Any updates to this Michael? I've been researching about this but couldn't find a better solution than parsing the error message with regex. Would love to hear if there's a better way of doing this.
On Saturday, December 20, 2014 at 12:52:49 AM UTC+5:30, Michael Bayer wrote: > > > > alchemy1 <veeruk...@hotmail.com <javascript:>> wrote: > > I'm using ORM and I've defined a unique constraint on a column, and I want > to prevent inserting another row with the same value for that column. For > example if you don't want 2 users with the same name. > > One way to prevent it would be to take the provided name and query the > user table to see if anyone has that name, and if not then insert the > record. The problem with this is that in between checking for the name and > inserting the name, someone else could have inserted a record with that > name. So is there any advantage to doing this? Is there any better way to > do it? > > If not, I suppose you'd want to handle the IntegrityError that SQLAlchemy > throws when it detects a unique constraint violation. But since > IntegrityError handles several types of types of violations, would checking > the string of the error message be the only way to ensure you're handling > the correct error condition, so that you can put a specific message like "A > user with that name already exists"? > > sqlalchemy.exc.IntegrityError: (IntegrityError) duplicate key value violates > unique constraint "name_of_constraint" > > If so, how can I use metadata to get the name of the particular constraint > I have in mind, so that I can search for it in the error message string? > I've tried looking through the MetaData API and have got this far but I am > stuck. I can't seem to find the constraint name set on the name column here. > > Base.metadata.tables.user.c.name > User.name.info > > > yes, the non-standardization of DBAPI errors is something SQLAlchemy as > yet has not tried to solve, though in very recent releases it has begun to > provide hooks so that these solutions can be rolled more liberally. The > way I’ve solved this in Openstack looks like this: > > > https://github.com/openstack/oslo.db/blob/0265aa4e01270b8fc7cab1266b8602e1921c9ddb/oslo/db/sqlalchemy/exc_filters.py#L93 > > that regular expression is built upon a larger system that ultimately > makes use of the SQLAlchemy handle_error() event, which is new in recent > 0.9 series. You can see that we pull the columns out of the exception > message itself. > > > > > > -- > 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 http://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.
