Handle invalid metadata for SQLDocumentStore

haystack/document_stores/sql.py

@@ -21,7 +21,7 @@
         ForeignKeyConstraint,
     )
     from sqlalchemy.ext.declarative import declarative_base
-    from sqlalchemy.orm import relationship, sessionmaker
+    from sqlalchemy.orm import relationship, sessionmaker, validates
     from sqlalchemy.sql import case, null
 except (ImportError, ModuleNotFoundError) as ie:
     from haystack.utils.import_utils import _optional_component_not_installed
@@ -73,6 +73,17 @@ class MetaDocumentORM(ORMBase):
         {},
     )  # type: ignore
 
+    valid_metadata_types = (str, int, float, bool, bytes, bytearray, type(None))
+
+    @validates("value")
+    def validate_value(self, key, value):
+        if not isinstance(value, self.valid_metadata_types):
+            raise TypeError(
+                f"Discarded metadata '{self.name}', since it has invalid type: {type(value).__name__}.\n"
+                f"SQLDocumentStore can accept and cast to string only the following types: {', '.join([el.__name__ for el in self.valid_metadata_types])}"
+            )
+        return value
+
 
 class LabelORM(ORMBase):
     __tablename__ = "label"
@@ -386,7 +397,12 @@ def write_documents(
             for doc in document_objects[i : i + batch_size]:
                 meta_fields = doc.meta or {}
                 vector_id = meta_fields.pop("vector_id", None)
-                meta_orms = [MetaDocumentORM(name=key, value=value) for key, value in meta_fields.items()]
+                meta_orms = []
+                for key, value in meta_fields.items():
+                    try:
+                        meta_orms.append(MetaDocumentORM(name=key, value=value))
+                    except TypeError as ex:
+                        logger.error(f"Document {doc.id} - {ex}")
                 doc_mapping = {
                     "id": doc.id,
                     "content": doc.to_dict()["content"],

test/document_stores/test_document_store.py

@@ -453,6 +453,30 @@ def test_write_document_meta(document_store: BaseDocumentStore):
     assert document_store.get_document_by_id("4").meta["meta_field"] == "test4"
 
 
+@pytest.mark.parametrize("document_store", ["sql"], indirect=True)
+def test_write_document_sql_invalid_meta(document_store: BaseDocumentStore):
+    documents = [
+        {
+            "content": "dict_with_invalid_meta",
+            "valid_meta_field": "test1",
+            "invalid_meta_field": [1, 2, 3],
+            "name": "filename1",
+            "id": "1",
+        },
+        Document(
+            content="document_object_with_invalid_meta",
+            meta={"valid_meta_field": "test2", "invalid_meta_field": [1, 2, 3], "name": "filename2"},
+            id="2",
+        ),
+    ]
+    document_store.write_documents(documents)
+    documents_in_store = document_store.get_all_documents()
+    assert len(documents_in_store) == 2
+
+    assert document_store.get_document_by_id("1").meta == {"name": "filename1", "valid_meta_field": "test1"}
+    assert document_store.get_document_by_id("2").meta == {"name": "filename2", "valid_meta_field": "test2"}
+
+
 def test_write_document_index(document_store: BaseDocumentStore):
     document_store.delete_index("haystack_test_one")
     document_store.delete_index("haystack_test_two")