Batch objects in Branch.delete_objects calls (#285)

lakeFS supports a maximum of 1000 objects per `delete_objects()`
invocation, since that calls the object deletion API under the hood.
This limitation is not without precedent, and exists also e.g. on
AWS S3.

Hence, we batch delete objects on the client side, dispatching multiple
API calls in the cases where the deleted objects list contains more
than a thousand objects.

The threshold number of objects is currently hardcoded to 1000, since
that is the limitation of the lakeFS server.

src/lakefs_spec/spec.py

@@ -27,10 +27,12 @@
 
 from lakefs_spec.errors import translate_lakefs_error
 from lakefs_spec.transaction import LakeFSTransaction
-from lakefs_spec.util import md5_checksum, parse
+from lakefs_spec.util import batched, md5_checksum, parse
 
 logger = logging.getLogger("lakefs-spec")
 
+MAX_DELETE_OBJS = 1000
+
 
 class LakeFSFileSystem(AbstractFileSystem):
     """
@@ -713,12 +715,18 @@ def rm(
 
         with self.wrapped_api_call(rpath=path):
             branch = lakefs.Branch(repository, ref, client=self.client)
-            objgen = branch.objects(prefix=prefix, delimiter="" if recursive else "/")
+            objgen_batched = batched(
+                branch.objects(prefix=prefix, delimiter="" if recursive else "/"), n=MAX_DELETE_OBJS
+            )
             if maxdepth is None:
-                branch.delete_objects(obj.path for obj in objgen)
+                for objgen in objgen_batched:
+                    branch.delete_objects(obj.path for obj in objgen)
             else:
-                # nesting level is just the amount of "/"s in the path, no leading "/".
-                branch.delete_objects(obj.path for obj in objgen if obj.path.count("/") <= maxdepth)
+                for objgen in objgen_batched:
+                    # nesting level is just the amount of "/"s in the path, no leading "/".
+                    branch.delete_objects(
+                        obj.path for obj in objgen if obj.path.count("/") <= maxdepth
+                    )
 
             # Directory listing cache for the containing folder must be invalidated
             self.dircache.pop(self._parent(path), None)

src/lakefs_spec/util.py

@@ -5,9 +5,11 @@
 from __future__ import annotations
 
 import hashlib
+import itertools
 import os
 import re
-from typing import Any, Callable, Generator, Protocol
+import sys
+from typing import Any, Callable, Generator, Iterable, Protocol
 
 from lakefs_sdk import Pagination
 from lakefs_sdk import __version__ as __lakefs_sdk_version__
@@ -49,6 +51,22 @@ def depaginate(
         kwargs["after"] = resp.pagination.next_offset
 
 
+def batched(iterable: Iterable, n: int) -> Iterable[tuple]:
+    pyversion = tuple(sys.version_info[:3])
+    # itertools.batched was added in Python 3.12.
+    if pyversion >= (3, 12):
+        # TODO(nicholasjng): Remove once target Python version is 3.12
+        return itertools.batched(iterable, n)  # type: ignore
+    else:
+        # "roughly equivalent" block from
+        # https://docs.python.org/3/library/itertools.html#itertools.batched
+        if n < 1:
+            raise ValueError("n must be at least one")
+        iterator = iter(iterable)
+        while batch := tuple(itertools.islice(iterator, n)):
+            yield batch
+
+
 def md5_checksum(lpath: str | os.PathLike[str], blocksize: int = 2**22) -> str:
     """
     Calculate a local file's MD5 hash.