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Preparing for data migration
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----------------------------
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Before starting a migration, there are a few important things to do
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1. Take a complete backup.
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2. Take some time to purge obsolete branches.
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A complete backup gives you a safety net in case anything goes wrong.
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Purging obsolete branches reduces the amount of data that needs to
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be migrated. See `Finding obsolete branches`_ later for some tips
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Introducing the upgrade-related commands
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----------------------------------------
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There are 3 important commands to be aware of when migrating data.
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* **check** - check a repository, branch or tree for data integrity errors
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* **reconcile** - fix data integrity errors
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* **upgrade** - migrate data to a different format.
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**reconcile** is rarely needed but it's good practice to run **check**
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before and after running **upgrade**.
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For detailed help on these commands, see the `Bazaar User Reference`_.
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.. _Bazaar User Reference: ../user-reference/index.html
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Communicating with your community
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---------------------------------
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To enable a smooth transition to the new format, you should:
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1. Make one person responsible for migrating the trunk.
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2. Test the migration of trunk works successfully.
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3. Schedule a time for the trunk migration and notify your community
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This advance warning should be long enough for users to have time
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to upgrade Bazaar and any required plugins before the migration date.
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For larger projects, allow some time for the migration itself.
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You should have a good idea of how long the migration will take
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after doing the test migration. It may make sense to do the migration
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on a weekend or a Friday, giving yourself some breathing space if
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After the trunk is migrated, you'll need to notify your community
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accordingly, giving them instructions as to how to migrate their
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local branches. Sample instructions are provided later in this
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Migrating a standalone branch
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-----------------------------
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2. If there are errors, try using **bzr reconcile** to fix them.
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If that fails, file a bug so we can help you resolve the issue
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and get your trunk clean. If it works, take a backup copy of
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2. Run **bzr upgrade --format** where *format* is 2a or later.
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3. Run **bzr check** to confirm the final result is good.
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Migrating branches in a shared repository
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-----------------------------------------
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Upgrade things in the following order:
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1. Upgrade the shared repository.
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2. Upgrade the branches.
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3. Upgrade any lightweight checkouts.
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As in the standalone branch case, be sure to run **check** before
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and after the upgrade to check for any existing or introduced issues.
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Migrating branches on Launchpad
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-------------------------------
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You have two options for upgrading your Launchpad branches. You can either
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upgrade them remotely or you can upgrade them locally and push the migrated
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branch to Launchpad. We recommend the latter. Upgrading remotely currently
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requires a fast, rock solid network connection to the Launchpad servers, and
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any interruption in that connection can leave you with a partially upgraded
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branch. The instructions below are the safest and often fastest way to
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upgrade your Launchpad branches.
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To allow isolation between public and private branches, Launchpad
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uses stacked branches rather than shared repositories as the core
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technology for efficient branch storage. The process for migrating
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to a new format for projects using Launchpad code hosting is therefore
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different to migrating a personal or in-house project.
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In Launchpad, a project can define a *development series* and associate a
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branch with that series. The branch then becomes the *focus of development*
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and gets special treatment and a shortcut url. By default, if anybody
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branches your project's focus of development and pushes changes back to
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Launchpad, their branch will be stacked on your development focus branch.
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Also, branches can be associated with other Launchpad artifacts such as bugs
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and merge proposals. All of these things mean that upgrading your focus of
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development branch is trickier.
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Here are the steps to follow:
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1. The nominated person grabs a copy of trunk and does the migration locally.
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2. On Launchpad, unset the current trunk from being the development focus.
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(This *must* be done or the following step won't work as expected.)
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1. Go to your project's home page on Launchpad
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2. Look for "XXX is the current focus of development"
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3. Click on the edit (pencil) icon
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4. Click on "Change details" in the portlet on the right
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5. Scroll down to where it says "Branch: (Optional)"
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6. Blank out this input field and click "Change"
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3. Push the migrated trunk to Launchpad. See below if you want your
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new migrated development focus branch to have the same name as your old
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pre-migration development focus branch.
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4. Set it as the development focus. Follow the instructions above but at step
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5, enter the name of the newly migrated branch you just pushed.
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5. Ask users subscribed to the old trunk to subscribe to the new one.
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In summary, these steps mean that the old trunk is still available and
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existing branches stacked on it will continue to be so. However, the
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development focus has switched to the migrated trunk and any new branches
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pushed to Launchpad for your project will now stack on it.
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You are now ready to tell your community that the new trunk is available
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and to give them instructions on migrating any local branches they have.
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If you want your new migrated development focus branch to have the same name
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as your old pre-migration branch, you need to do a few extra things before you
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establish the new development focus.
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1. Rename your old pre-migration branch; use something like
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**foo-obsolete-do-not-use**. You will really not want to delete this
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because there will be artifacts (bugs, merge proposals, etc.) associated
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2. Rename the new migrated branch to the pre-migration branch's old name.
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3. Re-establish the development focus branch using the new migrated branch's
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new name (i.e. the old pre-migration branch's original name).
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Migrating local branches after a central trunk has migrated
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-----------------------------------------------------------
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To migrate a standalone branch:
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1. Grab the latest branch from the central location into a
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2. Pull or merge any changes you've made in your existing branch
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To migrate branches in a shared repository:
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1. Create a fresh shared repository in the new format (2a or later).
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2. Grab the latest branch from the central location into a
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new directory inside the shared repository.
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3. Decide which of your local branches you want to migrate. (If you
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haven't already, now's a good time for `Finding obsolete branches`_
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and purging them, after backing up first of course.)
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4. To migrate each local branch of interest, there are 2 options:
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* **init** an empty branch in the new repository and **pull** the
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revisions from the branch in the old repository across.
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* In the new repository, **branch** from trunk to the new branch
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name then **merge** your changes from the matching branch in the
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The first method will give you a branch which is identical (in terms
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of revision history) to the old branch, but it's parent branch will
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be set to the old branch, not your new trunk. If you use this method,
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you'll probably want to edit your branch.conf file to update the
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parent branch setting.
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In contrast, the second approach sets up the parent branch correctly.
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However, it isn't ideal if you're not ready to include all the latest
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revisions from trunk into that branch yet.
added
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doc/en/upgrade-guide/data_migration.txt
