Index: Classes/DataHandling/SlugHelper.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- Classes/DataHandling/SlugHelper.php	(date 1578649322835)
+++ Classes/DataHandling/SlugHelper.php	(date 1578649322835)
@@ -327,6 +327,50 @@
         return true;
     }
 
+    /**
+     * Check if there are other records with the same slug that are located in defined pid groups.
+     *
+     * @param string $slug
+     * @param RecordState $state
+     * @return bool
+     * @throws \TYPO3\CMS\Core\Exception\SiteNotFoundException
+     */
+    public function isUniqueInGroups(string $slug, RecordState $state): bool
+    {
+        $pageId = (int)$state->resolveNodeIdentifier();
+        $recordId = $state->getSubject()->getIdentifier();
+        $languageId = $state->getContext()->getLanguageId();
+
+        if ($pageId < 0) {
+            $pageId = $this->resolveLivePageId($recordId);
+        }
+
+        $queryBuilder = $this->createPreparedQueryBuilder();
+        $this->applySlugConstraint($queryBuilder, $slug);
+        $relevantPids = [$pageId];
+        foreach ($this->configuration["generatorOptions"]["pidGroups"] as $pidGroup) {
+            if (in_array($pageId, $pidGroup)) {
+                foreach ($pidGroup as $pid) {
+                    if (!in_array($pid, $relevantPids)) {
+                        $relevantPids[] = $pid;
+                    }
+                }
+            }
+        }
+        $this->applyPageIdConstraint($queryBuilder, $relevantPids);
+        $this->applyRecordConstraint($queryBuilder, $recordId);
+        if ($languageId != -1) {
+            $this->applyLanguageConstraint($queryBuilder, [-1, $languageId]);
+        }
+        $this->applyWorkspaceConstraint($queryBuilder);
+        $statement = $queryBuilder->execute();
+
+        $records = $this->resolveVersionOverlays(
+            $statement->fetchAll()
+        );
+        return count($records) === 0;
+    }
+
     /**
      * Generate a slug with a suffix "/mytitle-1" if that is in use already.
      *
@@ -380,6 +424,32 @@
         return $newValue;
     }
 
+    /**
+     * Generate a slug with a suffix "/mytitle-1" if the suggested slug is in use already.
+     *
+     * @param string $slug proposed slug
+     * @param RecordState $state
+     * @return string
+     */
+    public function buildSlugForUniqueInGroups(string $slug, RecordState $state): string
+    {
+        $slug = $this->sanitize($slug);
+        $rawValue = $this->extract($slug);
+        $newValue = $slug;
+        $counter = 0;
+        while (!$this->isUniqueInGroups(
+            $newValue,
+            $state
+        ) && $counter++ < 100
+        ) {
+            $newValue = $this->sanitize($rawValue . '-' . $counter);
+        }
+        if ($counter === 100) {
+            $newValue = $this->sanitize($rawValue . '-' . GeneralUtility::shortMD5($rawValue));
+        }
+        return $newValue;
+    }
+
     /**
      * @return QueryBuilder
      */
@@ -478,9 +548,9 @@
 
     /**
      * @param QueryBuilder $queryBuilder
-     * @param int $pageId
+     * @param int|array $pageId
      */
-    protected function applyPageIdConstraint(QueryBuilder $queryBuilder, int $pageId)
+    protected function applyPageIdConstraint(QueryBuilder $queryBuilder, $pageId)
     {
         if ($pageId < 0) {
             throw new \RuntimeException(
@@ -492,12 +562,21 @@
             );
         }
 
-        $queryBuilder->andWhere(
-            $queryBuilder->expr()->eq(
-                'pid',
-                $queryBuilder->createNamedParameter($pageId, \PDO::PARAM_INT)
-            )
-        );
+        if (is_array($pageId)) {
+            $queryBuilder->andWhere(
+                $queryBuilder->expr()->in(
+                    'pid',
+                    $queryBuilder->createNamedParameter($pageId, Connection::PARAM_INT_ARRAY)
+                )
+            );
+        } else {
+            $queryBuilder->andWhere(
+                $queryBuilder->expr()->eq(
+                    'pid',
+                    $queryBuilder->createNamedParameter($pageId, \PDO::PARAM_INT)
+                )
+            );
+        }
     }
 
     /**