
			);
		}

		if ( $this->debug ) {
			$strings[] = '';
			$strings[] = __( 'Db cache debug info:', 'w3-total-cache' );
			$strings[] = sprintf( '%1$s%2$d', str_pad( __( 'Total queries: ', 'w3-total-cache' ), 20 ), $this->query_total );
			$strings[] = sprintf( '%1$s%2$d', str_pad( __( 'Cached queries: ', 'w3-total-cache' ), 20 ), $this->query_hits );
			$strings[] = sprintf( '%1$s%2$.4f', str_pad( __( 'Total query time: ', 'w3-total-cache' ), 20 ), $this->time_total );
		}

		if ( $this->log_filehandle ) {
			fclose( $this->log_filehandle ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_read_fclose
			$this->log_filehandle = false;
		}
		return $strings;
	}

	/**
	 * Usage statistics of request.
	 *
	 * @param object $storage Storage object.
	 *
	 * @return void
	 */
	public function w3tc_usage_statistics_of_request( $storage ) {
		$storage->counter_add( 'dbcache_calls_total', $this->query_total );
		$storage->counter_add( 'dbcache_calls_hits', $this->query_hits );
		$storage->counter_add( 'dbcache_flushes', $this->cache_flushes );
		$time_ms = (int) ( $this->time_total * 1000 );
		$storage->counter_add( 'dbcache_time_ms', $time_ms );
	}

	/**
	 * Log query.
	 *
	 * @access private
	 *
	 * @param string $line Line to add.
	 *
	 * @return void
	 */
	private function log_query( $line ) {
		if ( ! $this->log_filehandle ) {
			$filename             = Util_Debug::log_filename( 'dbcache-queries' );
			$this->log_filehandle = fopen( $filename, 'a' ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_read_fopen
		}

		fputcsv( $this->log_filehandle, $line, "\t" );
	}
}