diff --git a/src/Bundle/ChillMainBundle/DependencyInjection/ChillMainExtension.php b/src/Bundle/ChillMainBundle/DependencyInjection/ChillMainExtension.php
index 6826f854c..1637ee098 100644
--- a/src/Bundle/ChillMainBundle/DependencyInjection/ChillMainExtension.php
+++ b/src/Bundle/ChillMainBundle/DependencyInjection/ChillMainExtension.php
@@ -32,9 +32,8 @@ use Chill\MainBundle\Doctrine\DQL\JsonAggregate;
 use Chill\MainBundle\Doctrine\DQL\JsonbExistsInArray;
 use Chill\MainBundle\Doctrine\DQL\Similarity;
 use Chill\MainBundle\Doctrine\DQL\OverlapsI;
-use Symfony\Component\DependencyInjection\Definition;
-use Symfony\Component\DependencyInjection\Reference;
 use Chill\MainBundle\Doctrine\DQL\Replace;
+use Chill\MainBundle\Doctrine\ORM\Hydration\FlatHierarchyEntityHydrator;
 use Chill\MainBundle\Doctrine\Type\NativeDateIntervalType;
 use Chill\MainBundle\Doctrine\Type\PointType;
 use Symfony\Component\HttpFoundation\Request;
@@ -186,6 +185,9 @@ class ChillMainExtension extends Extension implements PrependExtensionInterface,
                                 'OVERLAPSI' => OverlapsI::class,
                             ],
                         ],
+                        'hydrators' => [
+                            'chill_flat_hierarchy_list' => FlatHierarchyEntityHydrator::class,
+                        ],
                     ],
                 ],
         );
diff --git a/src/Bundle/ChillMainBundle/Doctrine/ORM/Hydration/FlatHierarchyEntityHydrator.php b/src/Bundle/ChillMainBundle/Doctrine/ORM/Hydration/FlatHierarchyEntityHydrator.php
new file mode 100644
index 000000000..ed7588f94
--- /dev/null
+++ b/src/Bundle/ChillMainBundle/Doctrine/ORM/Hydration/FlatHierarchyEntityHydrator.php
@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Chill\MainBundle\Doctrine\ORM\Hydration;
+
+use Doctrine\ORM\Internal\Hydration\ObjectHydrator;
+use Generator;
+
+final class FlatHierarchyEntityHydrator extends ObjectHydrator
+{
+    public const LIST = 'chill_flat_hierarchy_list';
+
+    protected function hydrateAllData(): array
+    {
+        $generator = $this->buildRecursively(
+            parent::hydrateAllData(),
+            static fn($value): iterable => $value->getChildren(),
+        );
+
+        $result = [];
+
+        foreach ($generator as $entity) {
+            // We cannot expect anything from the object entity
+            // so, we cannot expect it to have a ::getId() method.
+            // So we use spl_object_hash() instead.
+            $result += [spl_object_hash($entity) => $entity];
+        }
+
+        return array_values($result);
+    }
+
+    /**
+     * @param iterable<int, SocialIssue> $iterable
+     * @param callable(SocialIssue): iterable<int, SocialIssue> $childrenAccessor
+     *
+     * @return Generator<int, SocialIssue>
+     */
+    private function buildRecursively(iterable $iterable, callable $childrenAccessor): Generator
+    {
+        foreach ($iterable as $item)
+        {
+            yield $item;
+
+            yield from $this->buildRecursively($childrenAccessor($item), $childrenAccessor);
+        }
+    }
+}