Add a test for parquet file splitting

tests/io/test_split_scan_tasks.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+import contextlib
+
+import pyarrow as pa
+import pyarrow.parquet as papq
+import pytest
+
+import daft
+
+
+@contextlib.contextmanager
+def override_merge_scan_tasks_configs(scan_tasks_min_size_bytes: int, scan_tasks_max_size_bytes: int):
+    old_execution_config = daft.context.get_context().daft_execution_config
+
+    try:
+        daft.set_execution_config(
+            scan_tasks_min_size_bytes=scan_tasks_min_size_bytes,
+            scan_tasks_max_size_bytes=scan_tasks_max_size_bytes,
+        )
+        yield
+    finally:
+        daft.set_execution_config(old_execution_config)
+
+
+@pytest.fixture(scope="function")
+def parquet_files(tmpdir):
+    """Writes 1 Parquet file with 10 rowgroups, each of 100 bytes in size"""
+    tbl = pa.table({"data": ["aaa"] * 100})
+    path = tmpdir / "file.pq"
+    papq.write_table(tbl, str(path), row_group_size=10, use_dictionary=False)
+
+    return tmpdir
+
+
+def test_split_parquet_read(parquet_files):
+    with override_merge_scan_tasks_configs(1, 10):
+        df = daft.read_parquet(str(parquet_files))
+        assert df.num_partitions() == 10, "Should have 10 partitions since we will split the file"