getRelationsByChild() public method

Retrieve products relations by childrens
public getRelationsByChild ( array $childrenIds ) : array
$childrenIds array The product ids being reindexed
return array
 /**
  * Process full-text reindex for product ids
  *
  * @param mixed $ids The product ids to reindex
  */
 protected function processFullTextIndex($ids)
 {
     $fullTextIndexer = $this->indexerRegistry->get(\Magento\CatalogSearch\Model\Indexer\Fulltext::INDEXER_ID);
     if (!is_array($ids)) {
         $ids = [$ids];
     }
     $parentIds = $this->fullIndexer->getRelationsByChild($ids);
     $processIds = $parentIds ? array_merge($parentIds, $ids) : $ids;
     if (!$fullTextIndexer->isScheduled()) {
         if (!empty($processIds)) {
             $fullTextIndexer->reindexList($processIds);
         }
     }
 }