Editing Manual/Upgrading (section)

===How hard is it to upgrade?=== <!--T:118-->

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If the only file you have modified is <tvar name=localsettings></tvar>, and you are upgrading from 1.5 or later, the process is very simple. The amount of human work involved is only a few minutes. The database schema changes will take an amount of time proportional to the size of your database — potentially hours for wikis with millions of pages, but for a more typical size of a few thousand pages, it is usually done in seconds.
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<translate><!--T:120--> Minor upgrades, within the same major version, say from <tvar name=1>.0</tvar> to <tvar name=2></tvar>, do not require any schema changes at all.</translate>
<translate><!--T:218--> You can just update the files. The database needs no update, hence it is not necessary to run the updater script.</translate>

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Upgrading from 1.4 or earlier is potentially complicated because support for character sets other than UTF-8 was dropped, and the schema for storing bulk text changed. Please read the relevant section in the <code>UPGRADE</code> file.

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Upgrading becomes difficult if you have modified our source code, and you don't want your changes to be overwritten. Tools such as <tvar name=diff>[http://www.gnu.org/software/diffutils/diffutils.html diff]</tvar>, <tvar name=patch>[http://www.gnu.org/software/patch/ patch]</tvar>, <tvar name=meld>[http://meldmerge.org/ Meld]</tvar> or <tvar name=winmerge>[http://winmerge.org/ WinMerge]</tvar> may be useful. There is also potential for trouble if you are using unmaintained extensions. Upgrade your extensions at the same time as you upgrade MediaWiki.

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If you have modified the skin or use a custom skin, you very likely will have to adjust it to work again with the new version of MediaWiki.
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{{Tip|1=<translate><!--T:124--> Instead of patching your "global" CSS and JS (JavaScript) files every time, you can simply add the code to your MediaWiki:Common.js and MediaWiki:Common.css pages. As these are part of the database which will be reused when you upgrade, you will not have to patch the MediaWiki core files any more.</translate>}}

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