dc: try to fix dataset_stats for DataChain.from_storage() generated d…

…ataset (#151)

src/datachain/data_storage/warehouse.py

@@ -390,7 +390,9 @@ def dataset_stats(
         expressions: tuple[_ColumnsClauseArgument[Any], ...] = (
             sa.func.count(table.c.sys__id),
         )
-        if "size" in table.columns:
+        if "file__size" in table.columns:
+            expressions = (*expressions, sa.func.sum(table.c.file__size))
+        elif "size" in table.columns:
             expressions = (*expressions, sa.func.sum(table.c.size))
         query = select(*expressions)
         ((nrows, *rest),) = self.db.execute(query)

tests/func/test_datachain.py

@@ -4,6 +4,7 @@
 import pandas as pd
 import pytest
 
+from datachain.dataset import DatasetStats
 from datachain.lib.dc import DataChain
 from datachain.lib.file import File
 
@@ -205,3 +206,12 @@ def test_show_no_truncate(capsys, catalog):
     for i in range(3):
         assert client[i] in normalized_output
         assert details[i] in normalized_output
+
+
+def test_from_storage_dataset_stats(tmp_dir, catalog):
+    for i in range(4):
+        (tmp_dir / f"file{i}.txt").write_text(f"file{i}")
+
+    dc = DataChain.from_storage(tmp_dir.as_uri(), catalog=catalog).save("test-data")
+    stats = catalog.dataset_stats(dc.name, dc.version)
+    assert stats == DatasetStats(num_objects=4, size=20)