MySQL requires a “type” for a drop constraint, so that the directive knows what specific DROP command to emit on MySQL. Other databases don’t have this limitation which is why there’s a “drop_constraint” in the first place, as opposed to “drop_foreign_key”, “drop_check_constraint”, etc.
from http://alembic.readthedocs.org/en/latest/ops.html#alembic.operations.Operations.drop_constraint: type_ – optional, required on MySQL. can be ‘foreignkey’, ‘primary’, ‘unique’, or ‘check’. On Dec 30, 2013, at 1:08 AM, Wesley <nisp...@gmail.com> wrote: > Hi , > I got the following error when do downgrade operation. > > [root@localhost PushServer]# alembic downgrade base > INFO [alembic.migration] Context impl MySQLImpl. > INFO [alembic.migration] Will assume non-transactional DDL. > INFO [alembic.migration] Running downgrade 3cb78fe040f4 -> 4bfc6a00969f, > delete name2 > Traceback (most recent call last): > File "/usr/bin/alembic", line 9, in <module> > load_entry_point('alembic==0.6.2', 'console_scripts', 'alembic')() > File "/usr/lib/python2.6/site-packages/alembic/config.py", line 298, in main > CommandLine(prog=prog).main(argv=argv) > File "/usr/lib/python2.6/site-packages/alembic/config.py", line 293, in main > self.run_cmd(cfg, options) > File "/usr/lib/python2.6/site-packages/alembic/config.py", line 279, in > run_cmd > **dict((k, getattr(options, k)) for k in kwarg) > File "/usr/lib/python2.6/site-packages/alembic/command.py", line 150, in > downgrade > script.run_env() > File "/usr/lib/python2.6/site-packages/alembic/script.py", line 199, in > run_env > util.load_python_file(self.dir, 'env.py') > File "/usr/lib/python2.6/site-packages/alembic/util.py", line 199, in > load_python_file > module = load_module(module_id, path) > File "/usr/lib/python2.6/site-packages/alembic/compat.py", line 55, in > load_module > mod = imp.load_source(module_id, path, fp) > File "alembic/env.py", line 77, in <module> > run_migrations_online() > File "alembic/env.py", line 70, in run_migrations_online > context.run_migrations() > File "<string>", line 7, in run_migrations > File "/usr/lib/python2.6/site-packages/alembic/environment.py", line 652, > in run_migrations > self.get_context().run_migrations(**kw) > File "/usr/lib/python2.6/site-packages/alembic/migration.py", line 225, in > run_migrations > change(**kw) > File "alembic/versions/3cb78fe040f4_delete_name2.py", line 29, in downgrade > op.drop_constraint(None, 'device') > File "<string>", line 7, in drop_constraint > File "<string>", line 1, in <lambda> > File "/usr/lib/python2.6/site-packages/alembic/util.py", line 294, in go > return fn(*arg, **kw) > File "/usr/lib/python2.6/site-packages/alembic/operations.py", line 775, in > drop_constraint > self.impl.drop_constraint(const) > File "/usr/lib/python2.6/site-packages/alembic/ddl/impl.py", line 138, in > drop_constraint > self._exec(schema.DropConstraint(const)) > File "/usr/lib/python2.6/site-packages/alembic/ddl/impl.py", line 76, in > _exec > conn.execute(construct, *multiparams, **params) > File > "/usr/lib/python2.6/site-packages/SQLAlchemy-0.8.3-py2.6-linux-x86_64.egg/sqlalchemy/engine/base.py", > line 662, in execute > params) > File > "/usr/lib/python2.6/site-packages/SQLAlchemy-0.8.3-py2.6-linux-x86_64.egg/sqlalchemy/engine/base.py", > line 714, in _execute_ddl > compiled = ddl.compile(dialect=dialect) > File > "/usr/lib/python2.6/site-packages/SQLAlchemy-0.8.3-py2.6-linux-x86_64.egg/sqlalchemy/sql/expression.py", > line 1920, in compile > return self._compiler(dialect, bind=bind, **kw) > File > "/usr/lib/python2.6/site-packages/SQLAlchemy-0.8.3-py2.6-linux-x86_64.egg/sqlalchemy/schema.py", > line 2954, in _compiler > return dialect.ddl_compiler(dialect, self, **kw) > File > "/usr/lib/python2.6/site-packages/SQLAlchemy-0.8.3-py2.6-linux-x86_64.egg/sqlalchemy/engine/interfaces.py", > line 787, in __init__ > self.string = self.process(self.statement, **compile_kwargs) > File > "/usr/lib/python2.6/site-packages/SQLAlchemy-0.8.3-py2.6-linux-x86_64.egg/sqlalchemy/engine/interfaces.py", > line 806, in process > return obj._compiler_dispatch(self, **kwargs) > File > "/usr/lib/python2.6/site-packages/SQLAlchemy-0.8.3-py2.6-linux-x86_64.egg/sqlalchemy/ext/compiler.py", > line 410, in <lambda> > lambda *arg, **kw: existing(*arg, **kw)) > File > "/usr/lib/python2.6/site-packages/SQLAlchemy-0.8.3-py2.6-linux-x86_64.egg/sqlalchemy/ext/compiler.py", > line 448, in __call__ > return fn(element, compiler, **kw) > File "/usr/lib/python2.6/site-packages/alembic/ddl/mysql.py", line 138, in > _mysql_drop_constraint > "No generic 'DROP CONSTRAINT' in MySQL - " > NotImplementedError: No generic 'DROP CONSTRAINT' in MySQL - please specify > constraint type > > Something related to database settings? how to fix this guy? > > Thanks. > Wesley > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy-alembic" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy-alembic+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out.
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