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# Copyright 2014 Canonical Ltd.
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# This program is free software: you can redistribute it and/or modify it
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# under the terms of the GNU Affero General Public License version 3, as
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# published by the Free Software Foundation.
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranties of
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# MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
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# PURPOSE. See the GNU Affero General Public License for more details.
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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"""Migration script for the Non Functional Stats Service.
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This script is called when the service is installed, and any time the service
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is upgraded. It follows a few simple steps to manage the database version:
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1) Connecxt to the database, and read the version from the db_version table. If
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it doesn't exist, assume the version is -1.
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2) Scan the db_patches directory for files that end in '.sql'. The files must
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be named 'NNN-{name}.sql'. The NNN is the numeric order of the patches,
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3) Apply patches in order. Each patch is applied in a DB transaction, and after
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each patch we incriment the database revision number in the db_version
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table. As a special case, if we just upgraded to version '0', we create
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from nfss.database import get_connection_for_request
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connection = get_connection_for_request()
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current_version = get_current_database_version(connection)
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maximum_version = get_maximum_version()
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print("Current database version is: %d" % current_version)
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if current_version != maximum_version:
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"Database schema can be updated to version: %d" % maximum_version
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for new_version in range(current_version + 1, maximum_version + 1):
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upgrade_database_to_version(connection, new_version)
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def get_current_database_version(connection):
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cursor = connection.cursor()
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cursor.execute('SELECT version FROM db_version;')
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except psycopg2.ProgrammingError:
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# table doesn't exist, we have a blank database, and need to start from
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data = cursor.fetchone()
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# table exists, but contains no data - not sure what this means
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# as we should never get here. Let's assume version -1.
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def report_error(message):
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# TODO: replace with proper logging!
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sys.stderr.write(message + '\n')
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def get_maximum_version():
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"""Return the maximum version we can patch the database to."""
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patches = get_all_patch_paths()
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return int(patches[-1][:3])
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def get_all_patch_paths():
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patches_path = get_database_patch_dir()
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lambda f: re.match(r'\d{3}-.*.sql', f),
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os.listdir(patches_path)
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def get_patch_file_path_for_version(version_number):
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"""Given a database version number, get the path to a patch that upgrades
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the schema to that version.
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raise a RuntimeError if more than one file matches.
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get_database_patch_dir(),
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"%03d-*.sql" % version_number
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"More than one file matched for version %d: %r" % (
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version_number, matches)
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"No patch file found for version %d" % version_number
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def get_database_patch_dir():
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return os.path.abspath(
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os.path.dirname(__file__),
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def upgrade_database_to_version(connection, new_version):
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"""Do the work to upgrade the database to version 'new_version'.
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This function starts a transaction on 'connection', and will either
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commit or rollback the transaction before the function ends.
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On success the function returns None, on failure the function raises an
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Note: Only call this function if the database is at 'new_version' - 1.
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patch_file = get_patch_file_path_for_version(new_version)
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print("Upgrading to version %s ..." % new_version)
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cursor = connection.cursor()
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with open(patch_file, 'r') as patch:
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cursor.execute(patch.read())
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cursor.execute('CREATE TABLE db_version (version integer);')
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cursor.execute('INSERT INTO db_version (version) VALUES (0);')
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cursor.execute('UPDATE db_version SET version=%d'
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except Exception as err:
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print("Error: %s" % err)
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connection.rollback()
added
removed
nf-stats-service/nfss/db_migrate.py
