Update docs for branches (#91)

* Update docs for branches

* Use yield from

README.md

@@ -114,7 +114,7 @@ print(catalog.datasets())
 
 ### Write and Read
 
-Append, delete some data. Each mutation generates a new version of data, represented by an increasing integer ID. We expect to support the [Iceberg](https://iceberg.apache.org/docs/latest/branching/) style tags and branches for better version management.
+Append, delete some data. Each mutation generates a new version of data, represented by an increasing integer ID. Users can add tags to version IDs as alias.
 ```py
 import pyarrow.compute as pc
 from space import RayOptions
@@ -170,12 +170,23 @@ runner.read_all(
 )
 
 # Read the changes between version 0 and 2.
-for change_type, data in runner.diff(0, "after_delete"):
-  print(change_type)
-  print(data)
+for change in runner.diff(0, "after_delete"):
+  print(change.change_type)
+  print(change.data)
   print("===============")
 ```
 
+Create a new branch and make changes in the new branch:
+
+```py
+# The default branch is "main"
+ds.add_branch("dev")
+ds.set_current_branch("dev")
+# Make changes in the new branch, the main branch is not updated.
+# Switch back to the main branch.
+ds.set_current_branch("main")
+```
+
 ### Transform and Materialized Views
 
 Space supports transforming a dataset to a view, and materializing the view to files. The transforms include:
@@ -285,7 +296,6 @@ ds.storage.record_manifest()  # Accept filter and snapshot_id
 Space is a new project under active development.
 
 :construction: Ongoing tasks:
-- Iceberg style version branches.
 - Performance benchmark and improvement.
 
 ## Disclaimer

python/pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "space-datasets"
-version = "0.0.10"
+version = "0.0.11"
 authors = [{ name = "Space team", email = "no-reply@google.com" }]
 description = "Unified storage framework for machine learning datasets"
 readme = "README.md"

python/src/space/core/ops/change_data.py

@@ -93,8 +93,7 @@ def read_change_data(storage: Storage, start_snapshot_id: int,
   """
   for snapshot_id in ordered_snapshot_ids(storage, start_snapshot_id,
                                           end_snapshot_id):
-    for change in LocalChangeDataReadOp(storage, snapshot_id, read_options):
-      yield change
+    yield from LocalChangeDataReadOp(storage, snapshot_id, read_options)
 
 
 class LocalChangeDataReadOp(StoragePathsMixin):

python/src/space/ray/ops/change_data.py

@@ -38,9 +38,8 @@ def read_change_data(storage: Storage, start_snapshot_id: int,
   """
   for snapshot_id in ordered_snapshot_ids(storage, start_snapshot_id,
                                           end_snapshot_id):
-    for change in _RayChangeDataReadOp(storage, snapshot_id, ray_options,
-                                       read_options):
-      yield change
+    yield from _RayChangeDataReadOp(storage, snapshot_id, ray_options,
+                                    read_options)
 
 
 class _RayChangeDataReadOp(LocalChangeDataReadOp):