Fixed structure issues when

Workaround for creocoder/yii2-nested-sets#114

Fixes #3456

Author: brandonkelly

CHANGELOG-v3.md

@@ -11,6 +11,8 @@
 - Updated Twig to 2.12.
 
 ### Fixed
+- Fixed a SQL error that could occur when deleting an entry or category with three or more nested levels of elements. ([#3456](https://github.com/craftcms/cms/issues/3456))
+- Fixed a bug where deleting an entry or category with nested elements could leave the structure in a jumbled state.
 - Fixed a bug where the `resave/matrix-blocks` command would wittingly resave Matrix blocks even if they hadn’t been loaded with their content, resulting in lost content. ([#5030](https://github.com/craftcms/cms/issues/5030))
 
 ## 3.3.7 - 2019-10-03

src/services/Elements.php

@@ -1158,20 +1158,13 @@ public function deleteElement(ElementInterface $element, bool $hardDelete = fals
         $transaction = $db->beginTransaction();
         try {
             // First delete any structure nodes with this element, so NestedSetBehavior can do its thing.
-            /** @var StructureElementRecord[] $records */
-            $records = StructureElementRecord::findAll([
-                'elementId' => $element->id
-            ]);
-
-            foreach ($records as $record) {
+            while (($record = StructureElementRecord::findOne(['elementId' => $element->id])) !== null) {
                 // If this element still has any children, move them up before the one getting deleted.
-                /** @var StructureElementRecord[] $children */
-                $children = $record->children()->all();
-
-                foreach ($children as $child) {
+                while (($child = $record->children(1)->one()) !== null) {
                     $child->insertBefore($record);
+                    // Re-fetch the record since its lft and rgt attributes just changed
+                    $record = StructureElementRecord::findOne($record->id);
                 }
-
                 // Delete this element's node
                 $record->deleteWithChildren();
             }