Check Constraint support in MariaDB

[sqlalchemy-bot]

Migrated issue, originally created by MartinH (@dwt)

I just found out that MariaDB since version 10.2 supports check constraints

https://mariadb.com/kb/en/library/mariadb-1021-release-notes/
https://mariadb.com/kb/en/constraint/

yet when I try to drop one via alembic, I get this error

  File "/Users/dwt/.virtualenvs/yeepa/lib/python2.7/site-packages/alembic/ddl/mysql.py", line 340, in _mysql_drop_constraint
    "No generic 'DROP CONSTRAINT' in MySQL - "
NotImplementedError: No generic 'DROP CONSTRAINT' in MySQL - please specify constraint type

if I don't specify the constraint type 'check'. But if I do, I get this

  File "/Users/dwt/.virtualenvs/yeepa/lib/python2.7/site-packages/alembic/ddl/mysql.py", line 337, in _mysql_drop_constraint
    "MySQL does not support CHECK constraints.")
NotImplementedError: MySQL does not support CHECK constraints.

This is on alembic (0.9.7) - which I believe is the latest released version.

Is there kind of a flag I can set to work around this? Of course I also have production databases which don't yet support this flag...

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

see? that's why i hate putting in exception raises for things that the database would normally report an error towards, because suddenly the DB supports it.

There were actually a bunch of issues in MariaDB's CHECK constraints that I reported to them and got fixed, and SQLAlchemy 1.2 also made a lot of adjustments to work w/ mariadb 10.2.

but here, yes, we need DROP CONSTRAINT to at least work.

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• added labels: op directives

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• set milestone to "fasttrack"

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

Add DROP CONSTRAINT to MySQL for mariadb

Added support for DROP CONSTRAINT to the MySQL Alembic
dialect to support MariaDB 10.2 which now has real
CHECK constraints. Note this change does not
add autogenerate support, only support for op.drop_constraint()
to work.

Change-Id: I15b2425a44e4559b047b61573117fca9a46c8be3
Fixes: #479

→ 5b34e1c

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• changed status to closed

[sqlalchemy-bot]

MartinH (@dwt) wrote:

Wow, another stellar fast Michael Bayer fix time. Thanks a lot!