Thanks for the quick update. I did not have the reflex to look into psycopg2 for this. But indeed, a custom SA type would help here too.
On Thursday, 26 October 2017 17:46:29 UTC+2, Mike Bayer wrote: > > On Thu, Oct 26, 2017 at 11:16 AM, Michel Albert <exh...@gmail.com > <javascript:>> wrote: > > I've run into an issue with tables containing the special "-infinity" > value > > in postgres. More precisely, when resolving relations on such tables. > > > > SQLAlchemy will convert the value "-infinity" into "datetime(1, 1, 1, 0 > , > > 0)" and try to find rows in the related table with that value. > > SQLAlchemy does not apply conversions of any kind to date values > except in the case of the SQLite dialect. In this case, you are > seeing the database driver's documented behavior: > > http://initd.org/psycopg/docs/usage.html#infinite-dates-handling > > The workaround they provide allows your case to work, note you need to > adapt to datetime, not date: > > import psycopg2.extensions > > class InfDateAdapter: > def __init__(self, wrapped): > self.wrapped = wrapped > def getquoted(self): > if self.wrapped == datetime.datetime.max: > return b"'infinity'::date" > elif self.wrapped == datetime.datetime.min: > return b"'-infinity'::date" > else: > return > psycopg2.extensions.DateFromPy(self.wrapped).getquoted() > > psycopg2.extensions.register_adapter(datetime.datetime, InfDateAdapter) > > This same adaptation can be applied at the SQLAlchemy level using > TypeDecorator. > > > > > > > This will > > obviously not match and return no rows. Using a "joinedload" on such > > relations will work, but then the backreference will have the same > issue. > > > > I've created a small runnable example here: > > https://gist.github.com/exhuma/3e7d0c7d176b41b208af684e55bcf020 > > > > It should be self explanatory. > > > > I have not tested this with positive "infinity" but I assume it will be > > converted into "datetime.datetime.max" and thus fall victim to the same > > issue. > > > > Any ideas for a workaround which does not involve modifying the values > in > > the DB? > > > > -- > > 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. > > --- > > 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+...@googlegroups.com <javascript:>. > > To post to this group, send email to sqlal...@googlegroups.com > <javascript:>. > > Visit this group at https://groups.google.com/group/sqlalchemy. > > For more options, visit https://groups.google.com/d/optout. > -- 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. --- 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.
