refactor: Ensure Flask framework leverages the Flask-SQLAlchemy session (Phase II) #26909

john-bodley · 2024-01-31T02:34:55Z

SUMMARY

This is a follow up to #26200 in order to try to rid the system of any non-global Flask-SQLAlchemy sessions (outside of Alembic migrations) via a more aggressive approach. This is somewhat of a prerequisite in order for us to define a consistent "unit of work" model.

Note I suspect passing of the SQLAlchemy session exists in part for testing purposes—though in reality one should never add code complexity to aid with testing when mocking is an option. Specifically there exists a mocked session with pre-loaded data which is leveraged by a slew of tests, however the session fixture (which relies on the get_session fixture), clearly mocks the Flask-SQLAlchemy session,

superset/tests/unit_tests/conftest.py

Line 65 in 73d118c

mocker.patch("superset.db.session", in_memory_session)

thus there's no need to reference the fixture session directly as db.session points to the same in memory session.

The TL;DR is this PR should provide a decent amount of code cleanup by removing unnecessary redundancy. I've also updated numerous tests to use db.session everywhere (as opposed to session or session_with_data) given it's monkey patched (as mentioned previously). This helps to ensure consistency throughout the code base which aids with readability. Additionally it reiterates that there is really only one session—the global Flask-SQLAlchemy session—which should be used.

The only place where passing db.session still persists in for functions which are related to Alembic migrations (including tests) as the migrations currently use a session other than the Flask-SQLAlchemy one. You can read more about that in #26172.

I've also declared that the db, sesh, and session variable be a disallowed name (even though there maybe the odd false positive). This should help prevent developers from trying to pass around either the global Flask-SQLAlchemy session or referencing another session as well as ensuring that we don't convolute the db name. There still exists instances where this is used, however this is deemed an anti-pattern which we should strive to remove.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

CI.

ADDITIONAL INFORMATION

Has associated issue:
Required feature flags:
Changes UI
Includes DB Migration (follow approval process in SIP-59)
- Migration is atomic, supports rollback & is backwards-compatible
- Confirm DB migration upgrade and downgrade tested
- Runtime estimates and downtime expectations provided
Introduces new feature or API
Removes existing feature or API

codecov · 2024-01-31T02:41:18Z

Codecov Report

Attention: 14 lines in your changes are missing coverage. Please review.

Comparison is base (e8e208d) 67.17% compared to head (77b87b0) 69.49%.

Files	Patch %	Lines
superset/utils/dashboard_import_export.py	0.00%	3 Missing ⚠️
superset/commands/dataset/importers/v1/utils.py	75.00%	2 Missing ⚠️
superset/commands/importers/v1/assets.py	80.00%	2 Missing ⚠️
superset/commands/importers/v1/examples.py	0.00%	2 Missing ⚠️
superset/cli/importexport.py	0.00%	1 Missing ⚠️
...perset/commands/dashboard/importers/v1/__init__.py	88.88%	1 Missing ⚠️
superset/connectors/sqla/utils.py	50.00%	1 Missing ⚠️
superset/models/dashboard.py	0.00%	1 Missing ⚠️
superset/tables/models.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #26909      +/-   ##
==========================================
+ Coverage   67.17%   69.49%   +2.32%     
==========================================
  Files        1900     1900              
  Lines       74443    74433      -10     
  Branches     8293     8293              
==========================================
+ Hits        50009    51730    +1721     
+ Misses      22379    20648    -1731     
  Partials     2055     2055

Flag	Coverage Δ
hive	`53.80% <31.96%> (?)`
mysql	`78.02% <86.06%> (-0.01%)`	⬇️
postgres	`78.12% <86.06%> (-0.01%)`	⬇️
presto	`53.75% <31.96%> (?)`
python	`83.08% <88.52%> (+4.82%)`	⬆️
sqlite	`77.64% <86.06%> (-0.01%)`	⬇️
unit	`56.42% <48.36%> (?)`

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john-bodley · 2024-01-31T06:02:19Z

superset/tags/models.py

@@ -131,7 +131,9 @@ def __str__(self) -> str:
        return f"<TaggedObject: {self.object_type}:{self.object_id} TAG:{self.tag_id}>"


-def get_tag(name: str, session: orm.Session, type_: TagType) -> Tag:


I left tags as is. The way we use SQLAlchemy event handlers isn't great as i) these aren't invoked for batch operations, and ii) we're mutating records other than the record associated with that callback which requires the use of a new session. Ideally these operations should be handled via commands.

michael-s-molina

Thank you for the cleanup work @john-bodley!

I left some first-pass comments. I tried to highlight the occurrences of session parameters that were not being used anymore but I definitely missed some. I suggest doing a full scan for unused session and session_with_data parameters.

michael-s-molina · 2024-02-01T20:41:46Z

tests/integration_tests/datasets/api_tests.py

@@ -1748,7 +1748,7 @@ def test_export_dataset(self):
        assert rv.status_code == 200

        cli_export = export_to_dict(
-            session=db.session,
+            db.session.db.session,


Suggested change

db.session.db.session,

Ha! My sed search and replace definitely screwed up a few things, but I thought I had addressed all of these given that CI was passing. Having mypy and pylint checks enabled for our tests would definitely be beneficial.

michael-s-molina · 2024-02-01T20:45:22Z

tests/integration_tests/explore/permalink/api_tests.py

@@ -39,7 +39,7 @@
 @pytest.fixture
 def chart(app_context, load_world_bank_dashboard_with_slices) -> Slice:
    session: Session = app_context.app.appbuilder.get_session


Suggested change

session: Session = app_context.app.appbuilder.get_session

michael-s-molina · 2024-02-01T20:50:11Z

tests/unit_tests/charts/commands/importers/v1/import_test.py

@@ -38,14 +39,14 @@ def test_import_chart(mocker: MockFixture, session: Session) -> None:

    mocker.patch.object(security_manager, "can_access", return_value=True)

-    engine = session.get_bind()
+    engine = db.session.get_bind()


Should we remove test_import_chart's session parameter as well?

See #26909 (comment).

michael-s-molina · 2024-02-01T20:55:56Z

tests/unit_tests/charts/dao/dao_tests.py

 from superset.utils.core import DatasourceType


 @pytest.fixture
 def session_with_data(session: Session) -> Iterator[Session]:
    from superset.models.slice import Slice

-    engine = session.get_bind()
+    engine = db.session.get_bind()


This change looks weird because the function is receiving a session via parameter to enhance it with data but in reality the parameter is not being used to process the request. Maybe we should remove the session parameter and rename the function to add_data_to_session or add_slice_to_session.

@michael-s-molina I'll revert the logic so that all fixtures augment the session fixture as opposed to db.session. Also I don't think these fixtures behave as the author(s) originally intended in terms of how the records are committed/rollbacked—though that's a headache for a different day.

michael-s-molina · 2024-02-01T20:56:38Z

tests/unit_tests/charts/dao/dao_tests.py

    yield session
-    session.rollback()
+    db.session.rollback()


 def test_slice_find_by_id_skip_base_filter(session_with_data: Session) -> None:


Suggested change

def test_slice_find_by_id_skip_base_filter(session_with_data: Session) -> None:

def test_slice_find_by_id_skip_base_filter() -> None:

See #26909 (comment).

michael-s-molina · 2024-02-01T21:17:09Z

tests/unit_tests/tables/test_models.py

 from sqlalchemy.orm.session import Session

+from superset import db
+

 def test_table_model(session: Session) -> None:


Suggested change

def test_table_model(session: Session) -> None:

def test_table_model() -> None:

michael-s-molina · 2024-02-01T21:17:25Z

tests/unit_tests/tags/commands/create_test.py

 from superset.utils.core import DatasourceType


 @pytest.fixture
 def session_with_data(session: Session):
+    from superset import db


Same comment as before about enhancing the session with data.

michael-s-molina · 2024-02-01T21:17:57Z

tests/unit_tests/tags/commands/create_test.py

+    db.session.add(saved_query)
+    db.session.add(dashboard_obj)
+    db.session.commit()
+    yield db.session


 def test_create_command_success(session_with_data: Session, mocker: MockFixture):


Suggested change

def test_create_command_success(session_with_data: Session, mocker: MockFixture):

def test_create_command_success(mocker: MockFixture):

See #26909 (comment).

michael-s-molina · 2024-02-01T21:18:21Z

tests/unit_tests/tags/commands/update_test.py

@@ -30,7 +31,7 @@ def session_with_data(session: Session):
    from superset.models.sql_lab import Query, SavedQuery
    from superset.tags.models import Tag

-    engine = session.get_bind()
+    engine = db.session.get_bind()


Same comment as before about enhancing the session with data.

See #26909 (comment).

michael-s-molina · 2024-02-01T21:19:01Z

tests/unit_tests/tags/commands/update_test.py

@@ -117,8 +120,8 @@ def test_update_command_success_duplicates(
    from superset.models.slice import Slice
    from superset.tags.models import ObjectType, TaggedObject

-    dashboard = session_with_data.query(Dashboard).first()
-    chart = session_with_data.query(Slice).first()
+    dashboard = db.session.query(Dashboard).first()


Remove session_with_data parameter?

See #26909 (comment).

john-bodley · 2024-02-01T21:56:25Z

Thanks @michael-s-molina for the review. I think there's a pytest pattern which can be somewhat confusing related to fixtures. There are numerous tests which have a signature of the form,

def test_foo(session: Session, ...):
    ...

or

def test_foo(session_with_data: Session, ...):
    ...

though these are in fact SQLAlchemy sessions (which can be accessed directly, i.e., session_with_data.query(...) they are pytest fixtures and their primary purpose in the function signature is for the test to leverage the fixture (given they're scope is non-global), i,.e., an in-memory session which may contain various objects (example) and thus are still required. These sessions are accessible via the Flask-SQLAlchemy global session (db.session) given that it's been patched here. The TL;DR you can think of these fixtures as providing the tests with pre-loaded ephemeral data which isn't persisted to the database. The challenge with fixtures (in conjunction with monkey patching) is that it's not overly apparent when reading the code how/where they are actually used.

Per the PR description I wanted to make it really clear that we should always be querying the session via the Flask-SQLAlchemy interface. It's a clearer/simpler pattern in my opinion.

…on (Phase II)

michael-s-molina

Thanks for addressing the comments @john-bodley.

The challenge with fixtures (in conjunction with monkey patching) is that it's not overly apparent when reading the code how/where they are actually used.

I'm not a fan of this pattern but I guess this is not in the scope of this PR so LGTM.

…on (Phase II) (apache#26909)

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refactor: Ensure Flask framework leverages the Flask-SQLAlchemy sessi…

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		@@ -131,7 +131,9 @@ def __str__(self) -> str:
		return f"<TaggedObject: {self.object_type}:{self.object_id} TAG:{self.tag_id}>"


		def get_tag(name: str, session: orm.Session, type_: TagType) -> Tag:

	def test_slice_find_by_id_skip_base_filter(session_with_data: Session) -> None:
	def test_slice_find_by_id_skip_base_filter() -> None:

	def test_table_model(session: Session) -> None:
	def test_table_model() -> None:

	def test_create_command_success(session_with_data: Session, mocker: MockFixture):
	def test_create_command_success(mocker: MockFixture):

refactor: Ensure Flask framework leverages the Flask-SQLAlchemy session (Phase II) #26909

refactor: Ensure Flask framework leverages the Flask-SQLAlchemy session (Phase II) #26909

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john-bodley commented Jan 31, 2024 • edited Loading

SUMMARY

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

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