Okay, I guess I figured out why this happens. We are using the
mysql+mysqldb dialect and we were explicitly setting* 'client_flag': 0* which
by default is set to 2 in SQLAlchemy, thus
disabling CLIENT_FLAGS.FOUND_ROWS. Removing *'client_flag': 0 *or setting
it to *'client_flag': 2 *makes everything to work as expected.
What I don't understand, is why the disabled FOUND_ROWS causes
StaleDatError when the row was actually updated in the database? Could it
be because of a very small difference between the previous
datetime/timestamp and the update one?
On Friday, September 1, 2023 at 10:23:56 PM UTC+3 Mike Bayer wrote:
> unless the row is being deleted, this would possibly be a driver bug. the
> pymysql driver should work pretty well whereas mysql-connector I would stay
> away from. I would need more detail to reproduce beyond that, the SQL
> statement has nohting wrong with it.
>
> On Fri, Sep 1, 2023, at 12:09 PM, Dumitru Gîra wrote:
>
> Hi Mike,
> thanks for the quick response.
>
> These would be the debug logs for
>
> import requests
> for i in range(2):
> r = requests.put('http://0.0.0.0:8080/update-datetime')
> print(r.text, r.code)
>
> 2023-09-01 16:06:20,711 INFO sqlalchemy.engine.Engine SELECT DATABASE()
> 2023-09-01 16:06:20,711 INFO sqlalchemy.engine.Engine [raw sql] ()
> 2023-09-01 16:06:20,713 DEBUG sqlalchemy.engine.Engine Col ('DATABASE()',)
> 2023-09-01 16:06:20,713 DEBUG sqlalchemy.engine.Engine Row ('dbname',)
> 2023-09-01 16:06:20,714 INFO sqlalchemy.engine.Engine SELECT @@sql_mode
> 2023-09-01 16:06:20,714 INFO sqlalchemy.engine.Engine [raw sql] ()
> 2023-09-01 16:06:20,715 DEBUG sqlalchemy.engine.Engine Col ('@@sql_mode',)
> 2023-09-01 16:06:20,715 DEBUG sqlalchemy.engine.Engine Row
> ('ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION',)
> 2023-09-01 16:06:20,716 INFO sqlalchemy.engine.Engine SELECT
> @@lower_case_table_names
> 2023-09-01 16:06:20,716 INFO sqlalchemy.engine.Engine [raw sql] ()
> 2023-09-01 16:06:20,717 DEBUG sqlalchemy.engine.Engine Col
> ('@@lower_case_table_names',)
> 2023-09-01 16:06:20,717 DEBUG sqlalchemy.engine.Engine Row (0,)
> 2023-09-01 16:06:20,717 INFO sqlalchemy.engine.Engine BEGIN (implicit)
> 2023-09-01 16:06:20,719 INFO sqlalchemy.engine.Engine SELECT foo.id AS
> foo_id, foo.last_login AS foo_last_login, foo.name AS foo_name
> FROM foo
> WHERE foo.id = %s
> LIMIT %s
> 2023-09-01 16:06:20,719 INFO sqlalchemy.engine.Engine [generated in
> 0.00016s] (1, 1)
> 2023-09-01 16:06:20,720 DEBUG sqlalchemy.engine.Engine Col ('foo_id',
> 'foo_last_login', 'foo_name')
> 2023-09-01 16:06:20,720 DEBUG sqlalchemy.engine.Engine Row (1,
> datetime.datetime(2023, 9, 1, 16, 6, 12), '2023-09-01 15:50:46.029445')
> 2023-09-01 16:06:20,722 INFO sqlalchemy.engine.Engine UPDATE foo SET
> last_login=%s WHERE foo.id = %s
> 2023-09-01 16:06:20,722 INFO sqlalchemy.engine.Engine [generated in
> 0.00014s] (datetime.datetime(2023, 9, 1, 16, 6, 20, 721146), 1)
> 2023-09-01 16:06:20,723 INFO sqlalchemy.engine.Engine COMMIT
> 192.168.0.1 - - [01/Sep/2023 16:06:20] "PUT /update-datetime HTTP/1.1" 200
> -
> 2023-09-01 16:06:20,733 INFO sqlalchemy.engine.Engine BEGIN (implicit)
> 2023-09-01 16:06:20,733 INFO sqlalchemy.engine.Engine SELECT foo.id AS
> foo_id, foo.last_login AS foo_last_login, foo.name AS foo_name
> FROM foo
> WHERE foo.id = %s
> LIMIT %s
> 2023-09-01 16:06:20,733 INFO sqlalchemy.engine.Engine [cached since
> 0.01402s ago] (1, 1)
> 2023-09-01 16:06:20,734 DEBUG sqlalchemy.engine.Engine Col ('foo_id',
> 'foo_last_login', 'foo_name')
> 2023-09-01 16:06:20,735 DEBUG sqlalchemy.engine.Engine Row (1,
> datetime.datetime(2023, 9, 1, 16, 6, 21), '2023-09-01 15:50:46.029445')
> 2023-09-01 16:06:20,736 INFO sqlalchemy.engine.Engine UPDATE foo SET
> last_login=%s WHERE foo.id = %s
> 2023-09-01 16:06:20,736 INFO sqlalchemy.engine.Engine [cached since
> 0.01399s ago] (datetime.datetime(2023, 9, 1, 16, 6, 20, 735704), 1)
> 2023-09-01 16:06:20,737 INFO sqlalchemy.engine.Engine ROLLBACK
> 192.168.0.1 - - [01/Sep/2023 16:06:20] "PUT /update-datetime HTTP/1.1" 500
> -
> Traceback (most recent call last):
> File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 2548,
> in __call__
> return self.wsgi_app(environ, start_response)
> File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 2528,
> in wsgi_app
> response = self.handle_exception(e)
> File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 2525,
> in wsgi_app
> response = self.full_dispatch_request()
> File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1822,
> in full_dispatch_request
> rv = self.handle_user_exception(e)
> File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1820,
> in full_dispatch_request
> rv = self.dispatch_request()
> File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1796,
> in dispatch_request
> return
> self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
> File "/usr/src/app/sqa.py", line 69, in update_datetime
> db_session.commit()
> File "<string>", line 2, in commit
> File "/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/session.py",
> line 1454, in commit
> self._transaction.commit(_to_root=self.future)
> File "/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/session.py",
> line 832, in commit
> self._prepare_impl()
> File "/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/session.py",
> line 811, in _prepare_impl
> self.session.flush()
> File "/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/session.py",
> line 3449, in flush
> self._flush(objects)
> File "/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/session.py",
> line 3589, in _flush
> transaction.rollback(_capture_exception=True)
> File
> "/usr/local/lib/python3.8/site-packages/sqlalchemy/util/langhelpers.py",
> line 70, in __exit__
> compat.raise_(
> File "/usr/local/lib/python3.8/site-packages/sqlalchemy/util/compat.py",
> line 211, in raise_
> raise exception
> File "/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/session.py",
> line 3549, in _flush
> flush_context.execute()
> File
> "/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/unitofwork.py", line
> 456, in execute
> rec.execute(self)
> File
> "/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/unitofwork.py", line
> 630, in execute
> util.preloaded.orm_persistence.save_obj(
> File
> "/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/persistence.py",
> line 237, in save_obj
> _emit_update_statements(
> File
> "/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/persistence.py",
> line 1035, in _emit_update_statements
> raise orm_exc.StaleDataError(
> sqlalchemy.orm.exc.StaleDataError: UPDATE statement on table 'foo'
> expected to update 1 row(s); 0 were matched.
> On Friday, September 1, 2023 at 7:02:56 PM UTC+3 Mike Bayer wrote:
>
>
> a stale data error with date/time fields is usually a mismatch between the
> date/time value you have locally and the one that's in the database,.
> assuming you are using the datetime column as a "version_id" in your
> mapping. Issues like strings vs. datetimes and/or microseconds portions
> being present or non-present are the most common.
>
> would need to see SQL debug logging to have more insight / confirm that's
> the problem.
>
> On Fri, Sep 1, 2023, at 11:59 AM, Dumitru Gîra wrote:
>
> I have encountered a very strange behaviour and I don't know where to look
> further.
> I have a small API https://pastebin.com/qW01jNz8 with 2 endpoints: one to
> update the name (VARCHAR) and one to update the last_login (DATETIME).
>
> If I make 10 consecutive requests to /update-string - everything works as
> expected.
> If I make 10 consecutive requests to /update-datetime - the first request
> works and other 9 fail with sqlalchemy.orm.exc.StaleDataError.
> NOTE: putting a time.sleep(1) after every request does not raise the error
>
> Consecutive requests are being made using the simple snippet
> import requests
> for i in range(10):
> r = requests.put('http://0.0.0.0:8080/update-datetime')
> print(r.text, r.code)
>
> The source code and the logs are in above link and for the reference I am
> using:
> - MySQL 8.0, but the same happens with 5.7
> - mysqldb connector, but the same happens with pymysql
> - SQLAlchemy==1.4.49
>
> Is this related to MySQL and specifically to date/time related fields (as
> the same happens with TIMESTAMP) or can it be something from SQLAlchemy
> side?
> Any directions would be highly appreciated.
>
> Kind regards,
> Dumitru
>
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
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>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
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>
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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