Grant MySQL/MariaDB privileges on all prefixed databases

Here we are, you reached this page while looking for how to grant MySQL/MariaDB privileges on some databases sharing the same table prefix like phabricator_asd, phabricator_lol or mediawiki_asd mediawiki_lol or whatever name prefixed with an underscore and you want to do it in the right way because you remember that something may be not correct in your syntax.


CREATE DATABASE mediawiki_asd;
CREATE DATABASE mediawiki_lol;

CREATE USER mediawiki_admin@localhost IDENTIFIED BY 'whoooo';

GRANT ALL PRIVILEGES ON `mediawiki\_%`.* TO mediawiki_admin@localhost;

In short you have to adopt \_% remembering to escape your underscores. Why? Because in the GRANT command you should respect the syntax expressed in the MariaDB LIKE specifications and that’s why your damn underscore, without being escaped, is a reserved char meaning whatever single character. The risk of not remembering this, is to forget the underscore escape, allowing all privileges also on unrelated databases like mediawikiasd or mediawikilol etc.
How could you sleep with such unuseful mistake? Uh?

Yep. I’ve written this dummy post because I’m definitely sick of wasting 5 minutes a week looking for this. Hoping to see this post in my DuckDuckGo results soon.

That’s all. asd

Is O_DIRECT in MySQL and MariaDB really effective?

While exploring some MySQL/MariaDB configurations i encountered the O_DIRECT option related to the innodb_flush_method directive.

So my question was. Is O_DIRECT really effective?

In short, your answer is maybe No… unless you have Solaris, but maybe it’s untrue even there.

I’ve found a very interesting lecture about this topic. This is my favorite extract:

In conclusion I can say that Linus Torvalds is once again corrent: O_DIRECT is completely useless and shouldn’t be used.

― svetlinmladenov on O_DIRECT

So, thank you Oracle! I wasted so much time because of your phrase in this stupid presentation:

InnoDB can use direct IO on systems that support it -Linux, FreeBSD, and Solaris–innodb_flush_method= O_DIRECT

Oracle Presentation, page 15

O_DIRECT = No thanks.