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feat: DB API cursors are now iterable (#618)
* feat: make DB API Cursors iterable

* Raise error if obtaining iterator of closed Cursor
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plamut committed Apr 16, 2021
1 parent f75dcdf commit e0b373d0e721a70656ed8faceb7f5c70f642d144
Showing with 29 additions and 1 deletion.
  1. +1 −1 google/cloud/bigquery/dbapi/_helpers.py
  2. +4 −0 google/cloud/bigquery/dbapi/cursor.py
  3. +24 −0 tests/unit/test_dbapi_cursor.py
@@ -276,7 +276,7 @@ def decorate_public_methods(klass):
"""Apply ``_raise_on_closed()`` decorator to public instance methods.
"""
for name in dir(klass):
if name.startswith("_"):
if name.startswith("_") and name != "__iter__":
continue

member = getattr(klass, name)
@@ -365,6 +365,10 @@ def setinputsizes(self, sizes):
def setoutputsize(self, size, column=None):
"""No-op, but for consistency raise an error if cursor is closed."""

def __iter__(self):
self._try_fetch()
return iter(self._query_data)


def _format_operation_list(operation, parameters):
"""Formats parameters in operation in the way BigQuery expects.
@@ -178,6 +178,7 @@ def test_raises_error_if_closed(self):
"fetchone",
"setinputsizes",
"setoutputsize",
"__iter__",
)

for method in method_names:
@@ -611,6 +612,29 @@ def test_executemany_w_dml(self):
self.assertIsNone(cursor.description)
self.assertEqual(cursor.rowcount, 12)

def test_is_iterable(self):
from google.cloud.bigquery import dbapi

connection = dbapi.connect(
self._mock_client(rows=[("hello", "there", 7), ("good", "bye", -3)])
)
cursor = connection.cursor()
cursor.execute("SELECT foo, bar, baz FROM hello_world WHERE baz < 42;")

rows_iter = iter(cursor)

row = next(rows_iter)
self.assertEqual(row, ("hello", "there", 7))
row = next(rows_iter)
self.assertEqual(row, ("good", "bye", -3))
self.assertRaises(StopIteration, next, rows_iter)

self.assertEqual(
list(cursor),
[],
"Iterating again over the same results should produce no rows.",
)

def test__format_operation_w_dict(self):
from google.cloud.bigquery.dbapi import cursor

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