add tests

python/deltalake/table.py

@@ -674,8 +674,8 @@ def delete(self, predicate: Optional[str] = None) -> Dict[str, Any]:
         that contain records that satisfy the predicate. Once files are determined
         they are rewritten without the records.
 
-        :param predicate: a logical expression, defaults to None
-        :return: the metrics from delete
+        :param predicate: a SQL where clause. If not passed, will delete all rows.
+        :return: the metrics from delete.
         """
         metrics = self._table.delete(predicate)
         return json.loads(metrics)

python/tests/test_delete.py

@@ -0,0 +1,56 @@
+import pathlib
+
+import pyarrow as pa
+import pyarrow.compute as pc
+
+from deltalake.table import DeltaTable
+from deltalake.writer import write_deltalake
+
+
+def test_delete_no_predicates(existing_table: DeltaTable):
+    old_version = existing_table.version()
+
+    existing_table.delete()
+
+    last_action = existing_table.history(1)[0]
+    assert last_action["operation"] == "DELETE"
+    assert existing_table.version() == old_version + 1
+
+    dataset = existing_table.to_pyarrow_dataset()
+    assert dataset.count_rows() == 0
+
+
+def test_delete_a_partition(tmp_path: pathlib.Path, sample_data: pa.Table):
+    write_deltalake(tmp_path, sample_data, partition_by=["bool"])
+
+    dt = DeltaTable(tmp_path)
+    old_version = dt.version()
+
+    expr = pc.field("bool") != pc.scalar(True)
+    expected_table = sample_data.filter(expr)
+
+    dt.delete(predicate="bool = true")
+
+    last_action = dt.history(1)[0]
+    assert last_action["operation"] == "DELETE"
+    assert dt.version() == old_version + 1
+
+    table = dt.to_pyarrow_table()
+    assert table.equals(expected_table)
+    assert len(dt.files()) == 1
+
+
+def test_delete_some_rows(existing_table: DeltaTable):
+    old_version = existing_table.version()
+
+    expr = ~pc.field("utf8").isin(["0", "1"])
+    expected_table = existing_table.to_pyarrow_table().filter(expr)
+
+    existing_table.delete(predicate="utf8 in ('0', '1')")
+
+    last_action = existing_table.history(1)[0]
+    assert last_action["operation"] == "DELETE"
+    assert existing_table.version() == old_version + 1
+
+    table = existing_table.to_pyarrow_table()
+    assert table.equals(expected_table)