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ENH: enable server side cursors when chunksize is set #56742

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ENH: enable server side cursors when chunksize is set #56742

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ffe076f
ENH: enable server side cursors when chunksize is set.
skshetry Jan 5, 2024
07b363a
add simple test for execution_options
skshetry Jan 11, 2024
ed5611b
fix tests
skshetry Jan 12, 2024
27553f7
Merge branch 'main' into stream-results
skshetry Feb 21, 2024
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4 changes: 3 additions & 1 deletion pandas/io/sql.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1636,6 +1636,8 @@ def run_transaction(self):
def execute(self, sql: str | Select | TextClause, params=None):
"""Simple passthrough to SQLAlchemy connectable"""
args = [] if params is None else [params]
if self.returns_generator:
self.con.execution_options(stream_results=True)
if isinstance(sql, str):
return self.con.exec_driver_sql(sql, *args)
return self.con.execute(sql, *args)
Expand Down Expand Up @@ -1814,11 +1816,11 @@ def read_query(
read_sql

"""
self.returns_generator = chunksize is not None
result = self.execute(sql, params)
columns = result.keys()

if chunksize is not None:
self.returns_generator = True
return self._query_iterator(
result,
self.exit_stack,
Expand Down
18 changes: 18 additions & 0 deletions pandas/tests/io/test_sql.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1189,6 +1189,24 @@ def test_read_iris_table_chunksize(conn, request):
check_iris_frame(iris_frame)


@pytest.mark.parametrize("conn", sqlalchemy_connectable_iris)
def test_sqlalchemy_read_table_chunksize_stream_results(conn, request):
conn = request.getfixturevalue(conn)
with sql.SQLDatabase(conn) as pandasSQL:
assert list(pandasSQL.read_table("iris", chunksize=10000))
execution_options = pandasSQL.con.get_execution_options()
assert execution_options["stream_results"] is True


@pytest.mark.parametrize("conn", sqlalchemy_connectable_iris)
def test_sqlalchemy_read_sql_chunksize_stream_results(conn, request):
conn = request.getfixturevalue(conn)
with sql.SQLDatabase(conn) as pandasSQL:
assert list(pandasSQL.read_sql("SELECT * FROM iris", chunksize=10000))
execution_options = pandasSQL.con.get_execution_options()
assert execution_options["stream_results"] is True


@pytest.mark.parametrize("conn", sqlalchemy_connectable)
def test_to_sql_callable(conn, test_frame1, request):
conn = request.getfixturevalue(conn)
Expand Down