On Fri, Jul 22, 2016 at 3:25 PM, TomS. <pidev...@gmail.com> wrote: > On 07/19/2016 06:41 PM, Mike Bayer wrote: > > > > On 07/19/2016 11:51 AM, TomS. wrote: > > Hi, > > We have Flask app which uses SQLAlchemy. Weird error started to happen > recently. The difficulty is that we can't reproduce the error (/figure > out conditions causing issue) - maybe someone could help. Any hints/tips > would be appreciated. > > There is a part in the code which constructs IN in SQL: > > MyModel.id.in_(my_ids) > > For some cases my_ids is an empty list. It works without any problems, > but after some time the same query (using empty list) starts to raise an > exception: > > SAWarning: The IN-predicate on "MyModel.id" was invoked with an empty > sequence. This results in a contradiction, which nonetheless can be > expensive to evaluate. Consider alternative strategies for improved > performance. > > After restarting app, everything works again. > > The question is - why this exception is not risen always (although we > tried to run app with empty list directly), but after some time of app > execution (~1 day)? > > > It's not an exception, it's a warning. Python warnings by default emit only > once, see: > https://docs.python.org/2/library/warnings.html#the-warnings-filter > > Ok, this is the explanation why it doesn't show up regularly. Thank you. > > I don't know why SAWarning is treated as error. Here is the log: > > 2016-07-21 13:58:14,108 ERROR: Exception on /own [GET] > Traceback (most recent call last): > [...] > File > "/home/developer/.virtualenvs/rest/lib/python2.7/site-packages/sqlalchemy/util/langhelpers.py", > line 1297, in warn > warnings.warn(msg, exc.SAWarning, stacklevel=2) > SAWarning: The IN-predicate on "MyModel.id" was invoked with an empty > sequence. This results in a contradiction, which nonetheless can be > expensive to evaluate. > > I will also ask on Flask group, but maybe you know the reason - Flask config > regarding logging is as follow: > > import logging > > from logging.handlers import RotatingFileHandler > > logger_file_handler = RotatingFileHandler('my.log', maxBytes=1024 * 1024 * > 100, backupCount=20) > logger_file_handler.setLevel(logging.DEBUG) > logger_formatter = logging.Formatter(u'%(asctime)s %(levelname)s: > %(message)s') > > logger_file_handler.setFormatter(logger_formatter) > > logging.captureWarnings(True) > > app.logger.addHandler(logger_file_handler) > app.logger.setLevel(logging.DEBUG) > > There is no code which change behavior (by filter) of SAWarning to 'error' > ...
The python warnings system is completely separate from the logging system. Whether or not a particular warning is turned into an exception is driven by the "warnings filter": https://docs.python.org/2/library/warnings.html#the-warnings-filter I think you must be configuring the warnings filter somewhere, because by default this shouldn't raise an exception. Simon -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
