94 lines
3.6 KiB
Python
94 lines
3.6 KiB
Python
# Copyright 2013 OpenStack Foundation
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# Copyright 2013 Red Hat, Inc.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import migrate
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import sqlalchemy
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# Different RDBMSs use different schemes for naming the Foreign Key
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# Constraints. SQLAlchemy does not yet attempt to determine the name
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# for the constraint, and instead attempts to deduce it from the column.
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# This fails on MySQL.
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def get_constraints_names(table, column_name):
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fkeys = [fk.name for fk in table.constraints
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if (column_name in fk.columns and
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isinstance(fk, sqlalchemy.ForeignKeyConstraint))]
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return fkeys
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# remove_constraints and add_constraints both accept a list of dictionaries
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# that contain:
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# {'table': a sqlalchemy table. The constraint is added to to dropped from
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# this table.
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# 'fk_column': the name of a column on the above table, The constraint
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# is added to or dropped from this column
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# 'ref_column':a sqlalchemy column object. This is the reference column
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# for the constraint.
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def remove_constraints(constraints):
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for constraint_def in constraints:
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constraint_names = get_constraints_names(constraint_def['table'],
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constraint_def['fk_column'])
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for constraint_name in constraint_names:
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migrate.ForeignKeyConstraint(
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columns=[getattr(constraint_def['table'].c,
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constraint_def['fk_column'])],
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refcolumns=[constraint_def['ref_column']],
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name=constraint_name).drop()
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def add_constraints(constraints):
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for constraint_def in constraints:
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if constraint_def['table'].kwargs.get('mysql_engine') == 'MyISAM':
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# Don't try to create constraint when using MyISAM because it's
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# not supported.
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continue
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ref_col = constraint_def['ref_column']
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ref_engine = ref_col.table.kwargs.get('mysql_engine')
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if ref_engine == 'MyISAM':
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# Don't try to create constraint when using MyISAM because it's
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# not supported.
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continue
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migrate.ForeignKeyConstraint(
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columns=[getattr(constraint_def['table'].c,
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constraint_def['fk_column'])],
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refcolumns=[constraint_def['ref_column']]).create()
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def rename_tables_with_constraints(renames, constraints, engine):
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"""Renames tables with foreign key constraints.
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Tables are renamed after first removing constraints. The constraints are
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replaced after the rename is complete.
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This works on databases that don't support renaming tables that have
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constraints on them (DB2).
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`renames` is a dict, mapping {'to_table_name': from_table, ...}
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"""
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if engine.name != 'sqlite':
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# Sqlite doesn't support constraints, so nothing to remove.
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remove_constraints(constraints)
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for to_table_name in renames:
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from_table = renames[to_table_name]
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from_table.rename(to_table_name)
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if engine != 'sqlite':
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add_constraints(constraints)
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