Add lazy load fix

extensions/BlogPostFilter.php

@@ -17,4 +17,16 @@ class BlogPostFilter extends DataExtension {
 
 	}
 
+	/**
+	 * This is a fix so that when we try to fetch subclasses of BlogPost,
+	 * lazy loading includes the BlogPost table in its query. Leaving this table out
+	 * means the default sort order column PublishDate causes an error.
+	**/
+	public function augmentLoadLazyFields(SQLQuery &$query, &$dataQuery, $parent) {
+
+		// Ensures that we're joining the BlogPost table which holds required db fields.
+		$dataQuery->innerJoin("BlogPost", "`SiteTree`.`ID` = `BlogPost`.`ID`");
+
+	}
+
 }