fix: change partitioning schema from large to normal string for pyarrow<12

python/deltalake/writer.py

@@ -208,8 +208,26 @@ def write_deltalake(
     else:  # creating a new table
         current_version = -1
 
+    dtype_map = {
+        pa.large_string(): pa.string(),  # type: ignore
+    }
+
+    def _large_to_normal_dtype(dtype: pa.DataType) -> pa.DataType:
+        try:
+            return dtype_map[dtype]
+        except KeyError:
+            return dtype
+
     if partition_by:
-        partition_schema = pa.schema([schema.field(name) for name in partition_by])
+        if PYARROW_MAJOR_VERSION < 12:
+            partition_schema = pa.schema(
+                [
+                    pa.field(name, _large_to_normal_dtype(schema.field(name).type))
+                    for name in partition_by
+                ]
+            )
+        else:
+            partition_schema = pa.schema([schema.field(name) for name in partition_by])
         partitioning = ds.partitioning(partition_schema, flavor="hive")
     else:
         partitioning = None

python/tests/test_writer.py

@@ -841,6 +841,25 @@ def test_large_arrow_types(tmp_path: pathlib.Path):
     assert table.schema == dt.schema().to_pyarrow(as_large_types=True)
 
 
+def test_partition_large_arrow_types(tmp_path: pathlib.Path):
+    table = pa.table(
+        {
+            "foo": pa.array(["1", "1", "2", "2"], pa.large_string()),
+            "bar": pa.array([1, 2, 1, 2], pa.int64()),
+            "baz": pa.array([1, 1, 1, 1], pa.int64()),
+        }
+    )
+
+    write_deltalake(tmp_path, table, partition_by=["foo"])
+
+    dt = DeltaTable(tmp_path)
+    files = dt.files()
+    expected = ["foo=1", "foo=2"]
+
+    result = sorted([file.split("/")[0] for file in files])
+    assert expected == result
+
+
 def test_uint_arrow_types(tmp_path: pathlib.Path):
     pylist = [
         {"num1": 3, "num2": 3, "num3": 3, "num4": 5},