[data] Add version support to read_lance

python/ray/data/_internal/datasource/lance_datasource.py

@@ -1,5 +1,5 @@
 import logging
-from typing import TYPE_CHECKING, Any, Dict, Iterator, List, Optional
+from typing import TYPE_CHECKING, Any, Dict, Iterator, List, Optional, Union
 
 import numpy as np
 
@@ -29,6 +29,7 @@ class LanceDatasource(Datasource):
     def __init__(
         self,
         uri: str,
+        version: Optional[Union[int, str]] = None,
         columns: Optional[List[str]] = None,
         filter: Optional[str] = None,
         storage_options: Optional[Dict[str, str]] = None,
@@ -45,7 +46,9 @@ def __init__(
         if filter is not None:
             self.scanner_options["filter"] = filter
         self.storage_options = storage_options
-        self.lance_ds = lance.dataset(uri=uri, storage_options=storage_options)
+        self.lance_ds = lance.dataset(
+            uri=uri, version=version, storage_options=storage_options
+        )
 
         match = []
         match.extend(self.READ_FRAGMENTS_ERRORS_TO_RETRY)

python/ray/data/read_api.py

@@ -4083,6 +4083,7 @@ def read_iceberg(
 def read_lance(
     uri: str,
     *,
+    version: Optional[Union[int, str]] = None,
     columns: Optional[List[str]] = None,
     filter: Optional[str] = None,
     storage_options: Optional[Dict[str, str]] = None,
@@ -4109,6 +4110,9 @@ def read_lance(
     Args:
         uri: The URI of the Lance dataset to read from. Local file paths, S3, and GCS
             are supported.
+        version: Load a specific version of the Lance dataset. This can be an
+            integer version number or a string tag. By default, the
+            latest version is loaded.
         columns: The columns to read. By default, all columns are read.
         filter: Read returns only the rows matching the filter. By default, no
             filter is applied.
@@ -4140,6 +4144,7 @@ def read_lance(
     """  # noqa: E501
     datasource = LanceDatasource(
         uri=uri,
+        version=version,
         columns=columns,
         filter=filter,
         storage_options=storage_options,

python/ray/data/tests/test_lance.py

@@ -194,6 +194,56 @@ def test_lance_write_max_rows_per_file(data_path):
     assert len(ds.get_fragments()) == 10
 
 
+@pytest.mark.parametrize("data_path", [lazy_fixture("local_path")])
+def test_lance_read_with_version(data_path):
+    # NOTE: Lance only works with PyArrow 12 or above.
+    pyarrow_version = get_pyarrow_version()
+    if pyarrow_version is not None and pyarrow_version < parse_version("12.0.0"):
+        return
+
+    # Write an initial dataset (version 1)
+    df1 = pa.table({"one": [2, 1, 3, 4, 6, 5], "two": ["b", "a", "c", "e", "g", "f"]})
+    setup_data_path = _unwrap_protocol(data_path)
+    path = os.path.join(setup_data_path, "test_version.lance")
+    lance.write_dataset(df1, path)
+
+    # Merge new data to create a later version (latest)
+    ds_lance = lance.dataset(path)
+    # Get the initial version
+    initial_version = ds_lance.version
+
+    df2 = pa.table(
+        {
+            "one": [1, 2, 3, 4, 5, 6],
+            "three": [4, 5, 8, 9, 12, 13],
+            "four": ["u", "v", "w", "x", "y", "z"],
+        }
+    )
+    ds_lance.merge(df2, "one")
+
+    # Default read should return the latest (merged) dataset.
+    ds_latest = ray.data.read_lance(path)
+
+    assert ds_latest.count() == 6
+    # Latest dataset should contain merged columns
+    assert "three" in ds_latest.schema().names
+
+    # Read the initial version and ensure it contains the original columns
+    ds_prev = ray.data.read_lance(path, version=initial_version)
+    assert ds_prev.count() == 6
+    assert ds_prev.schema().names == ["one", "two"]
+
+    values_prev = [[s["one"], s["two"]] for s in ds_prev.take_all()]
+    assert sorted(values_prev) == [
+        [1, "a"],
+        [2, "b"],
+        [3, "c"],
+        [4, "e"],
+        [5, "f"],
+        [6, "g"],
+    ]
+
+
 if __name__ == "__main__":
     import sys