In https://tracker.moodle.org/browse/MDL-76174 and https://tracker.moodle.org/browse/MDL-78618 there was a discussion about a SQL query that may be slow and cause Moodle to take a very long time opening "my courses".

A moodle instance I'm supporting has been experiencing this.

https://tracker.moodle.org/browse/MDL-78618 ends with 

• a post from misho (Mihail Peltekov) mentioning a patch by Atanas Georgiev: [^alternative-to-union-clause.patch]
• a comment from amaia (Amaia Anabitarte) mentioning "This issue is closed and the patch has been integrated in 4.1.5"

However, when I inspect the source code of Moodle 4.1.5 (as well as 4.1.9 and also 4.4), the patch by Atanas Georgiev has not been applied.

Probably, amaia was referring to a different patch as "being integrated in 4.1.5".

From what I can see, the SQL query that's being modified by the patch by Atanas Georgiev returns the same result in all circumstances, and in my tests with a Moodle instance using Mariadb and a different Moodle instance using Postgresql, the patch improves performance.

I therefore kindly ask you to consider integrating [^alternative-to-union-clause.patch] into the official Moodle source code.