public function clean() {

		// Defaults
		$has_delete = false;

		/** Delete topics/forums/posts ****************************************/

		$esc_like = $this->wpdb->esc_like( '_bbp_' ) . '%';
		$query    = ! empty( $this->sync_table )
			? $this->wpdb->prepare( "SELECT value_id FROM {$this->sync_table_name} INNER JOIN {$this->wpdb->posts} ON(value_id = ID) WHERE meta_key LIKE %s AND value_type = %s GROUP BY value_id ORDER BY value_id DESC LIMIT {$this->max_rows}", $esc_like, 'post' )
			: $this->wpdb->prepare( "SELECT post_id AS value_id FROM {$this->wpdb->postmeta} WHERE meta_key LIKE %s GROUP BY post_id ORDER BY post_id DESC LIMIT {$this->max_rows}", $esc_like );

		$posts = $this->get_results( $query, ARRAY_A );

		if ( isset( $posts[0] ) && ! empty( $posts[0]['value_id'] ) ) {
			foreach ( (array) $posts as $value ) {
				$deleted = wp_delete_post( $value['value_id'], true );

				// Only flag if not empty or error
				if ( ( false === $has_delete ) && ! empty( $deleted ) && ! is_wp_error( $deleted ) ) {
					$has_delete = true;
				}
			}
		}

		/** Delete users ******************************************************/

		$query = ! empty( $this->sync_table )
			? $this->wpdb->prepare( "SELECT value_id FROM {$this->sync_table_name} INNER JOIN {$this->wpdb->users} ON(value_id = ID) WHERE meta_key = %s AND value_type = %s LIMIT {$this->max_rows}", '_bbp_old_user_id', 'user' )
			: $this->wpdb->prepare( "SELECT user_id AS value_id FROM {$this->wpdb->usermeta} WHERE meta_key = %s LIMIT {$this->max_rows}", '_bbp_old_user_id' );

		$users = $this->get_results( $query, ARRAY_A );

		if ( ! empty( $users ) ) {
			foreach ( $users as $value ) {
				$deleted = wp_delete_user( $value['value_id'] );

				// Only flag if not empty or error
				if ( ( false === $has_delete ) && ! empty( $deleted ) && ! is_wp_error( $deleted ) ) {
					$has_delete = true;
				}
			}
		}

		unset( $posts );
		unset( $users );

		return ! $has_delete;
	}