Because 006_mysql_downgrade didn't correctly quote 'key' column [0][1] of 'image_properties' table when creating index [2],
the index wasn't created as needed, and then operator could not run any upgrade script successfully since
006_mysql_upgrade script could not to handle this unexpected db status [3].
[0] http://dev.mysql.com/doc/mysqld-version-reference/en/mysqld-version-reference-reservedwords-5-5.html
[1] http://dev.mysql.com/doc/mysqld-version-reference/en/mysqld-version-reference-reservedwords-5-0.html
[2] https://github.com/openstack/glance/blob/master/glance/db/sqlalchemy/migrate_repo/versions/006_mysql_downgrade.sql#L11
[3] https://github.com/openstack/glance/blob/master/glance/db/sqlalchemy/migrate_repo/versions/006_mysql_upgrade.sql#L5
Note, this issue doesn't impact one-way upgrade migration operation, since bug existed in downgrade script. But once operator
do a reciprocating migration operation, this issue will rise up. When I open "snake walk" mode on migration test, this issue
could be triggered as well.
======================================================================
FAIL: glance.tests.unit.test_migrations.TestMigrations.test_walk_versions
tags: worker-0
----------------------------------------------------------------------
Traceback (most recent call last):
File "glance/tests/unit/test_migrations.py", line 251, in test_walk_versions
self._walk_versions(engine, self.snake_walk)
File "glance/tests/unit/test_migrations.py", line 345, in _walk_versions
self._migrate_up(engine, version)
File "glance/tests/unit/test_migrations.py", line 394, in _migrate_up
version)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/migrate/versioning/api.py", line 186, in upgrade
return _migrate(url, repository, version, upgrade=True, err=err, **opts)
File "<string>", line 2, in _migrate
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/migrate/versioning/util/__init__.py", line 160, in with_engine
return f(*a, **kw)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/migrate/versioning/api.py", line 366, in _migrate
schema.runchange(ver, change, changeset.step)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/migrate/versioning/schema.py", line 93, in runchange
change.run(self.engine, step)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/migrate/versioning/script/sql.py", line 43, in run
conn.execute(text)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 721, in execute
return self._execute_text(object, multiparams, params)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 870, in _execute_text
statement, parameters
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 958, in _execute_context
context)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1160, in _handle_dbapi_exception
exc_info
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/util/compat.py", line 199, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 951, in _execute_context
context)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 436, in do_execute
cursor.execute(statement, parameters)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/MySQLdb/cursors.py", line 205, in execute
self.errorhandler(self, exc, value)
File "/home/lzy/workspace/openstack/glance/.tox/py27/local/lib/python2.7/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
raise errorclass, errorvalue
OperationalError: (OperationalError) (1091, "Can't DROP 'ix_image_properties_image_id_key'; check that column/key exists") '/*\n * This file is necessary because MySQL does not support\n * renaming indexes.\n */\nDROP INDEX ix_image_properties_image_id_key ON image_properties;\n\n/* Rename the `key` column to `name` */\nALTER TABLE image_properties\nCHANGE COLUMN `key` name VARCHAR(255) NOT NULL;\n\nCREATE UNIQUE INDEX ix_image_properties_image_id_name ON image_properties (image_id, name);\n' ()
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