本文整理汇总了Python中alembic.operations.Operations.drop_constraint方法的典型用法代码示例。如果您正苦于以下问题：Python Operations.drop_constraint方法的具体用法？Python Operations.drop_constraint怎么用？Python Operations.drop_constraint使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类alembic.operations.Operations的用法示例。
在下文中一共展示了Operations.drop_constraint方法的1个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的Python代码示例。
示例1: suspend_fk_constraints_for_col_alter
# 需要导入模块: from alembic.operations import Operations [as 别名]
# 或者: from alembic.operations.Operations import drop_constraint [as 别名]
def suspend_fk_constraints_for_col_alter(
engine, table_name, column_name, referents=[]):
"""Detect foreign key constraints, drop, and recreate.
This is used to guard against a column ALTER that on some backends
cannot proceed unless foreign key constraints are not present.
e.g.::
from oslo_db.sqlalchemy.util import (
suspend_fk_constraints_for_col_alter
)
with suspend_fk_constraints_for_col_alter(
migrate_engine, "user_table",
referents=[
"local_user", "nonlocal_user", "project"
]):
user_table.c.domain_id.alter(nullable=False)
:param engine: a SQLAlchemy engine (or connection)
:param table_name: target table name. All foreign key constraints
that refer to the table_name / column_name will be dropped and recreated.
:param column_name: target column name. all foreign key constraints
which refer to this column, either partially or fully, will be dropped
and recreated.
:param referents: sequence of string table names to search for foreign
key constraints. A future version of this function may no longer
require this argument, however for the moment it is required.
"""
if (
not ndb.ndb_status(engine)
):
yield
else:
with engine.connect() as conn:
insp = inspect(conn)
fks = []
for ref_table_name in referents:
for fk in insp.get_foreign_keys(ref_table_name):
if not fk.get('name'):
raise AssertionError("foreign key hasn't a name.")
if fk['referred_table'] == table_name and \
column_name in fk['referred_columns']:
fk['source_table'] = ref_table_name
if 'options' not in fk:
fk['options'] = {}
fks.append(fk)
ctx = MigrationContext.configure(conn)
op = Operations(ctx)
for fk in fks:
op.drop_constraint(
fk['name'], fk['source_table'], type_="foreignkey")
yield
for fk in fks:
op.create_foreign_key(
fk['name'], fk['source_table'],
fk['referred_table'],
fk['constrained_columns'],
fk['referred_columns'],
onupdate=fk['options'].get('onupdate'),
ondelete=fk['options'].get('ondelete'),
deferrable=fk['options'].get('deferrable'),
initially=fk['options'].get('initially'),
)