SQLAlchemy does not catch postgresql.exceptions.UniqueError

[András Tim]

SQLAlchemy does not catch postgresql.exceptions.UniqueError. In normal case SQLAlchemy catches all exceptions and make standardized exceptions.

This exception should be an sqlalchemy.exc.IntegrityError.

[Mike Bayer]

the reason this occurs is because py-postgresql is using a hack for their IntegrityError, by re-using an entirely different exception class with a different name:

>>> from postgresql.driver import dbapi20
>>> dbapi20.IntegrityError
<class 'postgresql.exceptions.ICVError'>

we'd have to rewrite our entire exception wrapping system to support this. py-postgresql hasn't had a release in three years and is a dead project; the psycopg2 project supports Python 3 and is an industry-wide standard for Python postgresql access. Can't you just use that ?

[Mike Bayer]

• Added support for the case of the misbehaving DBAPI that has pep-249 exception names linked to exception classes of an entirely different name, preventing SQLAlchemy's own exception wrapping from wrapping the error appropriately. The SQLAlchemy dialect in use needs to implement a new accessor :attr:.DefaultDialect.dbapi_exception_translation_map to support this feature; this is implemented now for the py-postgresql dialect. fixes #3421

→ <<cset d178707ecaeb>>

[András Tim]

Thank you!