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zzzeek opened this issue May 23, 2022 Discussed in #8023 · 9 comments
Open

standardize async dbapi exceptions with access pattern #8047

zzzeek opened this issue May 23, 2022 Discussed in #8023 · 9 comments
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asyncio engine engines, connections, transactions, isolation levels, execution options feature PRs (with tests!) welcome a fix or feature which is appropriate to be implemented by volunteers
Milestone
2.1

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@zzzeek
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zzzeek commented May 23, 2022

Discussed in #8023

I think we should try to hit this in terms of all the async dialects all of which have to do what we are doing here, which would be that we make a common mixin / base for all the async-adapted DBAPIs. for asyncpg it would be used here:

sqlalchemy/lib/sqlalchemy/dialects/postgresql/asyncpg.py

Lines 760 to 761 in 19f0566

class Error(Exception):
pass 

    from ..exc import EmulatedDBAPIException

    class Error(EmulatedDBAPIException):
        pass

that way people can look at EmulatedDBAPIException to see the fields, which would be like:

class EmulatedDBAPIException:
    """an exception class used to adapt non-DBAPI database driver exceptions
    into DBAPI exceptions"""

    message: str
    """string message indicating the error"""

    orig: Exception
    """the original driver-level exception object"""

that looks kind of boring so we can also add an accessor on

sqlalchemy/lib/sqlalchemy/exc.py

Line 525 in 19f0566

class DBAPIError(StatementError):
called "driver_exception". This would work similarly to how we have "dbapi_connection" / "driver_connection" on Connection.

that way someone that knows asyncpg can receive the top level SQLAlchemy DBAPIException and just refer to .driver_exception to get all the asyncpg fields.
@zzzeek zzzeek added engine engines, connections, transactions, isolation levels, execution options use case not really a feature or a bug; can be support for new DB features or user use cases not anticipated asyncio labels May 23, 2022
@zzzeek zzzeek added this to the 2.0 milestone May 23, 2022
@zzzeek zzzeek mentioned this issue May 23, 2022
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@CaselIT
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CaselIT commented May 23, 2022 •
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makes sense. this would also work for sync driver, only "dbapi_expection" / "driver_exception" would point to the same object

@zzzeek
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zzzeek commented Aug 3, 2022

if someone wants to work on this sooner, it can be 2.0, but for now not an urgent need here

@zzzeek zzzeek added feature and removed use case not really a feature or a bug; can be support for new DB features or user use cases not anticipated labels Aug 3, 2022
@zzzeek zzzeek modified the milestones: 2.0, 2.1 Aug 3, 2022
@amacfie-tc amacfie-tc mentioned this issue May 26, 2023
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@CaselIT CaselIT added the PRs (with tests!) welcome a fix or feature which is appropriate to be implemented by volunteers label May 27, 2023
@bhperry
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bhperry commented Aug 7, 2024

This would be great. Currently in order to catch nowait lock errors from asyncpg I am doing string search for "LockNotAvailable" in the error message. Would much prefer to have access to the actual asyncpg exception.

@DeoLeung
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DeoLeung commented Aug 8, 2024

looking forward to get the origin exception as well
currently I can do e.orig.pgcode and match to the origin exception

@bhperry
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bhperry commented Aug 8, 2024

Is pgcode an int code?

@DeoLeung
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DeoLeung commented Aug 9, 2024

nope, but looking at the asyncpg.exception, it seems ok to do .startswith('42') to match to SyntaxOrAcceessError, same of other Exceptions :)

@jmehnle
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jmehnle commented Apr 29, 2025

I believe I'm running into this issue. I'm running SQLAlchemy 2.0 on top of asyncpg, and when some database statement returns, e.g., a not_null_violation PostgreSQL error, SQLAlchemy raises a sqlalchemy.exc.IntegrityError exception. However, when I try to inspect that exception's orig attribute, what I see is an exception that, by its __str__ value, pretends to be a asyncpg.exceptions.NotNullViolationError exception (as I would expect) but in reality is some obscure custom exception class with the following inheritance chain:

  • sqlalchemy.dialects.postgresql.asyncpg.AsyncAdapt_asyncpg_dbapi.IntegrityError
  • sqlalchemy.dialects.postgresql.asyncpg.AsyncAdapt_asyncpg_dbapi.DatabaseError
  • sqlalchemy.dialects.postgresql.asyncpg.AsyncAdapt_asyncpg_dbapi.Error
  • Exception
  • BaseException

I think https://docs.sqlalchemy.org/en/20/core/exceptions.html#sqlalchemy.exc.DBAPIError makes an attempt at explaining this, but unfortunately that explanation went completely past my head.

SQLAlchemy's IntegrityError exception is too general as I need to distinguish between not_null_violation, unique_violation, and other types of PostgreSQL errors that map to IntegrityError. How can I inspect the original exception without resorting to string matching? What is the reason that StatementError.orig doesn't actually expose the original exception but rather some chimera version of it?

@DeoLeung
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    except ProgrammingError as e:
      if e.orig.pgcode == UndefinedTableError.sqlstate:

hmmm, still string matching but a bit better workaround :)

@CaselIT
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CaselIT commented Apr 30, 2025

How can I inspect the original exception without resorting to string matching? What is the reason that StatementError.orig doesn't actually expose the original exception but rather some chimera version of it?

That was done to respect the pep249 exception hierarchy. The original exception is the cause of the custom pep249 excenption, since that's raised using raise new_exc from asyncpg_exc

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