Fix divide by zero error when pyarrow table size comes out 0 (#368)

* Add a case when in-memory-size is also 0

* Add UTs

* bump version

deltacat/__init__.py

@@ -44,7 +44,7 @@
 
 deltacat.logs.configure_deltacat_logger(logging.getLogger(__name__))
 
-__version__ = "1.1.26"
+__version__ = "1.1.27"
 
 
 __all__ = [

deltacat/compute/resource_estimation/delta.py

@@ -188,7 +188,7 @@ def _estimate_resources_required_to_process_delta_using_file_sampling(
         sampled_on_disk_size += delta.manifest.entries[entry_index].meta.content_length
         sampled_num_rows += len(tbl)
 
-    if not sampled_on_disk_size:
+    if not sampled_on_disk_size or not sampled_in_memory_size:
         return EstimatedResources.of(
             memory_bytes=0,
             statistics=Statistics.of(

deltacat/tests/compute/resource_estimation/test_delta.py

@@ -437,6 +437,43 @@ def test_delta_manifest_parquet_when_file_sampling(
             == parquet_delta_with_manifest.meta.content_length
         )
 
+    def test_parquet_delta_when_file_sampling_and_arrow_size_zero(
+        self,
+        local_deltacat_storage_kwargs,
+        parquet_delta_with_manifest: Delta,
+        monkeypatch,
+    ):
+        params = EstimateResourcesParams.of(
+            resource_estimation_method=ResourceEstimationMethod.FILE_SAMPLING,
+            max_files_to_sample=2,
+        )
+
+        def mock_func(*args, **kwargs):
+            class MockedValue:
+                nbytes = 0
+
+                def __len__(self):
+                    return 0
+
+            return MockedValue()
+
+        monkeypatch.setattr(ds, "download_delta_manifest_entry", mock_func)
+
+        result = estimate_resources_required_to_process_delta(
+            delta=parquet_delta_with_manifest,
+            operation_type=OperationType.PYARROW_DOWNLOAD,
+            deltacat_storage=ds,
+            deltacat_storage_kwargs=local_deltacat_storage_kwargs,
+            estimate_resources_params=params,
+        )
+
+        assert parquet_delta_with_manifest.manifest is not None
+        assert result.memory_bytes == 0
+        assert (
+            result.statistics.on_disk_size_bytes
+            == parquet_delta_with_manifest.meta.content_length
+        )
+
     def test_delta_manifest_utsv_when_file_sampling(
         self, local_deltacat_storage_kwargs, utsv_delta_with_manifest: Delta
     ):