NAME¶
Jifty::Manual::Upgrading - How-to change your application database over time
DESCRIPTION¶
Jifty provides a way for you to upgrade the database schema and data of your
application between versions. If all you are doing is adding new models or
columns to existing models Jifty will do the upgrade almost automatically. If
more extensive changes are required you need to write some code to tell Jifty
what to do.
TERMINOLOGY¶
Be sure you know the following terms before reading this document:
- •
- "schema" in Jifty::Manual::Glossary
- •
- "schema version" in Jifty::Manual::Glossary
- •
- "database version" in
Jifty::Manual::Glossary
HOW TO¶
General Instructions¶
For all of these actions, the the database version stored in your Jifty
configuration is significant. See the value stored in
etc/config.yml
at:
framework:
Database:
Version: 0.0.1
Make all your code changes using the version number
you are going to use.
Once you have finished updating your code and are ready to test, bump the
version stored in
etc/config.yml to match the new version you are going
to use.
If you are writing tests as you go (shame on you if you aren't!), you should be
able to run:
perl Makefile.PL
make
make test
to test the latest version and check for problems.
Once you are sure you've worked out the kinds, you may perform the actual
upgrade by running:
bin/jifty schema --setup
This will take care of the work of adding any new columns and models, dropping
old columns, and running any upgrade scripts you have scheduled.
Basic column and model operations¶
Adding a new model
Create your model just as you normally would:
bin/jifty model --name MyModel
Then, you need to tell Jifty at which version of your application the model was
created. To do this add a since sub to your new model class.
sub since { '0.0.5' }
Adding a new column to an existing model
When you have an existing model and decide that you need to add another column
to it you also need to tell Jifty about this. This is done by using
"since" as well. However, the "since" goes into the column
definition itself.
column created_by =>
refers_to Wifty::Model::User,
since '0.0.20';
Dropping a column from a model
CAUTION: Be aware that all the data that was stored in this column will
be destroyed at upgrade if you follow this procedure.
If you no longer need a particular column in your model, you can have it dropped
by setting the "till" property on your column definition.
column extra_info
type is 'text',
label is 'Extra info',
till '0.0.13';
The version you use for "till" is the version the drop is effective.
In the example above, the "extra_info" column will be available in
version 0.0.12, but not in version 0.0.13.
This column will be dropped from the schema at the next upgrade,
which will
destroy all data stored in that column.
TODO Dropping a model
Data migration and schema changes¶
If a file called
Upgrade.pm exists in your application it will be run by
"jifty schema --setup".
Upgrade.pm can be used to make any schema changes or to manipulate your
applications data.
At the very least your
Upgrade.pm should contain the following:
package MyApp::Upgrade;
use base qw(Jifty::Upgrade);
use Jifty::Upgrade qw( since rename );
since '0.6.1' => sub {
....
};
The "since" function is where you do all the work. Each
"since" will be run in version order until the application is up to
date.
Renaming a column
To rename a column, you need to make sure that your schema and upgrade script
both cooperate in the process. Your schema will record changes to your model
API and the upgrade script will tell Jifty about the rename.
The old column name needs to marked with "till" to notify Jifty that
the column name no longer exists. The new column name needs to marked with
"since" to notify Jifty that a column by the new name exists.
Here we are renaming "zip" to "postcode":
column zip =>
type is 'text',
label is 'ZIP code',
till '0.6.1';
column postcode =>
type is 'text',
label is 'Postal code',
since '0.6.1';
Notice that both "since" and "till" have the same version
number set. This is the version number the change will take place.
Before you upgrade, though, you must tell Jifty that a rename is happening here,
which is done in your upgrade script:
use MyApp::Upgrade;
use base qw(Jifty::Upgrade);
use Jifty::Upgrade qw( since rename );
since '0.6.1' => sub {
rename(
table => 'MyApp::Model::User',
column => 'zip',
to => 'postcode'
);
};
Migrating data
You can perform any action you want inside the "since" blocks of your
upgrade script. In the case of data migration, you might want to convert your
data from one form to another.
For example, let's say our users always gave us "first_name" and
"last_name" before, but we've added a new column
"display_name" which will normally contain their name in "last,
first" format, but could be customized per-account. We want to go ahead
and initialize this new column during the upgrade. In your upgrade script, you
could add:
since '0.2.4' => sub {
my $users = MyApp::Model::UserCollection->new(
current_user => Jifty->app_class('CurrentUser')->superuser
);
$users->unlimit;
while (my $user = $users->next) {
# error checks may save you from hours of debugging
my ($status, $msg) = $user->set_display_name(
join(', ', $user->last_name, $user->first_name)
);
Jifty->log->error("Couldn't change user record: $msg")
unless $status;
}
};
Note that collection created using super user to pass ACL checks and other
restrictions, if your models are protected from super user then you may have
problems. See also Jifty::Manual::AccessControl.
SEE ALSO¶
Jifty::Upgrade, Jifty::Script::Schema, Jifty::Manual::Models,
Jifty::Manual::Tutorial, Jifty::Manual::Glossary