.. _backups:

================
Database Backups
================

Tabbycat doesn't provide an in-built database backup system; instead you should create
copies of your database directly. Heroku provides a very good backup utility for
all sites hosted on Heroku which makes this easy, and for Heroku-based Tabbycat
sites, we strongly recommend it.

You should **always** back up the database before deleting *any* data while in
the Edit Database area, because deleting data cannot be undone. It is also a
good idea to back up the database before doing anything in the Edit Database
area, unless you're very familiar and confident with editing the Tabbycat
database directly.

You may, as a matter of standard practice at large tournaments, wish to back up
the database twice per round: Once just after you've generated the draw and
allocated adjudicators, and once just after you've finished entering results.

If you're using an online version of Tabbycat, it's a good idea to download the
backups. While it's extremely rare to lose internet access or have an outage in
a critical web service (*i.e.*, Heroku), having a local copy of your backups
allows you to :ref:`restore your tab to a local installation <backup-restore-to-local>`
if this ever happens.

Installations on Heroku
=======================

Heroku provides a utility to easily back up and restore the entire site
database.

If you don't have the Heroku CLI
--------------------------------
You can capture backups from the Heroku Dashboard:

1. Go to the `Heroku Dashboard <http://dashboard.heroku.com/>`_ and click
   on your app.
2. Under *Installed add-ons*, click on **Heroku Postgres**.
3. Near the top left of the screen, click on the **Durability** tab.
4. Click on **Create Manual Backup**.
5. Once the capture has finished, a **Download** button will be available.

You can't restore a backup without the Heroku Command Line Interface (CLI), so
if you end up needing your backup, you'll need to install the
`Heroku CLI <https://devcenter.heroku.com/articles/heroku-cli>`_, and then
follow the instructions below.

If you have the Heroku CLI
--------------------------

The best guide to backing up databases is the
`Heroku Dev Center's PGBackups guide <https://devcenter.heroku.com/articles/heroku-postgres-backups>`_.

To capture a backup::

    $ heroku pg:backups:capture

To download the most recently captured backup::

    $ heroku pg:backups:download

To restore a backup::

    $ heroku pg:backups:restore

If you have multiple Tabbycat sites, you'll need to specify which one by adding
``--app mytournamentname`` to the end of the command.

Local installations
===================

There are lots of ways to back up local PostgreSQL databases, but we'd suggest
using the
`pg_dump <https://www.postgresql.org/docs/current/static/app-pgdump.html>`_
and
`pg_restore <https://www.postgresql.org/docs/current/static/app-pgrestore.html>`_
commands.

.. _backup-restore-to-local:

Restoring a Heroku backup to a local installation
=================================================

As detailed in the `Heroku Dev Center <https://devcenter.heroku.com/articles/heroku-postgres-import-export#restore-to-local-database>`_,
you can restore a downloaded Heroku backup to a local installation. This might
be useful if, say, your internet connection breaks irrecoverably in the middle
of a tournament and you need to run offline. Of course, for this to work, you
need to have downloaded your backup before your internet connection broke---a
good reason to download a copy of your backups as soon as you make them.

Assuming your download is called ``latest.dump`` (this is the default name), your PostgreSQL username is ``tabbycat``, and you wish to call your local database ``fromheroku`` (if not, replace arguments as appropriate)::

    $ createdb fromheroku -h localhost -U tabbycat
    $ pg_restore --no-acl --no-owner -h localhost -U tabbycat -d fromheroku latest.dump