review comment

haystack/document_stores/sql.py

@@ -408,29 +408,25 @@ def write_documents(
                 if "classification" in meta_fields:
                     meta_fields = self._flatten_classification_meta_fields(meta_fields)
                 vector_id = meta_fields.pop("vector_id", None)
-                meta_orms = []
-                for key, value in meta_fields.items():
-                    try:
-                        meta_orms.append(MetaDocumentORM(name=key, value=value))
-                    except TypeError as ex:
-                        logger.error("Document %s - %s", doc.id, ex)
-                doc_orm = DocumentORM(
-                    id=doc.id,
-                    content=doc.to_dict()["content"],
-                    content_type=doc.content_type,
-                    vector_id=vector_id,
-                    meta=meta_orms,
-                    index=index,
-                )
+                meta_orms = [MetaDocumentORM(name=key, value=value) for key, value in meta_fields.items()]
+                doc_mapping = {
+                    "id": doc.id,
+                    "content": doc.to_dict()["content"],
+                    "content_type": doc.content_type,
+                    "vector_id": vector_id,
+                    "meta": meta_orms,
+                    "index": index,
+                }
                 if duplicate_documents == "overwrite":
+                    doc_orm = DocumentORM(**doc_mapping)
                     # First old meta data cleaning is required
                     self.session.query(MetaDocumentORM).filter_by(document_id=doc.id).delete()
                     self.session.merge(doc_orm)
                 else:
-                    docs_orm.append(doc_orm)
+                    docs_orm.append(doc_mapping)
 
             if docs_orm:
-                self.session.add_all(docs_orm)
+                self.session.bulk_insert_mappings(DocumentORM, docs_orm)
 
             try:
                 self.session.commit()