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fix(devmanual): Drop outdated database.xml information

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Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>
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Christoph Wurst
2023-04-19 09:48:28 +02:00
parent 84e068b59a
commit c4861bcb6a
1 changed files with 3 additions and 34 deletions
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37
developer_manual/basics/storage/migrations.rst
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@@ -4,48 +4,17 @@
Migrations
==========
In the past, apps had a `appinfo/database.xml`-file which holds their database schema
for installation and update and was a functional method for installing apps which
had some trouble with upgrading apps (e.g. apps were not able to rename columns
without losing the data stored in the original column):
.. code-block:: php
<?xml version="1.0" encoding="ISO-8859-1" ?>
<database>
<name>*dbname*</name>
<create>true</create>
<overwrite>false</overwrite>
<charset>utf8</charset>
<table>
<name>*dbprefix*twofactor_backupcodes</name>
<declaration>
<field>
<name>id</name>
<type>integer</type>
<autoincrement>1</autoincrement>
<default>0</default>
<notnull>true</notnull>
<length>4</length>
</field>
...
The limitations of this method will be bypassed with migrations. A migration can
consist of 3 different methods:
Migrations change the database schema and operate in three steps:
* Pre schema changes
* Actual schema changes
* Schema changes
* Post schema changes
Apps can have multiple migrations, which allows a way more flexible updating process.
For example, you can rename a column while copying all the content with 3 steps
packed in 2 migrations.
After creating migrations for your current database and installation routine,
in order to make use of migrations, you need to delete the old `appinfo/database.xml`
file. The Nextcloud updater logic only allows to use one or the other.
But as soon as the `database.xml` file is gone, it will look for your migration
The Nextcloud updater logic will look for your migration
files in the apps `lib/Migration` folder.
.. note:: While in theory you can run any code in the pre- and post-steps, we