> What is the preferred database to be used by wikidata?

The software behind Wikidata is called Wikibase [0]. As you can see in the requirements section there, it needs MySql, SQLite or PostGres. I am sure master (ie the latest dev version) currently works with the former two, though perhaps not with the later.

> I understand that MySQL is the default database for wikimedia but it is now slowly shifted to MariaDB.

If supports for MariaDB gets added to core and it's as complete as the MySQL support, I'd expect Wikibase to be automatically compatible, esp considering the similarity between the two RDBMS.

[0] https://www.mediawiki.org/wiki/Extension:Wikibase

Cheers

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Jeroen De Dauw
http://www.bn2vs.com
Don't panic. Don't be evil.
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