microsoft/graphrag · error · TypeError

CSVTableProvider only works with FileStorage backends for no

Error message

CSVTableProvider only works with FileStorage backends for now.

What it means

CSVTableProvider.child() creates a child provider by calling storage.child(name), then re-checks that the result is still a FileStorage (a child of a FileStorage normally is, but a custom Storage subclass could return something else). If the child storage is not file-backed, it raises TypeError to preserve the class invariant.

Source

Thrown at packages/graphrag-storage/graphrag_storage/tables/csv_table_provider.py:149

            encoding: Character encoding for reading/writing CSV files.
                Defaults to "utf-8".
        """
        return CSVTable(
            self._storage,
            table_name,
            transformer=transformer,
            truncate=truncate,
            encoding=encoding,
        )

    def child(self, name: str | None) -> "CSVTableProvider":
        """Create a child provider backed by a child storage namespace."""
        if name is None:
            return self
        child_storage = self._storage.child(name)
        if not isinstance(child_storage, FileStorage):
            msg = "CSVTableProvider only works with FileStorage backends for now."
            raise TypeError(msg)
        return CSVTableProvider(storage=child_storage)

View on GitHub (pinned to f40e9a26ce)

Solutions

1. Ensure your custom storage's child() returns a FileStorage (same class or subclass whose instances are FileStorage)
2. If you need non-file child storage, use a different table provider type for the child
3. name=None returns self unchanged — pass None when you want no namespacing

Example fix

# before
class MyStorage(FileStorage):
    def child(self, name):
        return BlobStorage(...)
# after
class MyStorage(FileStorage):
    def child(self, name):
        return MyStorage(self.root_dir / name)

child_store = provider._storage.child(name)
assert isinstance(child_store, FileStorage)

def safe_child_is_file(provider, name) -> bool:
    from graphrag_storage import FileStorage
    return isinstance(provider._storage.child(name), FileStorage)

When it happens

Trigger: Calling provider.child('sub') where the underlying storage's child() returns a non-FileStorage object — e.g. a custom FileStorage subclass whose child() builds a blob client, or a monkeypatched storage in tests.

Common situations: Extending GraphRAG with a custom storage class that subclasses FileStorage loosely; test doubles replacing child(); refactors of the storage layer changing child() return types.

Related errors

• CSVTableProvider only works with FileStorage backends for no
• StorageConfig.type '{storage_strategy}' is not registered in
• Could not find {filename} in storage!

AI-assisted analysis of microsoft/graphrag@f40e9a26ce (2026-08-27). Data as JSON: /api/errors/8d585876f8e4d108. Report an issue: GitHub.