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lazr_postgresql 0.0.1

LAZR postgresql specific support code.

Copyright (c) 2011, Canonical Ltd

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 3 only.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. GNU General Public License version 3 (see the file LICENSE).

lazr_postgresql contains various helpers used by Launchpad for PostgreSQL support. Primary amongst these is the Slony aware database migrations facility.

Dependencies

  • Python 2.6+

Usage

Database migrations

The upgrade tool will apply data migrations to PostgreSQL or Slony environments.

Each migration is a SQL file named patch-$major-$minor-$point-$type.sql. Major, minor and point are integers that provide a sequence for how patches are applied. The type tells the migration applier whether the migration should be applied in a normal transaction, directly to all the nodes in the cluster in a transaction, or direcly to all the nodes in a cluster outside of a transaction. These are indicated by 'std', 'direct' and 'concurrent'.

If a patch application is interrupted in anything other than 'standard' mode, manual cleanup may be required (e.g. because a half built index will be in place on some nodes).

For instance a file called patch-1-2-3-concurrent.sql will be applied in the following way on a non-Slony environment:

  • A transaction on the master will be opened and the row 1-2-3 added to the list of applied patches. This prevents other migrations being attempted simultaneously.
  • Then the contents of the patch file will be executed.
  • The end timestamp for the 1-2-3 row will be updated.
  • Finally the transaction is committed.

In a Slony environment the following would happen:

  • A transaction on the master will be opened and the row 1-2-3 added to the list of applied patches. This prevents other migrations being attempted simultaneously.
  • On all nodes the the contents of the patch file will be executed in separate connections outside of a transaction.
  • The end timestamp for the 1-2-3 row will be updated.
  • Finally the transaction is committed.

A single invocation of upgrade.py will only apply std, or direct + concurrent patches unless the --all parameter is given, when it will loop until all patches are applied.

More coming soon.

Installation

Either run setup.py in an environment with all the dependencies available, or add the working directory to your PYTHONPATH.

Development

Upstream development takes place at https://launchpad.net/lazr_postgresql. To setup a working area for development, if the dependencies are not immediately available, you can use ./bootstrap.py to create bin/buildout, then bin/py to get a python interpreter with the dependencies available.

To run the tests use the runner of your choice, the test suite is lazr_postgresql.tests.test_suite.

For instance:

$ bin/py -m testtools.run lazr_postgresql.tests.test_suite

If you have testrepository you can run the tests with it:

$ testr run
 
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