fix(mysql): catch PyMySQL OperationalError exception

[maxibor]

Description of changes

When trying to connect to a mySQL backend, the following error can appear:

OperationalError: (pymysql.err.OperationalError) (1298, "Unknown or incorrect time zone: 'UTC'")
(Background on this error at: https://sqlalche.me/e/20/e3q8)

This is due to an exception generated by PyMySQL.
The exception, formerly generated by SQLAlchemy was already caught by Ibis since #6010, this PR adds a catching of the PyMySQL exception.

Issues closed

Resolves #7918

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[cpcloud]

@maxibor Thanks for the PR!

Why isn't catching sqlalchemy's OperationalError sufficient here?

[maxibor]

Seems like these are 2 different exceptions. The pymysql exception was anyway not caught in the current version of Ibis.

[cpcloud]

Makes sense!

It's not clear to me whether we need both exceptions.

Can you describe your MySQL setup?

• What version of MySQL are using?
• What distribution (MySQL, MariaDB, something else)

[maxibor]

Just copy pasting from #7918

mySQL 5.5.5
mariaDB 10.3.38
Ibis 7.2.0

[cpcloud]

OperationalError: (pymysql.err.OperationalError) (1298, "Unknown or incorrect time zone: 'UTC'")
(Background on this error at: https://sqlalche.me/e/20/e3q8)

This is a SQLAlchemy exception, and the (pymysql.err.OperationalError) bit indicates that the underlying exception type is coming from pymysql, but that's not the actual exception raised.

Does this PR address the issue for you?

[maxibor]

Yes, that's why I opened it ;)

[cpcloud]

Ah, got it. This probably because of the use of a raw cursor and since we're testing against a system that has this defined, the exception is never raised.

Hm, I wonder if there's a way we can test this.

[cpcloud]

LGTM.

This code path will change once we finish porting backends to the new sqlglot compilers, and we won't need to catch the sqlalchemy exception (just the pymysql one).

That said, this fixes a user-facing issue and isn't easily testable so I'm going to merge it.

[mysqldba-nandy]

excuse me, maybe you should use SET @@session.time_zone = '+00:00', MySQL/MariaDB can not recognize UTC by default, only if table mysql.time_zone is not empty.